Steven C. Vick

Organolithium routes to 1,2-disubstituted ethylene derivatives. An attempted synthesis of 1,2-dilithioethylene

Abstract The attempted preparation of trans -1,2-dilithioethylene by the action of two molar equivalents of n-butyllithium on trans -1,2-bis(tri-n-butystannyl) ethylene was unsuccessful, the reaction stopping at the Bu 3 SnCHCHLi + BuLi stage. However, trans -1,2-disubstituted ethylene derivatives could be prepared in good yield by a stepwise sequence in a one-pot process. Thus, trans -Bu 3 SnCHCHSnBu 3 was treated successively with molar equivalents of n-Buli, Me 3 SiCl n-Buli and Me 2 CO to give trans -Me 3 SiCHCHCMe 2 OH in 63% yield. Prepared in similar fashion were trans -Me 3 SiCHCHSiMe 3 trans -Me 3 SiCHCHSnMe 3 and trans -Me 3 SiCHCHCH 3 . These products, as well as ( trans -Me 3 SiCHCH) 2 Hg, also were prepared by appropriate reactions of trans -Me 3 SiCHCHLi, which was obtained by the transmetalation reaction of phenyllithium with trans -Me 3 SiCHCHSnPh 3 in diethyl ether solution. The (Ph 3 P) 4 Pd-catalyzed demercuration of trans -Me 3 SiCHCH) 2 Hg gave trans , trans -Me 3 SiCHCHCHCHSiMe 3 in 95% yield.

Synthesis of 1,8-bis(trimethylsilyl)- and 1,8-bis(trimethylstannyl)-naphthalene. The relative steric effects of carbon, silicon and tin in the 1,8-bis(trimethylelement)-naphthalenes

Abstract 1,8-Bis(trimethylsilyl)- and 1,8-bis(trimethylstannyl)-naphthalene have been prepared by reaction of 1,8-dilithionaphthalene with trimethylchlorosilane and trimethyltin chloride. The steric effects of these Me3M substituents in these compounds were evaluated by means of NMR spectroscopy. Acids and carbon tetrachloride were found to catalyze the rearrangement of 1,8-bis(trimethylsilyl)naphthalene to the 1,7-isomer.

Hexamethylsilirane : I. Preparation, characterization and thermal decomposition

Abstract Hexamethylsilirane has been prepared by the action of magnesium on dimethyl-bis(α-bromoisopropyl)silane in tetrahydrofuran (THF) solution. It was found to be highly reactive toward atmospheric oxygen and moisture and to decompose when heated in solution at 60–75°C. Its decomposition results in the extrusion of dimethylsilylene which may add to the tetramethylethylene produced in the decomposition to regenerate the silirane, insert into the reactive SiC2 ring of the silirane to give octamethyl-1,2-disilacyclobutane or oligomerize to give (Me2Si)n oils. Dimethyldiisopropyl-, tetraisopropyl- and tert-butyltriisopropylsilane were prepared by catalytic hydrogenation of the corresponding isopropenylsilanes. Bromination of dimethyldiisopropylsilane at 65°C resulted in exclusive formation of dimethyl-bis(α-bromoisopropyl)silane.

Silacyclopropenes: I. Synthesis and properties of some silacyclopropenes

Abstract The thermal decomposition of hexamethylsilirane in the presence of selected disubstituted acetylenes (Me3SiCCSiMe3), Me2HSiCCSiMe2H, Me3SiCCCH3, Me3SiCCCMe3, Me3CCCCH3) resulted in Me2Si addition to the CC bonds to give the respective silacyclopropenes. These are thermally stable but are extremely reactive toward atmospheric oxygen and moisture and react readily with methanol and ethanol at room temperature with SiC (ring) bond cleavage. The very high field 29Si NMR resonance (−87 to −106 ppm) is a characteristic feature of the silacyclopropene ring.

The preparation of a 1,2-disilacyclobutane and a 1,2-disilacyclobut-3-ene by dimethylsilylene insertion into the silacyclopropane and silacyclopropene ring systems. New silacyclopropenes

Abstract The thermolysis of hexamethylsilacyclopropane in the presence of 1,1-dimethyl-2,3-bis(trimethylsilyl)-1-silacyclopropene resulted in formation of octamethyl-1,2-disilacyclobutane and 1,1,2,2-tetramethyl-3,4-bis(trimethylsilyl)-1,2-disilacyclobut-3-ene via Me 2 Si insertion into the silacyclopropane and silacyclopropene rings. Thermolysis of hexamethylsilacyclopropane alone in benzene at 70° gave the former compound in 40% yield. Oxidation of these compounds with O 2 gave the respective 1,3-disila-2-oxa-cyclopentane and 1,3-disila-2-oxa-cyclopent-4-ene compounds. Four new silacyclopropenes (VIIIa–d) have been prepared and characterized.

Novel two atom insertions into the silacyclopropane and silacyclopropene rings

Abstract The reactions of hexamethylsilirane and 1,1-dimethyl-2,3-bis(trimethylsilyl)-1-silirene with aromatic and α,β-unsaturated aldehydes and ketones gave insertion products having the 1-sila-2-oxacyclopentane and 1-sila-2-oxacyclopent-4-ene structures, respectively. Benzaldehyde methylimine reacted with hexamethylsilirane in similar fashion, giving 1,1,2,4,4,5,5-heptamethyl-3-phenyl-1-sila-2-azacyclopentane. Reactions of the silirane and silirene with phenylacetylene gave both ring insertion and ring opening products. 1,1-Dimethyl-3,4-diphenyl-1-silacyclopentadiene was formed in the reaction of the silirene with an excess of phenylacetylene in the presence of a catalytic quantity of bis(triphenylphosphine)palladium dichloride.

Two atom insertions into the silacyclopropane and silacyclopropene rings: mechanistic considerations

Abstract Novel two atom insertion reactions into the SiC2 rings of hexamethylsilirane and 1,1-dimethyl-2,3-bis(trimethylsilyl)-1-silirene involving the C bonds of styrene and α-methylstyrene, 1,3-butadiene and its 2-methyl and 2,3-dimethyl derivatives, and, in the presence of ultraviolet radiation, of aliphatic aldehydes and ketones, are reported. A radical mechanism is suggested tobe operative in these reactions. Also described are novel palladium-catalyzed reactions of the silirene with terminal and internal acetylenes.

Unusual lithium transfer reactions in lithium-substituted organo-silicon compounds. Reinvestigation of the reaction of 1,8-di-lithionaphthalene with trimethylchlorosilane

Abstract The product of the reaction of 1,8-dilithionaphthalene with trimethylchlorosilane is 2-(1-naphthyl)-2,4,4-trimethyl-2,4-disilapentane rather than 1,8-bis(trimethylsilyl)naphthalene as previously reported. A novel, presumably intramolecular, metalation process transfers the organolithium function in 1-trimethylsilyl-8-lithionaphthalene to a methyl substituent on the trimethylsilyl group, and it is this new organolithium reagent which reacts with the second mole of trimethylchlorosilane. Ring-opening of 1,1-dimethyl-2,3-bis(trimethylsilyl)-1-silirene by methyllithium is followed by a similar transfer of the organolithium function from the vinylic carbon atom to a methyl group on silicon.

The Synthesis of Dimethyl(iodomethyl)tin Iodide and 1, 1, 3, 3, 5, 5-Hexamethyl-1, 3, 5-tristannacyclohexane

Abstract The synthesis of dimethyl(iodomethyl)tin iodide by treatment of dimethyltin dichloride with iodomethylzinc iodide is described. This represents an improvement over the diazomethane route.1 Treatment of the iodide with magnesium metal yields 1, 1, 3, 3, 5, 5-hexamethyl-1, 3, - 5-tristannacyclohexane.

An organolithium route to substituted η4-cyclobutadienecobalt complexes

Abstract The reaction of η 5 -cyclopentadienyl-η 4 -1,3-bis(triphenylstannyl)-2,4-diphenylcyclobutadienecobalt with phenyllithium in tetrahydrofuran gave an organolithium reagent in which one Ph 3 Sn substituent was replaced by lithium. Reaction of this reagent with trimethylchlorosilane gave the expected trimethylsilyl derivative. The Ph 3 Sn group in this product could be replaced by lithium in a second reaction with phenyllithium, but a dilithio derivative could not be prepared directly from the bis(triphenylstanyl) compound in a single step.