Zinc Compounds Diphenylzinc

Later the same group demonstrated that the use of dialkyl- or diaryl-zinc compounds in dichloromethane enables a tertiary chlorine atom to be replaced by groups other than methyl. For example, the reaction of trityl chloride with diphenylzinc constitutes the best current synthesis of tetraphenylmethane (54% isolated yield). 

Despite the extensive history of organozinc chemistry, the first solid-state structure of a Lewis base-free diorganozinc compound with cr-bound ligands, namely diphenylzinc, was not reported until 1990.37 Diphenylzinc was synthesized by the transmetallation of diphenylmercury with metallic zinc (Scheme 10) and, after multiple sublimations, obtained halide free in 67% yield. 

In general, simple dialkylzinc and diarylzinc compounds are monomers in which the zinc atom, as a consequence of its ground-state electronic configuration, is sp hybridized. Thus, such molecules contain a linear C—Zn—C arrangement. The only known exception to this rule is diphenylzinc, which in the solid state is a dimer formed via electron-deficient /r -bridging phenyl groups. 

Compared with asymmetric ethylation, reports on asymmetric phenylation are limited. We disclosed the enantioselective phenylation using diphenylzinc prepared in situ from phenyl Grignard reagent and zinc chloride. This method needs a stoichiometric amount of chiral amino alcohol DBNE 18 but good ee of 82% was achieved [32], A catalytic phenylation was examined using planar chiral compound 1 based on ferrocene, and chiral diaryl carbinols of moderate ee were provided from diphenylzinc and 4-chlorobenzaldehyde (Scheme 10) [33]. A catalytic and highly enantioselective phenylation was realized by binaphthyl-based chiral catalyst 23. In this reaction, the addition of 2 equivalents of diethyl-zinc against catalyst increases the yield and ee [34]. Recently, chiral amino alcohol DPMPM 9 was also reported to be an efficient catalyst for asymmetric phenylation [35]. 

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