bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of Ph(ClCH2)SiH2 with fluoride ion sources: Formation of fluorine‐terminated siloxanes
Authors: Huhmann Jean L. , Corey Joyce Y. 
Published: January 2005

AbstractThe fluoride ion‐induced rearrangement of Ph(ClCH2)SiH2 was expected to provide either PhMeSiHF (migration of hydride) or (PhCH2)SiH2F (migration of phenyl). However, when Bu4N+F− (commercial TBAF) is added to Ph(ClCH2)SiH2, a mixture of fluorine‐terminated siloxanes, FPhMeSiO(PhMeSiO)xSiMePhF, is obtained. The presence of the Me group suggests a rapid anion‐induced migration of hydride to produce PhMeSiHF which reacts further with water present in TBAF samples. When the reaction mixture is cooled to 0°C or is monitored at the early stage of the reaction, the major products are PhMeSiF2, PhMeSi(OH)F, PhMeSi(OH)2, and FPhMeSiOSiMePhF which are proposed as the building blocks for the siloxanes. When dried CsF in CH3CN is used, the major products are PhMeSiF2 and PhMeSiH2 which are assumed to form from the fluoride ion‐induced disproportionation of PhMeSiHF. The reaction chemistry is rationalized in terms of hypervalent intermediates. The fluoride ion‐induced reactions of PhMeSiH2 and PhMeSiCl2 are also described and compared to those of Ph(ClCH2)SiH2.
Simple preparation of sterically congested 1,9‐disubstituted dibenzothiophenes and formation of their dithia dications via transannular S‐S interaction
Authors: Kimura Takeshi , Horie Yoji , Ogawa Satoshi , Furukawa Naomichi , Iwasaki Fujiko 
Published: January 2005

Abstract4,6‐Disubstituted thianthrene‐5‐oxides reacted with n‐butyllithium to afford sterically crowded 1,9‐disubstituted dibenzothiophenes (3) in moderate yields. The structures of the phenylthio derivative 3a and its monooxide 6a were determined by X‐ray crystallographic analysis, which revealed that the distances between the two outer sulfur atoms are 3.012 Å (3a) and 3.016 Å (6a). 1,9‐Disubstituted dibenzothiophenes 3 and their monooxides 6 afforded the corresponding dithia dications on dissolution in conc. sulfuric acid. The lower oxidation potentials of compounds 3 compared with other dibenzothiophene derivatives reveal evidence for strong transannular interaction between the two outer sulfur atoms.
A facile synthesis of 2‐cyano‐4H‐3,1‐ benzothiazines and 2‐cyano‐4H‐3,1‐benzoxazines
Authors: Lee Hyunil , Kim Kyongtae 
Published: January 2005

AbstractTreatment of the hydrochloride salts of 4‐chloro‐5‐(2‐halomethylaryl‐imino)‐5H‐1,2,3‐dithiazoles (2) with sodium cyanoborohydride in THF at room temperature gave 2‐cyano‐4H‐3,1‐benzothiazines (1) in good to moderate yields. 2‐Cyano‐4H‐3,1‐benzoxazines (4) were obtained in good to moderate yields by refluxing of 4‐chloro‐5‐(2‐hydroxymethylarylimino)‐5H‐1,2,3‐dithiazoles (3) with sodium hydride in THF. Intermolecular reaction of 5‐(p‐tolylimino)‐5H‐1,2,3‐dithiazole (12) with benzyl alcohol under the same conditions gave the acyclic analog of 4.
Preparation and X‐ray crystal structure analysis of cis‐2, 4‐bis(2, 4, 6‐tri‐t‐butylphenyl)‐1, 2, 4‐oxadiphosphetane 2, 4‐disulfide and cis/trans isomerization of the corresponding 1, 2, 4‐thiadiphosphetane derivative
Authors: Toyota Kozo , Ishikawa Yasuhisa , Shirabe Kotaro , Yoshifuji Masaaki , Okada Kengo , Hirotsu Ken 
Published: January 2005

Abstract1,3‐Bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphaallene (1) reacted with elemental sulfur under wet reaction conditions to give cis‐ and trans‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,2,4‐thiadiphosphetane 2,4‐disulfide (cis‐2 and trans‐2) and cis‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,2,4‐oxadiphosphetane 2,4‐disulfide (cis‐3). The structure of cis‐3 was determined by X‐ray crystallography, and the cis/trans isomerization of 2 was studied.
A new rearrangement in phosphorus chemistry
Authors: Shevchenko Igor V. , Schmutzler Reinhard 
Published: January 2005

AbstractThe oxidation of 1,5‐dimethyl‐2,4‐bis(diethylamino)‐1,5‐diaza‐2,4‐diphosphorinan‐6‐one5with tetrachloroorthobenzoquinone (TOB) leads to the formation of the spirophosphorane9, which is unstable and undergoes an unusual spontaneous rearrangement into the isomeric methylenephosphinophosphorane11. The sulfuration of9and11gives the stable isomers12and19, exhibiting no tendency of mutual transformation. The mechanism of the isomerization of9into11is discussed. Some chemical properties of9and11have been investigated.
Synthesis of 1λ4,2‐diselenol‐1‐ylium salts
Authors: Reid David H. , Rose Beate G. , Jackson Michael G. 
Published: January 2005

AbstractSeven bis‐(1λ4,2‐diselenol‐1‐ylium) tetrachloroferrates have been prepared by reaction of 1,3‐diketones or 1,3‐ketoaldehydes with hydrogen selenide and iron(III) chloride in ethanol saturated with hydrogen chloride. They decompose gradually in air. The corresponding 1λ4,2‐diselenol‐1‐ylium perchlorates have been prepared by reaction of the tetrachloroferrates with perchloric acid in acetic acid and are stable. The tetrachloroferrates react with benzenediazonium tetrafluoroborate to give 6,6aλ4‐diselena‐1,2‐diazapentalenes.
Synthesis of silyl, germyl, and phosphino‐substituted acylketenes from pivaloylethoxyacetylene
Authors: Lukashev Nikolai V. , Fil'chikov Aleksei A. , Kazankova Marina A. , Beletskaya Irina P. 
Published: January 2005

AbstractThe reaction of pivaloylethoxyacetylene with silicon halides, which has been found to occur as a 1,4‐addition, leads to allenic ethers, which readily eliminate ethyl halides and are converted to previously unknown types of ketenes—stable element‐substituted acylketenes. Germanium‐substituted acylketenes are also formed; however, clear evidence of 1,4‐addition of germanium halides was not obtained. In the reaction between Ph2PCl and pivaloylethoxyacetylene, phosphorus (III) substituted acylketenes initially formed underwent rapid [3 + 3] cyclodimerization.
Preparation and properties of some stable captodative diphosphenes carrying the N‐(9‐fluorenyl)‐N‐mesitylamino group as an electron‐donating new sterically protecting auxiliary
Authors: Abe Masatoshi , Toyota Kozo , Yoshifuji Masaaki 
Published: January 2005

AbstractThe N‐(9‐fluorenyl)‐N‐mesitylamino group was utilized as an electron‐donating new sterically protecting group and thus several captodative 1‐amino‐2‐aryldiphosphenes were prepared. The push‐pull substituent effect on the ‐PP‐ bond was demonstrated by 31P NMR, and the reactivities of the captodative diphosphenes were studied.
Deoxygenation of nitro and nitrosoaromatics by photolysis with t‐BuHgl/Kl. Regiochemistry of tert‐Butyl radical addition to nitrosoaromatics [1]
Authors: Russell Glen A. , Yao Ching‐Fa 
Published: January 2005

AbstractPhotolysis of nitroaromatics in the presence of t‐BuHgI/KI in Me2SO or DMF leads to products formed by t‐Bu• addition to the nitroso compounds. Similar products are formed in the dark in the presence of K2S2O8. Nitroso or nitrobenzene is converted into N,O‐di‐tert‐butylphenylhydroxylamine by a process involving N‐tert‐butylphenylhydroxylamine as an intermediate. In the presence of PTSA and KI, N‐tert‐butylphenylhydroxylamine predominates in Me2SO, but in DMF, the phenylhydroxylamine is reduced to N‐tert‐butylaniline. In a similar fashion, o‐nitrosotoluene is converted into o‐MeC6H4N(Bu‐t)OBu‐t, o‐MeC6H4N(Bu‐t)OH, and o‐MeC6H4NHBu‐t. p‐Nitroso‐N,N‐dimethylaniline forms the N,O‐di‐tert‐butylated derivative in the absence of acid but in the presence of PTSA/KI yields p‐Me2NC6H4NHBu‐t. Excellent yields of the N,O‐di‐tert‐butylated arylhydroxylamines are formed in DMF from the nitroaromatics with para Me2N, OH, I, Br, Cl, and ortho Ph or PhNH substituents. Nitrobenzenes with p‐CHO, p‐PhCO, or p‐CN substituents are deoxygenated to the nitroso compounds which react with t‐Bu• to form the tert‐butoxyamino radicals (ArṄOBu‐t). In Me2SO, the amino radicals react to form ArN(HgI)OBu‐t compounds which condense with the nitroso compounds to yield the azoxy compounds. With the p‐CN substituent, the azoxy compound is subsequently deoxygenated and tert‐butylated to yield p‐NCC6H4N(Bu‐t)NHC6H4CN‐p. In the presence of PTSA/KI, the amino radicals are reduced to p‐Y‐ArNHOBu‐t (Y = PhCO, CN). The compounds Y‐ArN(Bu‐t)OBu‐t undergo photochemical degradation to yield Y‐ArNHBu‐t with Y = p‐PhCO or p‐CN in a reaction that is inhibited by I−. With PTSA/H2O/KI in Me2SO, p‐Me2NC6H4N(t‐Bu)OBu‐t is converted into 4‐(N‐tert‐butylimino)‐2,5‐cyclohexadien‐1‐one, p‐Me2NC6H4NHBu‐t, and p‐tert‐butylamino‐m‐tert‐butoxy‐N,N‐dimethylaniline. o‐MeC6H4N(Bu‐t)OH reacts with PTSA/KI to form o‐MeC6H4N(Bu‐t)H in DMF or a mixture of the aniline and 4‐(N‐tert‐butylimino)‐3‐methyl‐2,5‐cyclohexadien‐1‐one in Me2SO. In the absence of KI, only the cyclohexadienone is formed in Me2SO.
A new range of heterocyclic telluronium salts based on 1,2,4,5‐bis(telluracyclopentano)benzene: Synthesis and spectroscopic considerations
Authors: Al‐Shirayda Hatif A. 
Published: January 2005

AbstractThe reactions of 1,2,4,5‐tetrakis(bromomethyl)‐benzene with sodium organotellurates (NaTeR) afford white telluronium salts of the type XRTe(CH2)2C6H2(CH2)2TeRX where R = p‐EtOC6H4 and p‐MeOC6H4 and X = Br.Reactions of 1,2,4,5‐tetrakis(bromomethyl)‐benzene with elemental tellurium powder and an excess of sodium iodide in dimethyl sulfoxide (DMSO) give 1,2,4,5‐bis(1,1‐diiodotelluracyclopentano)benzene, C10H10Te2I4 as orange‐red crystals in poor yield, together with a yellow amorphous precipitate as the main product, the structure of which is still obscure.Reduction of the bis(diiodide) compound gave a light and air sensitive ditelluride, C10H10Te2, which, on treatment with ethyl bromide, afforded a white telluronium salt of 1,2,4,5‐bis(1′‐bromo‐1′‐ethyl‐telluracyclopentano)benzene, C14H20Te2Br2. The synthesis, spectroscopic data, and solution properties of the prepared compounds are reported and discussed.
Spectroscopic studies and X‐ray crystal structures of charge‐transfer complexes of 1,4,7‐trithiacyclononane with diiodine
Authors: Cristiani Franco , Devillanova Francesco A. , Isaia Francesco , Lippolis Vito , Verani Gaetano , Demartin Francesco 
Published: January 2005

Abstract1,4,7‐Trithiacyclononane ([9]aneS3) reacts with molecular diiodine in CH2Cl2 to form a 1:1 adduct. The formation constant and the thermodynamic parameters of this adduct have been determined by UV‐visible spectra of several solutions at the temperatures of 15, 20, 25, 30, and 35°C. The 13C NMR spectra show that adducts with higher ligand/diiodine molar ratios are formed. Two neutral charge‐transfer molecular compounds having formula 2[9]aneS3 · 4I2 (I) and [9]aneS3 · 3I2 · (II) have been obtained as crystals. The crystals of I are triclinic (a = 8.498(2) Å, b = 13.984(4) Å, c = 14.898(6) Å, α = 65.57(2)°, γ = 89.19(2)°, γ = 81.26(2)°, Z = 2, space group P1; R = 0.025) and contain units formed by two [9]aneS3 molecules connected by a diiodine molecule; one [9]aneS3 binds two other diiodine molecules, while the second binds only one other diiodine molecule. The crystals of II are monoclinic (a = 13.810(2) Å, b = 9.829(4) Å, c = 16.198(6) Å, β = 113.41(2)°, Z = 4, space group P21/c; R = 0.019) and contain molecules of [9]aneS3 binding three diiodine molecules. FT‐Raman spectra in the characteristic v(I–I) region, carried out on the solid adducts, are discussed in comparison with the structural parameters.
2‐Hydroperfluoropropyl azide—a versatile reagent for the oxidative fluorination of organic compounds of trivalent phosphorus
Authors: Lermontov Sergei A. , Sukhojenko Ivan I. , Popov Anatoli V. , Pushin Alexei N. , Martynov Ivan V. , Zefirov Nikolai S. , Stang Peter J. 
Published: January 2005

Abstract2‐Hydroperfluoropropyl azide CF3CHFCF2N3, 1, an inexpensive, readily available, and stable (easy to store) compound, is suggested as an effective fluorinating reagent for different classes of trivalent organophosphorus compounds in accordance with the general scheme R3P → R3PF2. Generally, the reactions are performed without solvent, the highly volatile CF3 CHFCN being the main by‐product. The fluorination is usually an exothermic process, but slight heating is necessary in the case of alkyldifluorophosphites. The unusual Arbuzov rearrangement, accompanied by isomerization of an isobutyl or neopentyl group into a tert‐group, ROPF2 → t‐R′POF2, under the action of a catalytic amount of 1, was observed.
Synthesis of saccharidyl N,N‐bis(2‐chloroethyl)phosphoramidates and their antitumor activity
Authors: Chen Ru‐Yu , Chen Xiao‐Ru 
Published: January 2005

AbstractIn order to search for novel antitumor drugs with high activity and low toxicity, a series of new compounds, galactopyranosyl (or glucofuranosyl) N,N‐bis(2‐chloroethyl) phosphoramidates, have been synthesized. The structures of all compounds prepared were proved by 1H NMR, 31P NMR, IR, and MS spectroscopy and by elemental analyses. The existence of diastereoisomers was detected by 31P NMR and 1H NMR spectra. One of the two isomers of 3a and also one of 4b, i.e., 3a′ and 4b′, respectively, were obtained by recrystallization. The absolute configurations of 3a′ and 4b′ were determined by single‐crystal X‐ray diffraction analysis. The results of the preliminary biological tests indicated that some of these compounds have certain inhibitory activities against L1210 cells.
Synthesis and reactions of phenyliodonium bis(perfluoroalkanesulfonyl) methides
Authors: Zhu Shi‐Zheng 
Published: January 2005

AbstractPhenyliodonium bis(perfluoroalkanesulfonyl) methides PhI+−C(SO2RF)2 (3) were prepared by the reaction of bis(perfluoroalkanesulfonyl)methanes with diacetoxyiodobenzene. The photochemical reactions of 3 with alkenes, methanol, bromine, and benzene gave the corresponding addition or insertion products. When 3 was irradiated in the presence of methyl sulfide, pyridine, and triphenylphosphine, it afforded the ylides containing the bis(perfluoroalkanesulfonyl)methylene functionality, Y+−C(SO2RF)2. In these reactions the bis(perfluoroalkanesulfonyl)carbene intermediate (RFSO2)2C: may be involved. Irradiation or heating of 3 in DMSO gave a 1 : 1 complex, the structure of which was confirmed by X‐ray diffraction analysis. Bis(perfluoroalkanesulfonyl)‐methylene dimethyloxosulfonium ylides Me2(O)S+−C(SO2RF)2 were obtained by air oxidation of bis(perfluoroalkanesulfonyl)methylene dimethylsulfonium ylides.
Cyclic sulfur nitrogen compounds and phosphorus reagents: Part XII. Reactions of S4N4 with (2‐pyridylamino) phosphines [1]
Authors: Mohan T. , Thomas C. J. , Rao M. N. Sudheendra , Aravamudan G. , Meetsma Auke , van de Grampel Johan C. 
Published: January 2005

AbstractTetrasulfurtetranitride, S4N4 reacts with (2‐pyridylamino)‐diphenylphosphine in MeCN at room temperature to form the cyclotrithiazene (NC5H4NH)‐Ph2PNS3N3 (1) in good yield. By contrast, the cyclophosphathiazenes Ph2PS2N3 (2) and 1,5(Ph2P)2S2N4 (3) are isolated from the same reaction mixture under reflux conditions. In solution, compound 1 is found to be transformed into 2. The reaction of S4N4 with (2‐pyridylamino)phenyl(dicyclohexylamino)phosphine in MeCN at room temperature affords Ph(DCA)PS2N3 (4) (DCA = dicylohexylamino) as the only reaction product. This on treatment with norbornadiene produces the addition product Ph(DCA)PS2N3·C7H8 ( 5 ).The structure of 4 has been established by X‐ray diffraction. Its PSN ring adopts a skew boat conformation with SN bond lengths varying from 1.574(4) to 1.606(4) Å. The mean value of the endocyclic PN bonds amounts to 1.618(3) Å.
Dialkynyl selenides: Synthesis, 13C NMR spectra, and molecular orbital calculations
Authors: Murai Toshiaki , Shimizu Atsushi , Tatematsu Shūji , Ōno Kazuhiko , Kanda Takahiro , Kato Shinzi 
Published: January 2005

AbstractReactions of SeCl4 with lithium bis(trimethylsilyl)amide and terminal acetylenes in the presence of BuLi or AIBN afforded the corresponding dialkynyl selenides in moderate to high yields. The reaction may proceed via a selenium amide 7 and an alkynyl selenium amide 8. The comparison of 13C NMR spectra of dialkynyl selenides and tellurides has disclosed that the differences of the chemical shift of acetylenic carbons between Se and Te derivatives are consistent regardless of their substitution patterns. Ab initio molecular orbital calculations are reported for dialkynyl ether and chalcogenides. The calculated structures, charge distributions, and orbital energies are discussed.
The B6H14 problem: Generation of a catalogue of conceivable isomers
Authors: Fontain Eric 
Published: January 2005

AbstractThe structure‐generating feature of the computer program RAIN (reactions and intermediates networks) was used to produce the complete set of 48 conceivable B6H14 isomers with twofold constitutional symmetry. The constitutional isomers are built from BH units and contain up to two closed BBB three‐center bonds.
UV‐visible, IR, and 13C NMR studies on CT complexes between some thiohydantoins and molecular diiodine
Authors: Cristiani Franco , Devillanova Francesco A. , Garau Alessandra , Isaia Francesco , Lippolis Vito , Verani Gaetano 
Published: January 2005

AbstractThe reaction of some 5,5‐dimethyl‐2‐thiohydantoin derivatives (X = O, S; R, R′ = H, Me) with molecular diiodine has been studied in CH2Cl2 solution by different spectroscopic techniques. The formation constants (K) of the 1 : 1 molecular adducts and their thermodynamic parameters have been measured by UV‐visible spectroscopy. The results allow us to point out the different donor properties of C(2) = S thioketonic sulfur between the two series of compounds (X = O, S) and the influence of N(1) and N(3) methylation on the K's. From the analysis of the ν(NH) frequencies, it has been possible to show hydrogen bond interactions between the NH's and the S‐bonded iodine; this seems to be an important factor in determining the K values.
New perthiophosphonic acid anhydrides and the direct indication of the dimer‐monomer equilibrium. NMR and X‐Ray Studies
Authors: Beckmann Haiko , Großmann Gisbert , Ohms Gisela , Sieler Joachim 
Published: January 2005

AbstractNew perthiophosphonic acid anhydrides (R‐PS2)n with R = 2,4,6‐tri‐iso‐propylphenyl and 2,4‐di‐tert‐butyl‐6‐methylphenyl have been prepared. For the latter case, the isolation of the monomer (n = 1), the 2,4‐di‐tertbutyl‐6‐methylphenyl‐dithioxophosphorane, and both dimers (n = 2), cis‐ and trans‐2,4‐bis(2,4‐di‐tertbutyl‐6‐methylphenyl)‐2, 4‐dithioxo‐1, 3, 2, 4‐dithiadiphosphetane, has been determined. The new cis and trans dithiadiphosphetanes and dithioxophosphoranes as well as the known compounds (2,4,6‐trimethylphenyl‐PS2)2 and 2,4,6‐tri‐tert‐butylphenyl‐PS2 are characterized by solution and high resolution solid‐state 31P and 13C NMR spectroscopy. The existence of a dimer‐monomer equilibrium is directly proved by 2D exchange 31P NMR spectroscopy. It is shown that the reaction of the monomer with methanol is faster than the reaction of the dimer with methanol.
Reactions of triethylgermylpentafluorobenzene with some electrophilic agents
Authors: Bardin Vadim V. , Rogoza Ljudmila N. , Furin Georgii G. 
Published: January 2005

AbstractTriethylgermylpentafluorobenzene C6F5GeEt3 reacts with CF3SO3H, HSO3Cl, Me3SiOSO2Cl, chlorine, bromine, Cl2/AlCl3, or Br2/AlBr3 with cleavage of the CarylGe bond. Cesium fluoride promotes electrophilic degermylation of C6F5GeEt3, possibly via the intermediate formation of a tetraorganylfluorogermanate.
Synthesis and rearrangement of triazinoquinazolines
Authors: Ibrahim Yehia A. , Elwahy Ahmed H. M. 
Published: January 2005

AbstractSelective syntheses of triazino[4,3‐a]quinazolines 3a–e and their isomeric triazino[3,2‐b]quinazolines 4a–e by cyclization of the appropriate α‐keto acid hydrazones 2a–e under different reaction conditions are described. The angular triazinoquinazolines 3a–e were readily rearranged to the corresponding linear isomers 4a–e when heated in acetic anhydride in the presence of sodium acetate. This rearrangement was proposed to proceed via the intermediate isomeric triazino[3,4‐b]quinazolines 5a–e. The N‐methyl derivative 10 (of the intermediate 5b) was prepared and rearranged to 11, which is the N‐methyl derivative of 4b.
The reaction of vicinal triketones with cumulative phosphorus ylides. Synthesis of phosphoranylidenecyclobutanes
Authors: Soliman Fouad M. , El‐Kateb Ahmed A. , Hennawy Ibtisam T. , Abdel‐Malek Hoda A. 
Published: January 2005

Abstract1,2,3‐Indantrione (1), diphenylpropanetrione(6), and alloxan (8) can be converted by reactions with ketenylidene‐(2a) and thioketenylidenetriphenylphosphorane (2b) into phosphoranylidenecyclobutanes (5, 7, and 9). The structures of the new cyclic compounds were confirmed on the basis of elemental analysis and spectral studies.
The synthesis and antitumor activity of novel 1,3,5,2‐trizaphosphorines linked with nitrogen mustards
Authors: Chen Ru‐Yu , Mao Li‐Juan 
Published: January 2005

AbstractA series of novel derivatives of 2,5‐dihydro‐1,3,5,2‐triazaphosphorine has been synthesized and the structures of the most stable tautomers have been confirmed by 1H NMR and IR spectroscopy, MS, elemental analyses, and quantum chemistry calculations. We suggest that the thioenol form is more stable than the thione form which has been thought to be more stable up to the present time. The bioassay tests indicated that most of the new products have good antitumor activity.
Macrocycles containing bicyclophosphorane moieties [1]
Authors: Houalla Douraid , Bounja Zouhair , Skouta Saïd , Wolf Robert , Jaud Joel 
Published: January 2005

AbstractThe first stable macrocycles, 12–15, 16, 18, and 23, containing pentacovalent phosphorus have been obtained by an Atherton–Todd reaction between the bis(hydridobicyclophosphoranes) 3–7 and the corresponding binucleophile HO(CH2)2X(CH2)2OH. The tricyclic monophosphoranes 8–11 as well as the noncyclic derivative 20 have also been isolated. A pathway that accounts for the formation of all these compounds is proposed. The X‐ray crystal study of two 16‐membered rings, 14, 15, confirms the diequatorial placement of the macrocyclic frame on the trigonal bipyramidal phosphorus which retains the most favorable axial‐equatorial‐axial annelation of the bicyclic moiety. Comparison of these two molecular structures points out the effect of the nature of X on the conformation of the macrocycle.
Studies of silicon–nitrogen ring formation from tetrachlorodisilanes
Authors: Shibley John L. , West Robert , Powell Douglas R. , Tessier Claire A. 
Published: January 2005

AbstractThe addition of n equiv of MesNHLi (n = 1, 2, 3, 4) and m equiv of 12‐crown‐4 (m = 0.1, 1, 2, 3, 4) to (RsiCl2)2 (R = Mesityl; t‐Butyl) in THF at −78°C resulted in higher yields and improved selectivities of cyclodisilazanes and azadisilacyclopropanes. The reaction of 2 equiv of MesNDLi with (MesSiCl2)2 (I) yielded cis‐2‐chloro‐1,2,3,4‐tetramestylcyclodisilazane (2a) with 95% SiH deuteration. 2a was quantitatively chlorinated with retention of stereochemistry by N‐chlorosuccinimide to give the cis dichlorocyclodisilazane (3). Variable‐temperature 1H NMR studies from −70°C to 25°C in d8‐THF were performed on 1, 2a, 2b, and 3. 1 exhibited little variation throughout the temperature range, whereas 2a, 2b, and 3 showed several rotational isomers. trans‐2,3‐Bis(mesitylamino)‐1,2,3‐trimesitylazadisilacyclopropane was shown to isomerize to the cis isomer in the presence of n‐BuLi or MesNHLi. The molecular structures of 1 and 3 were determined by X‐ray crystallography. Compound 1 crystallized in the monoclinic space group P21/c, with cell parameters a = 16.599(2) Å b = 14.633(2) Å, c = 16.945(2) Å, β = 92.044(13)°, V = 4113.1(8) Å3, Z = 8, d (calcd) = 1.409 g/cm3, and R = 6.88%. Compound 3 ° C6H6 crystallized in the orthorhombic space group Pbca, with cell parameters a = 17.906(4) Å, b = 13.918(3) Å, c = 31.700(6) Å, V = 7900(3) Å3, Z = 8, d (calcd) = 1.194 g/cm3, and R = 7.52%.