Patent Application: US-201414246518-A

Abstract:
monomers having a c - b - a - b - c structure are disclosed , where a is a core of either trithiocarbonate and allyl sulfide , where b are linker units , and where c are end units . the end units may comprise acrylates , methacrylates , alcohol , amine , and alkynes , among others . the linker units may include an alkane , alkene , phenyl , diphenyl , or benzylic group , among others . methods of synthesizing such compounds are also disclosed .

Description:
the invention may be further understood by the following non - limiting examples . in this paper , a mild and efficient synthesis of ( meth ) acrylate functionalized trithiocarbonates and allyl sulfides exhibiting controlled reversible addition - fragmentation termination ( craft ) monomers is described , and their efficiency in photoinduced stress relaxation during and post polymerization is demonstrated . the synthons consisted of an aft core ( a ) that was either an allyl sulfide or trithiocarbonate moiety . the linker ( b ) was synthetically connected to the aft core ( a ) and capped with an end group ( c ). the linkers included into the aft monomers were chosen to elicit specific mechanical behavior from the final networks and also to induce various electronic effects on the aft process . tailored at the ends of the aft monomers are ( c ) segments that consist generally of a polymerizable subunit , here , specifically an acrylate . the a , b , and c subunits that were systematically evaluated are presented in ( table 1 ). the key reaction to build the trithiocarbonate backbone used the reaction of carbon disulfide with a mild base , potassium carbonate , in a polar aprotic solvent with an alkyl halide , vinyl halide or benzylic halide , which contained a silyl protected alcohol at one end ( fig1 , scheme 1 ). the alcohol was subsequently deprotected using tbaf / acoh , which allows the use of fluorine to deprotect the silyl group without allylation of the aft core by tbaf . the deprotection is followed by a mitsunobu coupling to add the ( meth ) acrylate end groups ( fig1 , scheme 2 ). because of its unique self - healing properties , and the monomer is a methacrylate capped symmetrical molecule , s , s ′- bis ( isobutyric acid )- trithiocarbonate was synthesized to evaluate its properties against the newly formed trithiocarbonates . the allyl sulfides were synthesized as follows . to 3 - chloro - 2 - chloromethyl - 1 - propene was added the thio - alcohol in a solution of sodium methoxide . the thio - alcohols used were mercaptoethanol , thiophenol , and 4 - hydroxyl - 4 ′- mercaptobiphenyl . 4 - hydroxyl - 4 ′- mercaptobiphenyl was synthesized from 4 - iodoanisol and 4 - bromothioanisol via a kumada coupling . the product was subsequently reduced with sodium ethanethiolate to yield the 4 - hydroxyl - 4 ′- mercaptobiphenyl ( fig1 , scheme 3 ). once all the thio - alcohols were in hand , the core allyl disulfide scaffold was formed . the acrylate or methacrylate was added to the pendent alcohol using modified schotten - baumann conditions , where the acyl chloride is reacted with the alcohol using triethylamine as an acid scavenger . ( fig2 , scheme 4 ). the acid chloride reaction to produce the diester acrylate functionality was used because the ease of the reaction conditions and the cost of acryloyl chloride . the reaction can be done using mitsunobu conditions , as well . the mitsunobu reaction gives overall better yields , but the purification of the final product is difficult since the dead and triphenylphosphine bi - products are hard to separate from the final product . the monomers were incorporated into polymer networks to evaluate each monomer &# 39 ; s individual effects on the polymer network . for the acrylate functionalized aft synthons , a polymer network can be formed either by a photocatalyzed radical polymerization or by a base ( or nucleophile ) catalyzed thiol - michael addition reaction ( fig4 a , 4 b ). the trithiocarbonate networks were constructed using a base catalyzed thiol - michael “ click ” reaction by reacting stoichiometric mixtures ( 1 : 1 acrylate : thiol functional group ratio ) of pentaerytheritol tetrakis ( 3 - mercaptopropionate ) ( petmp ) and tetraethylene glycol diacrylate ( tegda ) and the raft trithiocarbonate . the craft monomer containing networks conversion and kinetics were evaluated for 60 minutes by ir spectroscopy after the addition of 1 % triethylamine as the thiol - michael catalyst ( fig5 ). the allyl sulfide networks were constructed using the same base catalyzed thiol - michael “ click ” reaction by reacting stoichiometric mixtures ( 1 : 1 acrylate : thiol functional group ratio ) of pentaerytheritol tetrakis ( 3 - mercaptopropionate ) ( petmp ) and tetraethylene glycol diacrylate ( tegda ) and the allyl sulfide the craft monomer containing networks conversion and kinetics were evaluated for 60 minutes by ir spectroscopy after the addition of 1 % triethylamine or 0 . 8 % imidazole as the thiol - michael catalyst , respectively ( fig6 ). the previously made thio - michael networks were evaluated on a dynamic mechanical analyzer ( dma ) to analyze the how the different monomers affected the glass transition and elastic moduli of the networks ( table 2 ). in the thiol - michael catalyzed networks , the trithiocarbonates showed a reduced rate of conversion as the monomers became bulkier and more rigid . on the other hand , the phenyl allyl sulfide network was made with 0 . 8 % imidazole , where the allyl alkyl sulfide network was formed from 1 % triethylamine . the pk a of imidazole is 7 . 0 compared to that of triethylamine , which is 11 . 0 . even with a base that is 10 , 000 times less basic , the rate of conversion of the phenyl substituent was only slightly slower that than the alkyl allyl sulfide with triethylamine . this phenomenon can be accounted for by the stabilization of the thiol - michael anion intermediate by the resonance of the phenyl ring . the rubbery moduli of the networks showed little difference between the craft monomers used in the network . the only significant difference in modulus was seen in the s , s ′- bis ( isobutyric acid )- trithiocarbonate network . due to the step - growth thiol - michael network formation , the resins made from these networks traditionally have tg &# 39 ; s below 0 ° c . with the incorporation of the pi groups , especially the phenyl ring systems , the pi - pi stacking greatly increases the tg &# 39 ; s of the networks containing these molecular interactions . stress relaxation properties were evaluated for the craft monomers by incorporating them into an elastomeric network containing 1 % photoinitiator ( dmpa ). the networks were constructed using a base catalyzed thiol - michael “ click ” reaction by reacting stoichiometric mixtures of multifunctional thiols and acrylate - based craft monomers . utilizing this non - photo , non - radical mediated polymerization mechanism , the photointiator is unconsumed during the polymerization and is present to induce post - polymerization photo - induced stress relaxation without degrading or changing the crosslink density of the networks . the craft monomer containing networks were evaluated on a dma by inducing a strain of 10 %, irradiating at 20 mw / cm 2 , and evaluating the evolution of stress relaxation in the network . the craft monomers exhibited stress relaxation results that varied from 9 %- 73 % under these conditions ( table 3 ) the trithiocarbonates , upon irradiation , showed remarkable stress relaxation in a controlled manner . we hypothesize that these stress relaxation results are indicative of the cleavage rate due to the leaving radical stability i 3 , as seen in fig1 and 21 , and the relative rate with which i 3 will attack another craft center ( c m ). the new craft monomers were evaluated for their stress relaxation ability relative to a control monomer / polymer , s , s ′- bis ( r , r ′- dimethyl - r ″- acetic acid )- trithiocarbonate dimethacrylate , which was synthesized using a procedure from literature [ 10 , 22 ] ( fig7 ) and relative to networks that did not contain any craft monomers . in post stress relaxation studies , we hypothesize that the stability of the leaving carbon radical i 3 in the trithiocarbonate systems dominates their ability to relax stress due to the stability of the trithiocarbonate radical intermediate , which can be evaluated . the stress relaxation data suggests this effect is not as prevalent in the allyl sulfide systems , where the radical intermediate is not as stable as its trithiocarbonate counterpart , and the leaving radical is a more stable sulfur radical , not a carbon radical . for post stress relaxation , we believe these factors are what allow the same allyl sulfide radical generated to alleviate more stress in comparison to its trithiocarbonate counterpart ( fig8 ). however , in the allyl sulfide biphenyl system , it is hypothesized that over - enhanced radical stability in the leaving group , i 3 , generates a radical that attacks neighboring centers , c m , so slowly that little relaxation in the network is seen . with the understanding of these two competing mechanisms , craft agents can be designed to rapidly alleviate the stress in a system . it is also noteworthy to mention the incorporation of different functional groups into the craft monomers , and how these modifications affect network properties . the incorporation of alkene , phenyl , and biphenyl linkers within the system have not only radical stabilizing merit , but these functional groups permit pi interactions within the network that effect the t g and elastic modulus ( e ′) of these networks ( table 2 ). craft monomers were formulated into a chain - growth polymerization network . the monomers were evaluated on their ability to affect the polymerization rate and conversion of an acrylate polymerization system , as raft monomers . the monomers incorporated were specifically designed to affect the raft mechanism and thereby their ability to control the polymerization . the chain - growth system contained 70 wt % bisphenol a ethoxylated diacrylate , 28 . 5 - 20 wt % tetraethylene glycol diacrylate , and 10 - 1 . 5 wt % of the trithiocarbonate craft monomers . the craft concentrations were selected so that the rate retardation observed due to the craft monomers did not alter the overall conversion of the polymerization below 70 % conversion ( fig9 ). the allyl sulfide craft monomers were formulated in the same networks as the trithiocarbonate monomers . it is well known that the allyl sulfide containing compounds are non - reversible . after the two central sulfur atoms have been released during the chain transfer process , the compounds reach an equilibrium with the surrounding monomers , and the chain transfer process no longer dictates the polymerization process . due to the lack of reversibility of the aft allyl sulfides , the allyl sulfide monomers were incorporated in concentrations of 10 wt % in the chain - growth polymerization experiments ( fig1 ). in fig1 the control was the monomer solution that contained strictly the acrylate monomers with no raft component . without wishing to be bound by any particular belief , we believe the unique rate retardation properties of the craft monomer in the acrylate chain - growth polymerizations are due to two major factors . the first factor relates to the stability of the radical leaving group . this has been described by thang and co - workers as the k b . 3 the rate of β - scission of the intermediate to generate the leaving radical , ( r ), is a factor in the control of the polymerization rate . the linker incorporated into each monomer was chosen specifically to affect the stability of the leaving radical . the more stable the leaving radical the greater the chain transfer properties of the monomer . secondly , the efficiency of the leaving radical , ( r ), to attack another trithiocarbonate radical and facilitate the chain transfer process is also believed to be a factor . as predicted , the trithiocarbonates with their ability to have fully reversible afct show the greatest reduction in shrinkage stress during an in - situ polymerization . the trithiocarbonates by rate retardation are able to control the amount of stress relaxation extremely efficiently in the chain polymerizations . the alkene trithiocarbonate showed the greatest stress relaxation with only 1 . 5 % bw ( by weight ) loading . in the chain polymerization , the alkene trithiocarbonate was able to reduce stress evolution by 77 %. the allyl sulfides were not as efficient in reducing stress evolution in chain polymerization . this can be explained by the inability of the allyl sulfides to be completely reversible afct agents and that the attack of the thiyl radical on carbon centers is not as efficient . the best allyl sulfide was the phenyl allyl sulfide that showed 50 % stress reduction at 10 % bw loading in the monomer formulation . the newly synthesized craft monomers were subsequently evaluated in their ability to reduce stress evolution during in - situ polymerization . the monomers ability to reduce stress evolution were evaluated by a tensometer . fig1 a - 11b and 12 a - 12 b show results for shrinkage stress over time and conversion over time for trithiocarbonate monomers and allyl sulfide monomers , respectively ( the control was the monomer mixture with no raft component ). the newly synthesized craft monomers were also evaluated in their ability to reduce stress evolution during mixed - mode polymerization . the monomers ability to reduce stress evolution were evaluated by a tensometer . fig1 a - 13b and 14 a - 14 b show results for shrinkage stress over time and conversion over time for trithiocarbonate monomers and allyl sulfide monomers , respectively ( the control was the monomer mixture with no raft component ). the trithiocarbonates by rate retardation are able to control the amount of stress relaxation extremely efficiently in the chain - step polymerizations . the alkene trithiocarbonate showed the greatest stress relaxation with only 1 . 5 % bw loading . in the chain - step growth polymerization , the alkene trithiocarbonate was able to reduce stress evolution by 82 %. in the mixed mode ( chain - step growth ) polymerization , the allyl sulfides perform much better as afct agents . the introduction of petmp allows for thiyl radicals to have a greater affinity for the allyl sulfides and increase their ability to be reversible and promote chain transfer . the phenyl allyl sulfide was able to reduce the stress by 82 % with a 10 % loading in the mixed mode monomer formulation . methods and equipment : the shrinkage stress and functional group conversion were simultaneously observed during polymerization using a tensometer coupled with a ftir ( nicolet 670 ), which was equipped with near - infrared transmitting optical fiber patch cables and an indium gallium arsenide ( ingaas ) detector . the tensometer was developed by the paffenbarger research center ( american dental association health foundation ) to measure the stress during photopolymerization . stress evolution is measured by the cantilever beam deflection that is detected by the lvdt ( linear variable displacement transducer ). in the tensometer , one glass rod is fixed to the bottom plate and another rod is connected to the cantilever beam . the formulated resin was injected between the two glass rods , which results in a specimen geometry of 6 mm diameter and 1 mm thickness . samples were irradiated with 365 nm filtered uv light at 5 mw / cm2 ( acticure 4000 , expo ) for 10 min . evolution of the acrylate and methcrylate double bond concentrations were determined by monitoring the infrared absorption peaks centered at 6200 cm - 1 ( c ═ c — h stretching , overtone ). the post polymerization stress relaxation studies , the elastic moduli ( e ′) and glass transition temperatures ( tgs ) of polymerized samples were measured by dynamic mechanical analysis ( dma , ta instruments q800 ) ( table 2 ). for post polymerization stress relaxation studies , specimens ( 10 mm × 3 mm × 0 . 5 mm ) for dma were prepared and strained at a rate of 0 . 5n / min until a constant strain of 10 . 0n was achieved . the samples were held for 2 minutes to alleviate any viscoelastic creep in the networks . following the two minutes hold , the samples were irradiated for 30 minutes using 365 nm light at 20 mw / cm 2 . the samples were restrained to 15 . 0n to ensure there were no viscoelastic or cross - linking changes in the network . nmr spectra were acquired on a bruker avance - iii 400 nmr spectrometer system operating at 400 . 13 mhz for 1h observation . solvent chemical shifts were referenced through mesternova from j . org . chem . 1997 , 62 , 7512 - 7515 . the uv - vis was employed using a diode array double - beam spectrophotometer with ebert monochromator ( evolution 300 , thermo - scientific , west palm beach , fla .). absorption spectra were collected in quartz cuvettes with a 1 cm pathlength . mass spectrometry was done on a synapt g2 high definition mass spectrometer ( waters company ). the esi - ms settings are as follows : capillary voltage : 2 . 8 kv ( positive mode ), − 2 . 2 kv ( negative mode ); sampling cone voltage : 20 - 40v depending on the molecular weight . ( the higher the mw , the higher the sampling cone ); extraction cone : 4 . 0v ; source temperature : 80 ° c . ; desolvation temperature : 150 ° c . ; desolvation gas ( n2 ): 600 l / h 2 . the samples were scanned for molecular ion analysis using esi by dissolving or diluting the sample in meoh or meoh / dcm ( 50 : 50 ), and infusing the sample in q - tof ms with 5 ul / min flow rate to acquire the data . experimental section : materials : 3 - chloro - 2 - chloromethyl - 1 - propene , mercaptoethanol ( 99 %), 3 -( tert - butyl ) dimethyl silyl - 1 - bromopropane , 4 - bromocrotonoate , dibal - h , diethyl azodicarboxylate , triphenylphosphine , tbdmsci , imidazole , tetrabutyl ammonium fluoride , glacial acetic acid , 4 - hydroxythiophenol , 4 - iodoanisol , 4 - bromothioanisole , triethylamine (& gt ; 99 %), acryloyl chloride , sodium metal ( 99 %) and ethylene glycol dimercaptopropoinate ( egdmp ), tetraethylene glycol diacrylate , ( tegda ), carbon disulfide , potassium carbonate , n , n - di - methylformamide , acetonitrile , n , n - dimethyl acetamide , hexanes , ethyl acetate , methanol , dry tetrahydrofuran ( 99 . 5 %), dry dichloromethane ( 99 . 5 %), p - chlorobenzyl chloride , and all other chemicals unless specified were obtained from sigma aldrich . pentaerythritol tetrakis ( 3 - mercaptopropionate ), ( petmp ), was obtained from evans chemetics . irgacure 651 ( 2 , 2 - dimethoxy - 2 - phenylacetophenone - dmpa were obtained from basf ( formally ciba ). all chemicals were used without further purification . compound 1 : to a solution of dry dmf ( 100 ml = 1m solution concentration ) under n 2 and degassed for 30 minutes was added potassium carbonate ( 14 . 5 g , 105 mmol ) and carbon disulfide ( 8 . 37 g , 110 mmol ). the reaction was stirred vigorously for 15 minutes . the solution turned a deep blood - red color . to the solution was added 3 -( tert - butyl ) dimethyl silyl - 1 - bromopropane ( 26 . 5 g , 105 mmol ), and the reaction turned an immediate yellow color . the reaction was heated to 40 c for 24 hours . the reaction showed 40 % conversion by nmr analysis . to the reaction was added another 0 . 5 eq of carbon disulfide . the reaction was monitored by nmr , and over time small portions of cs 2 and k 2 co 3 were added until the reaction was complete by nmr . a total of 2 . 5 eq of carbon disulfide and 1 . 5 eq of potassium carbonate were added to the reaction . the reaction was quenched with 250 ml of water and taken up in ethyl acetate ( 500 ml ). the organic layer was washed with water ( 250 ml × 3 ) and brine ( 250 ml ). the organic layer was dried over sodium sulfate , filtered , and reduced in vacuo to yield a crude yellow oil . the oil was purified by flash chromatography in a gradient fashion 100 % hexanes to 99 : 1 hexanes / ethyl acetate to yield 22 . 18 g of pure product . yield 93 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 3 . 69 ( t , j = 8 hz , 4h ), 3 . 45 ( t , j = 8 hz , 4h ), 1 . 91 ( p , j = 8 hz , 4h ), 0 . 90 ( s , 18h ), 0 . 06 ( s , 12h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 224 . 63 ( c ═ s ), 61 . 62 ( c4 ), 33 . 62 ( c2 ), 31 . 23 ( c3 ), 26 . 08 ( c7 ), 18 . 45 ( c6 ), 5 . 19 ( c5 ); ms ( esi , m / z ): [ m + na ] + calcd for c 19 h 42 o 2 s 3 si 2 , 477 . 2 ; found , 477 . 2 . compound 2 : to a solution of the silyl - protected alkyl trithiocarbonate ( 22 . 18 g , 48 . 75 mmol ) in thf ( 487 ml = 0 . 1m ) at 0 c under n 2 was added acoh ( 6 . 44 g , 2 . 2 eq ) and tbaf ( 107 ml , 107 mmol ). the reaction was allowed to warm up to rt overnight . after 24 hrs , the reaction was reduced in vacuo , and the organic layer was taken up in 500 ml of ethyl acetate . the organic layer was washed with water ( 250 ml × 3 ) and brine ( 250 ml ). the organic layer was dried over sodium sulfate , filtered , and reduced in vacuo to yield a crude yellow oil . the oil was purified by flash chromatography in a gradient fashion 40 %: 60 % ethyl acetate / hexanes to 60 : 40 ethyl acetate / hexanes to afford 7 . 12 g of a pure yellow oil . yield 65 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 3 . 70 ( t , j = 8 hz , 4h ), 3 . 48 ( t , j = 8 hz , 4h ), 2 . 28 ( s , oh , 2h ), 1 . 94 ( p , j = 8 hz , 4h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 225 . 25 ( c ═ s ), 61 . 04 ( c4 ), 33 . 43 ( c2 ), 31 . 19 ( c3 ); ms ( esi , m / z ): [ m + na ] + calcd for c 7 h 14 o 2 s 3 , 249 . 0 ; found , 249 . 0 . compound 3 : to a solution of compound 2 ( 5 . 0 g , 22 . 1 mmol ) in thf ( 220 ml ) was added triphenylphosphine ( 20 . 27 g , 77 . 3 mmol ) and acrylic acid ( 5 . 3 ml , 3 . 5 eq ). the solution was cooled to 0 c and placed under n 2 . to the reaction was added 40 % dead ( 35 . 21 ml , 3 . 5 eq ) dropwise . after 1 hour , the reaction was warmed to 25 c and allowed to stir 16 hours . the reaction was diluted with hexanes and cooled to 0 c to precipitate the triphenylphosphine oxide bi - product . the reaction was filtered and reduced in vacuo to a crude yellow oil . the oil was purified by flash chromatography in a gradient fashion using 100 % hexanes to 85 : 15 hexanes / ethyl acetate to afford 6 . 52 g of the product . yield 89 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 6 . 42 ( dd , 2h ), 6 . 13 ( dd , 2h ), 5 . 85 ( dd , 2h ), 4 . 24 ( t , j = 8 hz , 4h ; ch 2 ), 3 . 46 ( t , j = 8 hz , 4h ; ch 2 ), 2 . 09 ( p , j = 8 hz , 4h , ch 2 ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 223 . 47 ( c ═ s ), 166 . 15 ( c5 ), 131 . 18 ( c7 ), 128 . 36 ( c6 ), 63 . 04 ( c4 ), 33 . 33 ( c2 ), 27 . 66 ( c3 ); uv - vis ( methanol ): λ max ( ε )= 430 nm ( 27000 ); ms ( esi , m / z ): [ m + na ] + calcd for c 13 h 18 o 4 s 3 , 357 . 0 ; found , 357 . 0 . compound 4 : the following molecule was synthesized from either 4 - bromocrotonoate or methyl trans - 4 - bromo - 2 - butenoate . to 4 - bromocrotonoate ( 25 g , 139 . 66 mmol ) in a solution of diethyl ether ( 500 ml ) at − 78 c under n 2 was added 1m dibal - h in hexanes ( 350 ml , 2 . 5 eq ). the dibal - h was added through an addition funnel dropwise over 3 - 4 hrs . the reaction was warmed to 0 c , and the reaction was stirred for an additional hour before being quenched with 40 ml of acoh . the reaction was warmed to rt and filtered over celite . the product was reduced in vacuo , and the crude yellow oil ( appr . 22 g ) was carried forward immediately to be tbdms protected due to the instability of the intermediate . to a solution of the 4 - bromo - 2 - butenol ( 22 g , 145 . 69 mmol ) and imidazole ( 19 . 84 g , 291 . 39 mmol ) in dcm ( 730 ml ) at 0 c under n 2 was added tbdmsci ( 32 . 93 g , 1 . 5 eq ) in 3 portions over 30 minutes . the reaction was allowed to warm up to room temperature overnight . after 12 hours , the reaction was complete by tlc . the reaction was filtered , washed with 1n hcl ( 1 × 100 ml ), water ( 2 × 100 ml ), brine ( 1 × 200 ml ), and dried over sodium sulfate . the organic layer was filtered and reduced in vacuo to yield 32 . 4 g of a crude material . the crude was purified by fc using 100 % hexanes to yield 23 g of the desired product . yield 62 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 5 . 89 ( m , 2h ), 4 . 21 ( m , 2h ), 3 . 98 ( dt , 2h ), 0 . 93 ( s , 9h ), 0 . 09 ( s , 6h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 134 . 63 ( c3 ), 125 . 78 ( c2 ), 62 . 57 ( c4 ), 32 . 36 ( c1 ), 25 . 91 ( c7 ), 18 . 36 ( c6 ), 5 . 26 ( c5 ); ms ( esi , m / z ): [ m + h ] + hr calcd for c 10 h 21 bro 2 si , 265 . 1 ; found , 265 . 1 . compound 5 : to a solution of silyl - protected bromo - alkene ( 26 . 84 g , 101 . 2 mmol ) in n , n - dimethylacetamide ( 200 ml ) was added carbon disulfide ( 15 . 42 g , 202 . 4 eq ) and potassium carbonate ( 27 . 96 g , 202 . 4 mmol ). the reaction was placed under inert atmosphere and heated to 40 c for 24 hours . the reaction was cooled to 25 c and quenched with water . the aqueous layer was extracted with methylene chloride . the organic layer was washed with water , brine , and dried over sodium sulfate . the organic layer was reduced in vacuo to a crude yellow oil . the oil was purified by flash chromatography 95 : 5 hexanes / ethyl acetate to yield 8 . 12 g of the silyl protected alkene trithiocarbonate . yield 34 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 5 . 79 ( m , 4h ), 4 . 15 ( m , 4h ), 4 . 03 ( m , 4h ), 0 . 90 ( s , 18h ), 0 . 06 ( s , 12h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 222 . 87 ( c ═ s ), 135 . 09 ( c4 ), 122 . 57 ( c3 ), 63 . 17 ( c5 ), 38 . 88 ( c2 ), 26 . 08 ( c8 ), 18 . 54 ( c7 ), 5 . 07 ( c6 ); ms ( esi , m / z ): [ m + na ] + calcd for c 21 h 42 o 2 s 3 si 2 , 501 . 2 ; found , 501 . 2 . compound 6 : to a solution of the compound 5 ( 8 . 12 g , 16 . 98 mmol ) in thf ( 200 ml ) at 0 c under n 2 was added acoh ( 3 . 0 ml , 50 . 94 mmol ) and tbaf ( 43 ml , 42 . 5 mmol ). the reaction was allowed to warm up to rt overnight . after 16 hrs , the reaction was reduced in vacuo to yield a crude yellow oil . the oil was purified by flash chromatography in a gradient fashion 40 %: 60 % ethyl acetate / hexanes to 60 : 40 ethyl acetate / hexanes to afford 3 . 8 g of a pure yellow oil . yield 89 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 5 . 93 ( m , 2h ), 5 . 77 ( m , 2h ), 4 . 14 ( m , 4h ), 4 . 05 ( dq , 4h ), 1 . 39 ( d , oh , 2h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 222 . 38 ( c ═ s ), 134 . 55 ( c4 ), 124 . 39 ( c3 ), 63 . 0 ( c5 ), 38 . 59 ( c2 ); ms ( esi , m / z ): [ m + li ] + calcd for c 9 h 14 o 2 s 3 , 257 . 0 ; found , 257 . 0 . compound 7 : to a solution of compound 6 ( 5 . 0 g , 19 . 96 mmol ) in thf ( 220 ml ) degassed under n 2 at 0 c was added triphenylphosphine ( 18 . 33 g , 70 eq ) and acrylic acid ( 5 . 03 g , 70 mmol ). to the reaction was added dead 40 % in toluene ( 32 ml , 70 mmol ) dropwise over 30 minutes . the reaction was allowed to warm to rt and stir overnight . the triphenylphosphine oxide salts were precipitated out with hexanes . the oil was purified by flash chromatography using 10 : 90 ethyl acetate / hexanes to yield 2 . 25 g of the trans - trans isomer . yield 33 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 6 . 42 ( dd , 2h ), 6 . 12 ( dd , 2h ), 5 . 86 ( m , 6h ), 4 . 63 ( m , 4h , ch 2 ), 4 . 05 ( dt , 4h , ch 2 ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 221 . 94 ( c ═ s ), 165 . 88 ( c6 ), 131 . 26 ( c8 ), 129 . 26 ( c7 ), 128 . 31 ( c4 ), 127 . 51 ( c3 ), 64 . 15 ( c5 ), 38 . 43 ( c2 ); uv - vis ( methanol ): λ max ( ε )= 420 nm ( 34000 ); ms ( esi , m / z ): [ m + na ] + calcd for c 15 h 18 o 4 s 3 , 381 . 0 ; found , 381 . 0 . compound 8 : the following molecule was synthesized from 4 -( chloromethyl ) benzyl alcohol ( 15 g , 96 mmol ) in a solution of dcm ( 500 ml ), whereas the concentration of the solution was 0 . 19m , at o c under n 2 was added imidazole ( 16 . 31 g , 239 mmol ). the reaction was allowed to stir for 15 minutes . to the reaction was added tbdmsci ( 18 . 76 g , 125 mmol ). the solution was allowed to warm to room temperature overnight . after 16 hours , the reaction was filtered . the organic layer was washed with 1n hcl ( 100 ml ), di water ( 100 ml × 3 ), and brine ( 100 ml ). the organic layer was dried over sodium sulfate and filtered . the product was reduced in vacuo , and the crude clear oil was purified by flash chromatography using 100 % hexanes to yield 23 . 12 g of pure product . 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 34 ( m , 4h ), 4 . 75 ( s , 2h ), 4 . 59 ( s , 2h ), 0 . 95 ( s , 9h ), 0 . 11 ( s , 6h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 141 . 99 ( ar — c5 ), 136 . 20 ( ar — c2 ), 128 . 66 ( ar — c3 ), 126 . 46 ( ar — c4 ) 64 . 75 ( c6 ), 46 . 34 ( c1 ), 26 . 10 ( c9 ), 18 . 57 ( c8 ), 5 . 11 ( c7 ); ms ( esi , m / z ): [ m + na ] + calcd for c 14 h 23 closi , 293 . 1 ; found , 293 . 1 . compound 9 : to a solution of dry acetonitrile ( 100 ml = 1m solution concentration ) under n 2 and degassed for 30 minutes was added potassium carbonate ( 11 . 8 g , 85 . 3 mmol ) and carbon disulfide ( 6 . 82 g , 89 . 6 mmol ). the reaction was stirred vigorously for 15 minutes . to the solution was added ( 23 . 12 g , 85 . 3 mmol ), and the reaction turned an immediate yellow color . the reaction was heated to 40 c and allowed to react for 48 hours . the reaction showed complete conversion by nmr analysis . the reaction was reduced in vacuo to yield a pure yellow solid . the yield of the reaction was quantitative in yield . 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 30 ( m , 8h , ar — h ), 4 . 73 ( s , 4h ), 4 . 62 ( s , 4h ), 0 . 96 ( s , 18h ), 0 . 11 ( s , 12h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 222 . 95 ( c ═ s ), 141 . 26 ( ar — c6 ), 133 . 49 ( ar — c3 ), 129 . 27 ( ar — c4 ), 126 . 46 ( ar — c5 ), 64 . 73 ( c7 ), 41 . 49 ( c2 ), 26 . 08 ( c10 ), 18 . 53 ( c9 ), 5 . 13 ( c8 ); ms ( esi , m / z ): [ m + na ] + calcd for c 29 h 46 o 2 s 3 si , 601 . 2 ; found , 601 . 2 . compound 10 : to a solution of the benzyl trithiocarbonate ( 22 . 1 g , 38 . 2 mmol ) in dcm ( 550 ml ) at 0 c under n 2 was added acoh ( 8 . 03 g , 3 . 5 eq ) and tbaf ( 114 ml , 114 mmol ). the reaction was allowed to warm up to rt overnight . after 24 hrs , the reaction was ceased . the organic layer was washed with water ( 250 ml × 2 ), 1n hcl , and brine ( 250 ml ). the organic layer was dried over sodium sulfate , filtered , and reduced in vacuo to yield a crude yellow solid . the solid was purified by flash chromatography in a gradient fashion 30 %: 70 % ethyl acetate / hexanes to 100 % ethyl acetate to afford 9 . 65 g of a pure yellow solid . yield 72 %. 1 h nmr ( 400 mhz , dmso - d6 , δ ): 7 . 30 ( m , 8h , ar — h ), 5 . 18 ( t , oh , 2h ), 4 . 65 ( s , 4h ), 4 . 47 ( d , 4h ); 13 c nmr ( 400 mhz , dmso - d6 , δ ): 222 . 55 ( c ═ s ), 142 . 14 ( c6 ), 133 . 27 ( c3 ), 129 . 01 ( c4 ), 126 . 769 ( c5 ), 62 . 59 ( c7 ), 40 . 40 ( c2 ); ms ( esi , m / z ): [ m + na ] + calcd for c 17 h 18 o 2 s 3 , 373 . 1 ; found , 373 . 1 . compound 11 : to a solution of crf - 2 - 15 ( 5 . 0 g , 14 . 3 mmol ) in thf ( 160 ml ) degassed under n 2 was added triphenylphosphine ( 13 . 1 g , 49 . 9 mmol ) and acrylic acid ( 3 . 6 g , 49 . 9 mmol ). the reaction was cooled to 0 c and dead 40 % in toluene ( 22 . 73 ml , 49 . 9 mmol ) was added dropwise . after an hour the reaction was warmed to room temperature and stirred for 24 hours . the reaction was diluted with hexanes to precipitate the triphenylphosphine oxide by - product and was filtered . the crude solid was purified by flash chromatography using 80 : 20 ethyl acetate / hexanes to yield 6 . 51 g of a yellow waxy solid . yield 99 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 32 ( m , 8h , ar — h ), 6 . 44 ( dd , 2h ), 6 . 15 ( dd , 2h ), 5 . 84 ( dd , 2h ), 5 . 17 ( s , 4h ), 4 . 60 ( s , 4h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 222 . 28 ( c ═ s ), 165 . 96 ( c ═ o ), 135 . 52 ( c3 ), 135 . 16 ( c6 ), 131 . 27 ( c10 ), 129 . 50 ( c4 ), 128 . 59 ( c5 ), 128 . 22 ( c9 ), 65 . 90 ( c7 ), 41 . 11 ( c2 ); uv - vis ( methanol ): λ max ( ε )= 430 nm ( 45401 ); ms ( esi , m / z ): [ m + na ] + calcd for c 23 h 22 o 4 s 3 , 481 . 1 ; found , 481 . 1 . the intermediate was synthesized by kumada coupling of 4 - bromothioanisole and 4 - iodoanisole . a grignard solution was prepared by adding mg turnings ( 2 . 87 g , 118 . 2 mmol ) and catalytic i 2 to 4 - bromothioanisole ( 20 . 0 g , 98 . 5 mmol ) under n 2 . the solution was gently refluxed in 200 ml of thf until only trace mg metal was present in the reaction mixture . the solution was cooled and placed into an addition funnel under n 2 . to a solution of 4 - iodoanisole ( 23 . 05 g , 98 . 5 mmol ) and palladium triphenylphosphine tetrakis ( 1 . 14 g , 0 . 98 mmol ) in 200 ml of refluxing thf under n 2 was added the above grignard solution dropwise . after one hour the addition was complete and mg salts began to crash out of the reaction solution . the solution was refluxed for an additional hour and then cooled to rt . the reaction was poured into a solution of ice and 1n hcl . the solution immediately became cloudy and a precipitate formed . the precipitate was filtered , washed with water , and dried in vacuo . the crude material was recrystallized from 1 : 1 hexane / ipa to yield 16 . 52 g of pure compounds . yield 78 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 51 ( m , 4h , ar — h ), 7 . 33 ( m , 2h , ar — h ), 6 . 99 ( m , 2h , ar — h ), 3 . 86 ( s , 3h , och 3 ), 2 . 53 ( s , 3h , sch 3 ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 159 . 21 ( c2 ), 137 . 82 ( c6 ), 136 . 82 ( c5 ), 133 . 14 ( c9 ), 127 . 93 ( c8 ), 127 . 21 ( c4 ), 127 . 15 ( c7 ), 114 . 35 ( c3 ), 55 . 43 ( c1 ), 16 . 141 ( c10 ); ms ( esi , m / z ): [ m + li ] + calcd for c 14 h 14 os , 231 . 1 ; found , 231 . 1 . to a solution of 4 - methoxy - 4 ′ methylthiobiphenyl ( 16 . 0 g , 69 . 5 mmol ) in 275 ml dmf under n 2 was added sodium thiosulfate ( 14 . 6 g , 2 . 5 eq ). the solution was heated to a gentle reflux overnight . the solution was quenched with a solution of ice water with 50 ml of 1n hcl . the crude solid was filtered , dried , and recrystallized from 1 : 1 : hexanes / ipa to yield 11 . 52 g of product . 81 . 9 % yield . 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 48 ( m , 4h , ar — ch ), 7 . 32 ( m , 2h , ar — ch ), 6 . 88 ( m , 2h , ar — ch ), 2 . 50 ( s , 2h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 157 . 6 ( c1 ), 138 . 9 ( c5 ), 138 . 4 ( c4 ), 133 . 7 ( c8 ), 130 . 3 ( c7 ), 128 . 7 ( c3 ), 127 . 7 ( c6 ), 114 . 3 ( c2 ), 55 . 4 ( c9 ), 16 . 1 ( c10 ); ms ( esi , m / z ): [ m − h ] − calcd for c 12 h 10 os , 201 . 0 ; found , 201 . 0 . to a solution of meoh at 0 c under n 2 was added na metal ( 1 . 03 g , 45 mmol ). the reaction was slowly allowed to warm to room temperature . 4 - hydroxy - 4 ′ mercaptobiphenyl ( 8 . 0 g , 40 mmol ) was added to the reaction , and the reaction was heated to reflux . 3 - chloro - 2 - chloromethyl propene ( 2 . 25 g , 18 mmol ) was added dropwise over an hour , and the reaction was allowed to reflux overnight . the solution was reduced in vacuo and purified by flash chromatography 20 : 80 acetone / hexanes to yield 3 . 92 g of the pure allyl sulfide . yield 47 . 7 %. 1 h nmr ( 400 mhz , dmso - d6 , δ ): 9 . 56 ( s , 2h , ar — oh ), 7 . 46 ( m , 8h , ar — h ), 7 . 33 ( m , 4h , ar — h ), 6 . 82 ( m , 4h , ar — h ), 5 . 06 ( s , 2h , c ═ ch 2 ), 3 . 8 ( s , 4h ); 13 c nmr ( 400 mhz , dmso - d6 , δ ): 157 . 13 ( c1 ), 139 . 57 ( c10 ), 137 . 92 ( c5 ), 133 . 15 ( c8 ), 129 . 97 ( c4 ), 129 . 52 ( c7 ), 127 . 43 ( c3 ), 126 . 24 ( c6 ), 116 . 55 ( c11 ), 115 . 71 ( c2 ) 36 . 89 ( c9 ); ms ( esi , m / z ): [ m − h ] − calcd for c 28 h 24 o 2 s 2 , 455 . 1 ; found , 455 . 1 . to a solution of the biphenyl allyl sulphide ( 3 . 5 g , 7 . 67 mmol ) in 77 ml of thf at 0 c under n 2 was added triethylamine ( 2 . 67 ml , 2 . 5 eq ). the solution was stirred for 5 minutes and then acryloyl chloride ( 1 . 55 ml , 2 . 5 eq ) was added dropwise . the solution was allowed to warm to room temperature and stir overnight . the solution was filtered and reduced in vacuo to a crude solid . the solid was purified by flash chromatography to yield 1 . 82 g . yield 42 %. 1 h nmr ( 400 mhz , acetone d - 6 , δ ): 7 . 66 ( m , 4h , ar — h ), 7 . 58 ( m , 2h , ar — h ), 7 . 43 ( m , 2h , ar — h ), 7 . 24 ( m , 2h , ar — h ), 6 . 57 ( dd , 2h ), 6 . 39 ( dd , 2h ), 6 . 10 ( dd , 2h ), 5 . 12 ( s , 2h ), 3 . 88 ( s , 4h ); 13 c nmr ( 400 mhz , acetone d - 6 , δ ): 165 . 05 ( c3 ), 151 . 47 ( c4 ), 141 . 16 ( c13 ), 138 . 91 ( c8 ), 138 . 80 ( c7 ), 136 . 49 ( c11 ), 133 . 29 ( c1 ), 130 . 91 ( c10 ), 129 . 04 ( c2 ), 128 . 65 ( c6 ), 128 . 28 ( c9 ), 123 . 20 ( c5 ), 117 . 39 ( c14 ), 38 . 48 ( c12 ); ms ( esi , m / z ): [ m + na ] + calcd for c 34 h 28 o 4 s 2 , 587 . 10 ; found , 587 . 10 . the allyl sulfides were synthesized as follows . to a 1 l flask at 0 c was added 600 ml of methanol . the solution was kept under 30 c as na metal ( 19 g , 0 . 83 mol ) was added in small portions . after all the sodium had reacted , 2 - mercaptoethanol ( 57 . 8 g , 2 . 2 eq ) was added to the solution of sodium methoxide . the solution was heated to reflux and 3 - chloro - 2 - chloromethyl - 1 - propene ( 42 g , 1 eq ) was added dropwise over 1 hour . the solution was allowed to reflux overnight . the solution was cooled to 25 c , filtered , and reduced in vacuo to remove the methanol . the crude material was taken up in 500 ml &# 39 ; s of water and extracted with ether ( 4 × 150 ml ). the ether layer was washed with brine and dried over sodium sulfate . the organic layer was reduced in vacuo . the crude light - yellow oil was purified by vacuum distillation to yield 65 g of the mbh . yield 92 . 3 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 5 . 00 ( s , 2h ), 3 . 68 ( t , 4h ), 3 . 29 ( s , 4h ), 2 . 67 ( s , oh , 2h ), 2 . 61 ( t , 4h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 140 . 31 ( c ═ ch 2 ), 116 . 14 ( c5 ), 60 . 31 ( c1 ), 34 . 85 ( c3 ), 33 . 55 ( c2 ). to mbh ( 50 g , 1 eq ) under n 2 at 0 c was added freshly distilled methylene chloride and triethylamine ( 53 . 42 g , 2 . 2 eq ). after 30 minutes of degassing with n 2 , acryloyl chloride ( 40 ml , 47 . 78 g , 2 . 2 eq ) was added dropwise over 3 hours . the reaction was warmed to 25 c and allowed to stir overnight . the organic layer was washed with water , brine , and dried over magnesium sulfate . the organic layer was filtered and reduced in vacuo to a brownish - yellow crude oil . the oil was purified by flash chromatography 70 : 30 hexanes / ethyl acetate to yield an off - colored oil 46 g . yield 60 . 5 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 6 . 40 ( dd , 2h ), 6 . 10 ( dd , 2h ), 5 . 83 ( dd , 2h ), 5 . 04 ( s , 2h ), 4 . 26 ( t , 4h ), 3 . 32 ( s , 4h ), 2 . 67 ( t , 4h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 166 . 03 ( c ═ o ), 140 . 40 ( c7 ), 131 . 39 ( c1 ), 128 . 35 ( c2 ), 116 . 85 ( c8 ), 63 . 33 ( c4 ), 35 . 47 ( c6 ), 29 . 41 ( c7 ). to a 1 l flask at 0 c was added 160 ml of methanol . the solution was kept under 30 c as na metal ( 5 . 10 g , 221 . 24 mmol ) was added in small portions . after all the sodium had reacted , 4 - hydroxythiophenol ( 25 . 0 g , 2 . 2 eq ) was added to the solution of sodium methoxide . the solution was heated to reflux and 3 - chloro - 2 - chloromethyl - 1 - propene ( 11 . 26 g , 1 eq ) was added dropwise over 1 hour . the solution was allowed to reflux overnight . the solution was cooled to 25 c , filtered , and reduced in vacuo to remove the methanol . the crude material was taken up in 500 ml of water and extracted with ether ( 4 × 150 ml ). the ether layer was washed with 1n hcl , water , brine , and dried over sodium sulfate . the organic layer was reduced in vacuo to a crude orange oil . the oil was purified by flash chromatography 90 : 10 hexanes / ethyl acetate to yield 23 . 52 g of a colorless oil . yield 85 . 8 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 23 ( m , 4h , ar — h ), 6 . 74 ( m , 4h , ar — h ), 5 . 84 ( s , 2h , ar — oh ), 4 . 70 ( s , 2h , c ═ ch 2 ), 3 . 57 ( s , 4h , ch 2 ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 155 . 3 ( c1 ), 140 . 45 ( c10 ), 138 . 6 ( c5 ), 134 . 3 ( c8 ), 132 . 7 ( c4 ), 126 . 0 ( c7 ), 116 . 5 ( c3 ), 116 . 0 ( c6 ), 40 . 63 ( c11 ); ms ( esi , m / z ): [ m + li ] + calcd for c 16 h 16 o 2 s 2 , 344 . 3 ; found , 344 . 3 . to compound 18 ( 23 . 52 g , 1 eq ) under n 2 at 0 c was added freshly distilled methylene chloride and triethylamine ( 17 . 2 g , 2 . 2 eq ). after 30 minutes of degassing with n 2 , acryloyl chloride ( 15 . 38 g , 2 . 2 eq ) was added dropwise over 1 hours . the reaction was warmed to 25 c and allowed to stir overnight . the organic layer was washed with 1n hcl , sodium bicarbonate , water , brine , and dried over magnesium sulfate . the organic layer was filtered and reduced in vacuo to an orange oil . the oil was purified by flash chromatography 95 : 5 hexanes / ethyl acetate going to 90 : 10 hexanes / ethyl acetate to yield an off - colored oil 12 . 82 g . yield 40 . 2 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 7 . 35 ( m , 4h , ar — h ), 7 . 06 ( m , 4h , ar — h ), 6 . 59 ( dd , 2h ), 6 . 30 ( dd , 2h ), 6 . 00 ( dd , 2h ), 4 . 91 ( s , 2h ), 3 . 69 ( s , 4h ); 13 c nmr ( 400 mhz , cdcl 3 , δ ): 164 . 29 ( c ═ o ), 149 . 44 ( c4 ), 139 . 65 ( c9 ), 133 . 02 ( c1 ), 132 . 72 ( c6 ), 131 . 75 ( c2 ), 127 . 82 ( c5 ), 122 . 01 ( c10 ), 39 . 17 ( c9 ); ms ( esi , m / z ): [ m + na ] + calcd for c 22 h 20 o 4 s 2 , 435 . 04 ; found , 435 . 04 . the compound was synthesized from a literature procedure [ 8 ]. the flask was charged with s , s ′- bis ( α , α ′- dimethyl - α ″- acetic acid )- trithio - carbonate ( 2 . 78 g , 9 . 8 mmol ) and triphenylphosphine ( 9 . 03 g , 34 . 5 mmol ) and subsequently deoxygenated by purging with nitrogen for 30 min . 2 - hydroxyethyl methacrylate ( 4 . 48 g , 34 . 5 mmol ) and anhydrous tetrahydrofuran ( 110 ml ) were added . the flask was immersed in an ice bath , and cooled to 0 c . a solution of diethyl azodicarboxylate ( 15 . 7 ml , 34 . 5 mmol ) was added dropwise . the reaction was warmed to rt and stirred for 16 hours . the reaction was diluted with hexanes and the triphenylphosphine oxide salts were filtered off . the filtrate was reduced in vacuo to a crude red oil . the oil was purified by flash chromatography 90 : 10 hexanes / ethyl acetate to yield 2 . 8 g of the trithiocarbonate . yield 56 %. 1 h nmr ( 400 mhz , cdcl 3 , δ ): 6 . 11 ( dd , 2h ), 5 . 57 ( dd , 2h ), 4 . 33 ( s , 8h ), 1 . 93 ( s , 6h ), 1 . 63 ( s , 12h ); 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