ChemInform Abstract: REACTION OF 2,2‐DISUBSTITUTED 1‐(DIBROMOMETHYLENE)CYCLOPROPANES WITH METHYLLITHIUM

Abstract

Die Darstellung der Titelverbindungen (VI) wird beschrieben.

Three-Membered-Ring-Based Molecular Architectures

“…Reactions of propargylic alcohols with chlorodiarylphosphines in the presence of organic bases yield phosphorylpropadienes . Dibromocarbene addition to the phosphorylpropadiene 581 , prepared along this route, regioselectively furnished the adduct 582 , which could be subjected to the Doering−Moore−Skattebøl rearrangement to afford butatriene 583 (Scheme ). , The thermally unstable parent compound 584 had been obtained previously by Kostikov et al by treatment of the corresponding dibromocyclopropane obtained from 1,1-dicyclopropylpropadiene ( 567 ) with methyllithium 97 …”

Synthesis of Methylene- and Alkylidenecyclopropane Derivatives

“…The cyclopropanation of allene itself gives poor results, [40][41][42] but the addition of dichloro-or dibromocarbene generated in several ways (base-induced elimination from CHX 3 or trihaloacetate, thermal decomposition of phenyl(trihalomethyl)mercury or trichloromethyltrifluorosilane) to 1,1-disubstituted allenes afforded MCPs 44 in high yields (Scheme 10). 17,36,37,39,[43][44][45][46][47][48][49][50] The addition occurs selectively at the substituted double bond, providing that the reaction is carried out at moderate temperatures. At higher temperatures, different ACPs can be detected, as a result of a rearrangement via TMM species (see section IV.E).…”

“…Aryl substituents facilitate the isomerization and easily rearrange under the reaction conditions. 47 For example, 1,1-dichloro-2-methylene-3-phenylcyclopropane (45) derived by addition of dichlorocarbene to phenylallene rearranges to 46 at 60 °C (Scheme 11). 51 Contrary to phenylallene, alkyl monosubstituted allenes gave mixtures of cyclopropanation products at the substituted and unsubstituted double bonds, with the former prevailing (from 2:1 to 3:1).…”

“…The cyclopropanation of allene itself gives poor results, − but the addition of dichloro- or dibromocarbene generated in several ways (base-induced elimination from CHX 3 or trihaloacetate, thermal decomposition of phenyl(trihalomethyl)mercury or trichloromethyltrifluorosilane) to 1,1-disubstituted allenes afforded MCPs 44 in high yields (Scheme ). ,,,,−

10

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“…The temperatures required for this transformation are usually high, but they depend on the substituents. Aryl substituents facilitate the isomerization and easily rearrange under the reaction conditions )…”