bluuebunny/crossref_metadata_2025_split huggingface dataset:
The photooxidation of mono‐ and dimethylnaphthalenes by singlet oxygen
Authors: van den Heuvel C. J. M. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractThe reactions of singlet oxygen with all possible isomers of mono‐ and dimethylnaphthalenes as well as with 1,4,6,7‐tetramethylnaphthalene have been studied. Apart from 2‐methylnaphthalene, which does not react under our reaction conditions, attack on 1,4‐ and in some cases also on 5,8‐positions results in the formation of endoperoxides (epidioxides). In the case of 1,4‐dihydro‐2,3‐dimethyl‐1,4‐epidioxynaphthalene there is a subsequent reaction step with singlet oxygen which introduces an allylic hydroperoxy function.The structures of the endoperoxides were established by means of NMR. A simple volumetric method was employed to measure the relative reaction rates. Rate constants (15°C) for the mono‐ and dimethylnaphthalenes vary over a range of 103 M−1s−1. The differences in reactivity can be logically explained by the activating effect of the methyl substituents.On heating, the endoperoxides decompose quantitatively back to starting materials.
Sigma‐assistance, an unrecognized factor in organic reactivity
Authors: Verhoeven J. W. 
Published: September 2010

AbstractA simple perturbational frontier molecular orbital description with inclusion of sigma electrons is presented for bifunctional intramolecular reactivity. This description readily accounts for the preferred formation of odd membered rings in (di) radical cyclization and of even membered transition states in intramolecular hydrogen or hydride migration.
Coordination and activation of the NS bond in sulfurdiimines RNSNR and sulfinylanilines RNSO by metal atoms
Authors: Vrieze Kees , van Koten Gerard 
Published: September 2010

AbstractA survey is given of the coordination chemistry of sulfurdiimines RNSNR and sulfinylanilines RNSO towards metal atoms. It is shown that these pseudoallene ligands which are isostructural and isoelectronic with SO2 may coordinate via N, S or via the π‐NS double bond. Nitrogen coordination is favoured by metals in the higher oxidation states e.g. PtII, PdII, but may also occur for Rh1 and If and even for zerovalent metals such as Cr°, Mo° and W°. Sulfur coordination probably occurs for Cr°, Mo° and W°, but has been observed for Rh1 and Ir1. Finally, metal‐π‐N=S bonding is clearly favoured by electron‐rich metal atoms like Ni°, Pd°, Pt°, Rh1 and Ir1. In the case of metal‐ π2‐N=S coordination of the RNSNR ligands further reactions may occur which lead to NS bond rupture. Such bond rupture may result in a large number of reactions varying from simple insertion of a metal atom into an N‐S bond to the formation of RNS, S and NR fragments which are captured in metal cluster complexes. Other ways of converting the RNSNR ligand involve the reactions with LiR′, R′MgX and trialkylaluminium compounds. The anionic RNS(R′)NR ligand so formed may behave as a bridging ligand but, more interestingly, as a pseudoallylic chelate group. It is shown that RNS(R′)NR− bonded as a chelate to transition metal atoms decomposes stereospecifically into azo compounds and SR− fragments.
Oxidation of (‐)‐2‐bromo‐3‐hydroxy‐N‐methyl‐6‐oxomorphinan with Fremy's salt. An unprecedented 2,4‐shift of the bromo substituent. (Chemistry of opium alkaloids, Part XIII)
Authors: Olieman C. , Maat L. , Beyerman H. C. 
Published: September 2010

Abstract(‐)‐3‐Hydroxy‐N‐methyl‐6‐oxomorphinan (6a) and its (‐)‐2‐bromo derivative (6b) were converted into (‐)‐2,3‐dihydroxy‐N‐methyl‐6‐oxomorphinan (8a) and its (‐)‐4‐bromo derivative (8b), respectively, by oxidation with Fremy's salt to the ortho‐quinones, followed by reduction. Methylation of 8a and 8b gave the corresponding methyl ethers 9a and 9b. Catalytic hydrogenolysis of 8b and 9b gave 8a and 9a, respectively. The structure of (‐)‐2,3‐dimethoxy‐N‐methyl‐6‐oxomorphinan (9a) was confirmed by total synthesis, and that of (‐)‐4‐bromo‐2,3‐dimethoxy‐N‐methyl‐6‐oxomorphinan (9b) by single‐crystal X‐ray analysis.The model compound 2‐bromo‐4,5‐dimethylphenol (15) gave, analogously, 3‐bromo‐4,5‐dimethyl‐pyrocatechol (16).
Sulfenylation of dithio ester anions
Authors: Sukhai R. S. , de Jong R. , Meijer J. , Brandsma L. 
Published: September 2010

AbstractThe anions derived from dithio esters 1 react with alkyl alkanethiosulfonates in 1,2‐dimethoxyethane to give the S‐sulfenylated products 3. Nucleophilic reagents like potassium tert‐butoxide, dithio ester anions or ‐ in some cases ‐ even (liquid) ammonia catalyse the rearrangement of 3 into the C‐sulfenylated compounds 4. The latter compounds can be isolated directly, if the dithio ester anions 2 are allowed to react with thiosulfonates in liquid ammonia or with thiocyanates in dimethoxyethane or liquid ammonia.
Geminal carbon‐proton spin‐spin coupling constants in ethyl, isopropyl and tert‐butyl compounds
Authors: Spoormaker Tom , de Bie Marius J. A. 
Published: September 2010

AbstractThe geminal 13C1H coupling constants in ethyl, isopropyl and tert‐butyl compounds having elements of the first row of the Periodic Table and halogens as substituents are determined by single resonance 13C FT NMR spectroscopy. In addition, the values of directly bonded 13C13C coupling constants are given. The substituent electronegativity dependence of the geminal 13C1H coupling constant is discussed. It is concluded that the influence exerted by a β‐methyl substituent on the geminal 13C1H coupling constant of 13Cα‐Cβ‐1H fragments is not constant and hence no simple additivity relation can be established for this coupling constant.
The electrochemical Wittig‐Horner reaction; evidence of a stepwise cleavage of a four‐membered ring Wittig intermediate
Authors: van Tilborg W. J. M. , Smit C. J. 
Published: September 2010

AbstractElectro‐reduction of diethyl(trichloromethyl)phosphonate in the presence of aldehydes or ketones replaces the oxygen atom of the carbonyl group by a dichloromethylene group. The yield of 1,1‐dichloroethene product decreases substantially if the carbonyl compound carries strongly acidic hydrogen. In several cases the conversion of the four‐membered ringWittigintermediate into its corresponding carbanion by heterolytic PC bond cleavage is observed. The intermediate carbanion is sufficiently stable to be intercepted by proton abstraction. These observations suggest that, at least with our substrates, the decomposition of theWittigfour‐membered ring intermediate occurs along a two‐step path way.
Texture of zeolites and zeolite‐containing solids
Authors: Aneke L. E. , de Jong W. A. , van den Berg P. J. 
Published: September 2010

AbstractTexture studies, in which specific surface area and total pore volume were determined by low temperature nitrogen adsorption, were carried out on a number of porous solids, ranging from cation‐exchanged Y‐zeolites, impregnated with β‐AlF3 and copper, to steamed silica‐alumina. The zeolites were impregnated with β‐AlF3 and Cu in order to improve their Toluene disproportionation performance.After comments on the applicability of the conventional approaches to zeolites and zeolite‐containing solids, a new method is proposed for calculating of the surface area of this class of compounds. This method makes use of the micropore volume, determined by De Boer's t‐method, and the surface area and volume of a zeolite cage, calculated from X‐ray data.
The photo‐oxidation of hexamethylbenzene and pentamethylbenzene by singlet oxygen
Authors: van den Heuvel C. J. M. , Hofland A. , Steinberg H. , de Boer Th. J. 
Published: September 2010

AbstractIn a two step reaction, hexamethylbenzene consumes two molecules of singlet oxygen to form epidioxy hydroperoxide 3. The first step involves a [4 + 2]‐cycloaddition, which is followed by an ene‐reaction. The structure of the intermediary endoperoxide 2 has been established spectroscopically. Pentamethylbenzene reacts in the same way with singlet oxygen, albeit much more slowly. Two epidioxy hydroperoxides are formed in this case.
Triplet‐sensitized interconversion and photooxygenation of Vitamin D and trans‐Vitamin D
Authors: Gielen J. W. J. , Koolstra R. B. , Jacobs H. J. C. , Havinga E. 
Published: September 2010

AbstractTriplet‐sensitized irradiation of either Vitamin D or transVitamin D establishes a photo‐equilibrium between the two isomers, the position of which varies with the triplet energy of the sensitizer. In the presence of oxygen, selective photooxygenation of trans‐Vitamin D takes place. The applicability of sensitization for the preparation of cis‐ and trans‐Vitamin D and derivatives thereof is shown.
Nickel(II) complexes of deprotonated thiourea; Crystal structure of Ni[(C6H5)NC(S)N{(C2H4)2O}]2
Authors: Janakiram‐Sayala Chhaya , Bosman W. P. , Willemse J. , Cras J. A. 
Published: September 2010

AbstractNickel(II) complexes with deprotonated trisubstituted thiourea were prepared. The crystal structure of Ni[PhNC(S)N{(C2H4)2O}]2 showed that the nickel atom is centrosymmetrically square planar coordinated through the N and S of the thioureido ligands. The diamagnetic compound crystallizes in the monoclinic space group C2/c [a = 24.146(3), b = 10.480(2), c = 9.473(3) Å, β = 106.38(1)°] and contains four formula units per unit cell.
10‐Mono‐, 11‐mono‐, 12‐mono and 11,12‐dideuteroretinal
Authors: Broek A. D. , Lugtenburg J. 
Published: September 2010

AbstractThe 11‐mono and 12‐mono‐ and 11,12‐dideuteroretina1 (in the all‐trans, 9‐cis, 11‐cis and 13‐cis form) with > 98% chemical purity and > 95% mono‐ and dideuterium incorporation were prepared using the same scheme for all three compounds. The all‐trans, 9‐cis and 13‐cis‐10‐monodeuteroretinal isomers were prepared with good chemical purity (> 99%) and 82% monodeuterium incorporation via a different reaction scheme.
Enzymatic synthesis of a peptide bond between a tryptic fragment of horse heart cytochrome c and a synthetic model peptide
Authors: Westerhuis L. W. , Tesser G. I. , Nivard R. J. F. 
Published: September 2010

AbstractAs a model study for the usefulness of the synthetic action of a proteinase in the semisynthesis of large polypeptides, a heme peptide, comprising the residues 1‐38 of horse heart cytochrome‐c and bearing protective functions on the ϵ‐amino groups, was incubated with trypsin in the presence of H‐Orn(Msc)‐Trp‐NHCH3 in a mixture of water and organic solvents. We found that the proteolytic enzyme catalysed the formation of a peptide bond between the fragment and the dipeptide derivative.
Tautomeric pyridines. Part XXIV. Tautomeric equilibria for 3‐ethoxycarbonyl‐, 3‐ethoxycarbonyl‐6,7‐methylenedioxy‐, and 3‐cyano‐4‐quinolone
Authors: Katritzky Alan R. , Ellison Joan , Frank Judit , Mészáros Zoltán 
Published: September 2010

AbstractUltraviolet spectra and pKa values for the title compounds and their O‐ and N‐ethyl derivatives show that in each case the quinolone form is favoured in aqueous solution. The results are compared qualitatively with those for 4‐quinolone and for findings in the gas phase.
An improved synthesis of 1,2,3‐butatrienyl ethers
Authors: Visser R. G. , Bos H. J. T. , Brandsma L. 
Published: September 2010

AbstractA modified synthetic route to 1,2,3‐butatrienyl ethers 3 is presented. It involves hydroxyalkylation of 2‐propynyl ethers with an aldehyde or a ketone, followed by trimethylsilylation of the hydroxy ether 1 and 1,4‐elimination of Me3SiOH from 2 with ethyllithium.
Application of levulinic acid ester as a protective group in the synthesis of oligosaccharides
Authors: Koeners H. J. , Verhoeven J. , van Boom J. H. 
Published: September 2010

AbstractThe fast, selective and mild removal of levulinoyl groups with hydrazine from galactose, which also carries hydroxyl functions protected with acetyl groups, enabled us, under Koenigs‐Knorr conditions, to synthesize tri‐ and tetrasaccharides containing β‐linked galactose and glucose units. Selective acylation of the primary alcoholic group of the partially protected galactose derivative 13b with levulinic acid was achieved in good yield. The preparation of tetrasaccharide 18b, having a free hydroxyl function, was effected by condensing dimer 16b with the bromo derivative 17, followed by the removal of the levulioyl group with hydrazine.
An additivity relation for carbon‐13 chemical shifts in substituted allenes
Authors: Janssen R. H. A. M. , Ch. Lousberg R. J. J. , de Bie M. J. A. 
Published: September 2010

AbstractAn empirical method for the calculation of the carbon chemical shifts of allene carbons is developed. The method is successful in predicting the chemical shifts in a wide variety of substituted allenes.The effect of the electronegativity of substituents, with respect to the chemical shift contributions, is discussed.Experimental chemical shift increment values show a linear correlation with both the calculated diamagnetic shielding effects and the Pauling electronegativities for first row elements of the periodic system directly attached to the allene.
R3Cu2M species: Convenient cuprates for the conversion of 1‐alkynes into 1‐alkenes
Authors: Westmijze H. , Kleijn H. , Meijer J. , Vermeer P. 
Published: September 2010

AbstractThe paper describes reactions of 1‐alkynes, R1‐C≡C‐H, with new cuprate species of the type R3Cu2M [M = Mg(Cl, Br)]. Under suitably chosen conditions a smooth transfer of R (Me or Et) from the cuprates to the 1‐alkynes (R1 = Ph or n‐C6H13) could be realized. The resulting stereospecifically generated adducts [(RR1CCH)xCu2R3‐x]Mg (Cl or Br) were stable under the conditions of the reactions, provided that a sufficient amount of lithium bromide was present. In the absence of lithium bromide substantial decomposition of the adducts into RR1CCH‐CHCRR1 took place. During the reaction of PhC≡CH with Me3Cu2Li the addition reaction was accompanied by deprotonation, which could be proved by using PhC≡CD as starting alkyne. Deprotonation in PhC≡CH as side‐reaction also occurred with Me3Cu2MgBr. The latter complex was prepared from MeMgBr and CuBr.The number of R groups which are transferrable from R3Cu2M to R1‐C≡CH with an acceptable rate appeared to depend on the nature of R, viz. One R group in the case of Me3Cu2M and all three R groups in the case of Et3Cu2M.
Conformational studies on helicenes VI. A comparison between experimental and calculated conformations
Authors: Somers J. B. M. , Borkent J. H. , Laarhoven W. H. 
Published: September 2010

AbstractThe force‐field method of Warshel has been used for the calculation of the conformations of hexahelicene, two methyl substituted hexahelicenes and heptahelicene. The calculated models have been compared with the known X‐ray structure and the generally small differences have been discussed.The method has also been used for the calculation of the structure of 5,6‐dihydrohexahelicene. The dihedral angles in the aliphatic moiety of the model agree reasonably well with those calculated from NMR data.
4,4‐(Ethylenedithio)pentanoyl: A masked levulinoyl protective group in the synthesis of oligosaccharides
Authors: Koeners H. J. , Verdegaal C. H. M. , van Boom J. H. 
Published: September 2010

AbstractIn this study we demonstrate that the 4,4‐(ethylenedithio)pentanoyl group can be used for the protection of hydroxyl functions of glucose and galactose. Selective acylation of the primary alcoholic function of the galactose derivative 1a was accomplished using 4,4‐(ethylenedithio)pentanoyl chloride. Furthermore, we show that the 4,4‐(ethylenedithio)pentanoyl group can easily be converted into the levulioyl group and that the dithio‐acetal function is stable under the conditions required for the formation of interglycosidic linkages. Finally, a combined use of the levulinoyl and the 4,4‐(ethylenedithio)pentanoyl group enabled us to synthesize a branched tetrasaccharide containing glucose and galactose moieties.
Photochemistry of dienones. Part IX. Photochemistry of (E)‐ and (Z)‐α‐ionone
Authors: Visser Cornelis P. , Cerfontain Hans 
Published: September 2010

AbstractThe photochemical reactions of (E)‐α‐ionone (1) and its photoproducts have been re‐examined. Upon irradiation with λ 254 and 313 nm a sequence of photo‐reactions takes place: initially (Z)‐α‐ionone (2) is formed and subsequently (E)‐ and (Z)‐retro‐α‐ionone (4a and b), which eventually undergo a 1,3‐ and 1,5‐acyl shift to give 3‐acetyl‐2,4,4‐trimethyl‐3‐ (5) and 6‐acetyl‐1,3,3‐trimethyl‐2‐vinylcyclohexene (6), respectively. Evidence is presented for the intermediacy of the photo‐enol 3a in the photoconversion of the α‐ionone to retro‐α‐ionone. The multiplicities of the reacting excited states for the (E) → (Z)‐α‐ionone and the α‐ionone → retro‐α‐ionone conversions (using triplet photosensitization) and for the 1,5‐acyl shift of retro‐α‐ionone (using CIDNP) have been shown to be triplet, singlet, and singlet, respectively. Upon irradiation of 1 with λ 366 nm, instead of the shorter wavelengths, the reaction stops at the (E)‐ and (Z)‐retro‐α‐ionone stage. Variation in the solvent did not alter the course of the photoconversion.
Studies on polypeptides XXXVI. Chemical semisynthesis of a ribonuclease A analogue ([13‐isoleucine, 20‐homoserine] ‐ ribonuclease A)
Authors: Hoogerbout P. , Kerling K. E. T. 
Published: September 2010

AbstractThe peptide bond formation between synthetic [Ile13, Hse20]‐S‐peptide lactone and S‐protein leads to the formation of [Ile13, Hse20]‐RNase A. Coupling yields up to 7 % were obtained.
Base‐catalysed isomerization of 2‐propynylamines. Synthesis of (dialkylamino)allenes
Authors: Verkruijsse H. D. , Bos H. J. T. , de Noten L. J. , Brandsma L. 
Published: September 2010

AbstractA number of (dialkylamino)allenes 2 have been obtained in excellent yields and in a reasonable state of purity by isomerization of dialkyl‐2‐propynylamines 1 with potassium tert‐butoxide in tetrahydrofuran or with the complex t‐BuOK.t‐BuOH in hexamethylphosphoric triamide. Treatment of the 2‐propynylamines with t‐BuOK in dimethyl sulfoxide leads to equilibrium mixtures of the allenic amines 2 and dialkyl‐1‐alkynylamines 3.
The bromination and iodination of N1‐substituted uracils
Authors: Bakker Cees N. M. , Kaspersen Frans M. 
Published: September 2010

AbstractReaction of N1‐substituted uracils with bromine in water at pH 7 leads to 5‐bromo‐6–hydroxy‐5,6‐dihydrouracils. For different N1‐substituents these products were isolated and the relatively stable derivatives were characterized by 1H NMR and mass spectroscopy. On electrophilic iodination with [131I]iodide and chloramine‐T in water no indications were obtained for the formation of such dihydrouracils except for uridine and deoxyuridine. However, on reaction of N1‐substituted uracils with N1‐iodosuccinimide in CHCl3 containing ethanol or in ethanol, 5‐iodo‐6‐ethoxy‐5,6‐dihydrouracils could be isolated as reaction products.
1,3‐Dipolar cycloadditions to alkyldicyanamides
Authors: Benders P. H. , Reinhoudt D. N. , van den Ham D. M. W. 
Published: September 2010

AbstractThe 1,3‐dipoles 2,4,6‐trimethylbenzonitrile oxide and benzyl azide react with alkyldicyanamides (1) to give the 3,5‐disubstituted 1,2,4‐oxadiazoles 2 and the 1,5‐disubstituted tetrazole 4, respectively, by (3 + 2)‐cycloaddition. The structure of 4 has been determined by a single crystal X‐ray analysis.
Base‐induced isomerization of 1,4‐dialkoxy‐2‐alkynes
Authors: van Rijn P. E. , Everhardus R. H. , van der Ven J. , Brandsma L. 
Published: September 2010

Abstract1,4‐Dialkoxy‐2‐alkynes of structural types ROCH(R1)CCCH2 OR (R and R1 = alkyl) and ROC(R1)(R2)CCCH2OR (R = alkyl, R1 and R2 = alkyl or R1R2C(CH2)5) are converted into the allenic isomers under the influence of potassium tert‐butoxide in dimethyl sulfoxide. 1,4‐Dialkoxy‐2‐butynes RO‐CH2CCCH2OR under these conditions yield conjugated dienes of the type ROCHCHCHCHOR; the corresponding allenes, ROCHCCHCH2OR, can be prepared by using potassium tert‐butoxide in tetrahydrofuran or liquid ammonia.
Intérêt des spectres de RMN de 13C dans la série de la triazine‐,2,4
Authors: Daunis J. , Djouai‐Hifdi L. , Follet M. 
Published: September 2010

AbstractL'étude d'environ 60 spectres de RMN de 13C de dérivés de la triazine montre qu'il est possible de déterminer leur structure isomère ou tautomère qui est liée à la nature et à la position des substitutions.
Synthesis and properties of 1,1′‐methylene‐2,2′‐dipyrrolyl ketone
Authors: de Groot J. A. , Koek J. H. , Lugtenburg J. 
Published: September 2010

Abstract1,1′‐methylene‐2,2′‐dipyrrolyl ketone can be conveniently prepared in high yield, starting from pyrrole, in three steps. It shows extreme properties that are not observed in comparable rigid ketone systems. These chemical and physical properties can be explained assuming mesomeric forms with charge separation resulting from the electron rich pyrrole rings and the rigidity of the system. The fluorescence quantum yield is 0.07 and the fluorescence lifetime is 27 ns.
The electrosynthesis of carboxylic acids from carbon dioxide and butadiene
Authors: van Tilborg W. J. M. , Smit C. J. 
Published: September 2010

AbstractElectroreduction of carbon dioxide in acetonitrile in the presence of butadiene gives rise to the formation of 3‐pentenoic acid (2), 3‐hexenedioic acid (3), and 3,7‐deca‐dienedioic and two isomeric C10‐dicarboxylic acids (4) in high chemical yields.
Chemistry of crown ethers (XVI). A safe and efficient procedure for the isolation and purification of crown ethers by complex formation with alkaline earth metal alkanedisulfonates
Authors: de Jong F. , Reinhoudt D. N. , van Zon A. , Torny G. J. , van de Vondervoort E. M. 
Published: September 2010

AbstractA safe, efficient and selective method has been developed for the isolation and purification of crown ethers to replace the conventional procedure, which involves repeated vacuum distillations and has reportedly led to destructive explosions. The method is based on the formation of an insoluble 1:1 complex upon stirring a solution of a crown ether in an organic solvent with solid metal salts of 1,n‐alkanedisulfonic acids, such as barium and strontium methanedisulfonate and barium 1,2‐ethanedisulfonate. This extraction procedure can be applied to several crown ethers (including 18‐crown‐6) dissolved in a variety of solvents. Almost quantitative recovery of the crown ether is achieved by continuous extraction with nitromethane.The usefulness of the method was illustrated by isolating 18‐crown‐6 from the crude mixture obtained in the course of its preparation. Whereas conventional workup (including two distillation steps) gave a 25% yield of pure 18‐crown‐6, the CH2(SO3)2Ba‐based method gave a yield of 34%.
Conversion of sterically hindered phenols into the corresponding N,N‐dimethylarenesulfonamides via the Newman‐Kwart rearrangement
Authors: Wagenaar Anno , Engberts Jan B. F. N. 
Published: September 2010

AbstractThe 2‐alkyl‐ and 2,6‐dialkylbenzenesulfonyl chlorides 5a‐f were obtained in high yield by chlorination of the correspondingly substituted S‐aryl N,N‐dialkylthiocarbamates 4a‐g. These precursors have been synthesized via the Newman‐Kwart rearrangement of the corresponding O‐aryl N,N‐dialkylthiocarbamates 3a‐g, which are easily prepared from the sterically hindered phenols 1a‐g. The sulfonyl chlorides 5a‐f are readily transformed into the desired 2‐alkyl‐ and 2,6‐dialkyl‐N,N‐dimethylbenzenesulfonamides 6a‐f.
Preparation of deuterium‐labelled retinals having high deuterium content on specific positions 10‐Mono‐, 11‐mono‐, 10,11‐di‐ and 14,20,20,20‐tetradeuterioretinal
Authors: Broek A. D. , Lugtenburg J. 
Published: September 2010

Abstract10‐Mono‐, 11‐mono‐ and 10,11‐dideuterioretinal (in the all‐trans, 9‐cis, 11‐cis and 13‐cis forms) of > 98% purity and the required (> 96%) deuterium incorporation were prepared via LiAlH4 or LiAlD4 reduction of the retinylidene derivative 8. Compound 8 was prepared by coupling β‐ionone with 6,6‐dimethoxy‐4‐methyl‐3‐hexen‐1‐yne (6), which had been obtained in high yield from 2‐propynyl bromide and commercial 4,4‐dimethoxy‐2‐butanone (4). Exchange of 4 with D2O and base gave 4,4‐dimethoxy‐1,1,1,3,3‐pentadeuterio‐2‐butanone (4a), which in turn, using the same synthetic method, finally provided 14,20,20,20‐tetradeuterioretinal.