Theodore F. Jula

The preparation of organolithium reagents by the transmetalation reaction: XI. Crotyllithium

Abstract Both cis - and trans -crotyltrimethyltin react with n-butyl- and methyllithium in ether to give crotyllithium in high yield. In each case, reaction of the reagent solution with trimethylchlorosilane gives an approximately 3 2 mixture of trans - and cis -crotyltrimethylsilane. These transmetalation equilibria permit the isomerization of cis - and trans -crotyltrimethyltin to a 3 2 trans / cis mixture by small amounts of n-butyl- or methyllithium. Metallic lithium also causes isomerization of the cis - and trans -crotyllithium isomers via a metal displacement process which generates a small amount of crotyllithium which is capable of exchanging crotyl groups with unconverted crotyltrimethyltin. The possible mechanism of the isomerization reactions observed is discussed.

The preparation of group IV organometallic compounds containing gem-dihalocyclopropyl groups

Abstract Seventeen new gem -dihalocyclopropyl-substituted derivatives of carbon, silicon, germanium and tin have been prepared by the Doering-Hoffmann or the phenyl(trihalomethyl)mercurial procedures from allylic and vinylic compounds of these elements. The reaction of vinyltrimethyltin with phenyl(bromodichloromethyl)mercury (to give 2,2-dichlorocyclopropyltrimethyltin) was complicated by a side reaction in which the phenylmercuric bromide formed cleaved the vinyl group from tin. The H 2 PtCl 6 -catalyzed addition trichlorosilane to 1,1-dichloro-2-vinylcyclopropane gave the expected 1,1-dichloro-2-(β-trichlorosilylethyl)cyclopropane, but thermal addition of trimethyltin hydride to this olefin apparently proceeded via a radical chain mechanism to give the ring-opened product. Me 3 SnCH 2 CHCHCH 2 -CCl 2 H.

Halomethyl-metal compounds : XXVIII. Phenyl(dibromochloromethyl)mercury as a bromochlorocarbene source☆

Abstract A number of gem-bromochlorocyclopropanes has been prepared by the reaction of PhHgCClBr2-derived bromochlorocarbene with olefins (cyclohexene, cyclooctene, 1-heptene, tetramethylethylene, cis- and trans-2-butene, styrene, acrylonitrile, vinyl acetate, allyltrimethylsilane, vinyltrimethylsilane, cis- and trans-1,2-dichloroethylene). Reaction of phenyl(dibromochloromethyl)mercury with 2,5-dihydrofuran gave an equimolar amount of the expected CC addition product and the CH insertion product, 2-(bromochloromethyl)-2,5-dihydrofuran. Similar CH insertion was observed with tetrahydrofuran. With cumene CClBr insertion occurred exclusively into the benzylic position.

Trimethylhalosilane elimination from trimethylsilylsubstituted gem-dihalocyclopropanes

Abstract The aluminum halide-catalyzed elimination of trimethylhalosilane from 1,1-dihalo-2-(trimethylsilyl)cyclopropanes (XCl and Br) resulted in the formation of propargyl halides, HCCCH2X. Reaction of 1,1-dichloro-2,2-dimethyl-3-(trimethylsilyl) cyclopropane with sodium ethoxide in ethanol also resulted in elimination of trimethylchlorosilane; the organic product was 3-ethoxy-3-methyl-1-butyne, HCCCMe2OEt, and a mechanism involving β-elimination of trimethylchlorosilane to give 1-chloro-3,3-dimethylcyclopropene and reaction of the latter to produce the acetylenic ether is suggested.