Mechanism of Reduction of Diphenylacetylene by Metallic Lithium

Abstract

A zero-order reaction converts cis-dilithiostilbene (1), formed upon reduction of diphenylacetylene by lithium, into the trans isomer 2. The cis-monolithiated adduct acts as a catalyst.

Non-Deprotonating Methodologies for Organolithium Reagents Starting from Non-Halogenated Materials. Part 2: Transmetallation and Addition to Multiple Bonds

“…Additionally, the acenaphthylene 237 was also reduced by lithium in the presence of 4,4'-di-tert-butylbiphenyl (DTBB) producing the corresponding dianion, which was subsequently treated with different carbonylic compounds yielding the expected trans-1,2-disubstituted derivatives 238 (Scheme 62) [147]. The mechanism of the reduction of diphenylacetylene with lithium was discussed, showing that (Z)-1,2-dilithio-1,2-diphenylethene was formed as the most stable isomer, what is in sharp contrast with the trans preference for aliphatic dilithioethenes [148]. Maercker and co-workers described the preparation of the 3,4-dilithio-2,5-dimethylhexa-2,4-diene 240 by reduction of the 2,5-dimethylhexa-2,3,4-triene 239 with lithium metal, and the subsequent reaction with different electrophiles [149].…”

Organodilithium Intermediates as Useful Dianionic Synthons: Recent Advances

“…However, these compounds are not reactive enough for promoting reactions as Lewis acid catalysts. For this reason, and in order to improve the acidity of these bimetallic compounds, the bis-trimethylstannyl derivative 111 (R3M = Me3Sn) was treated with 6 equivalents of SnCl4 to give (R)-2,2'-bis(dichloromethylstannyl)-1,1'-binaphthyl (112), which shows promising catalytic properties and can be considered as the first chiral bis-metallic binaphthyl catalyst (Scheme 27) [61]. Clayden and co-workers reported recently a resolution of racemic 2,2'-dilithio-1,1'-binaphthyl (110) by reacting it with (-)-menthyl p-methylbenzene sulfinate, giving a mixture of two atropodiastereoisomeric sulfoxides, which can be separated by chromatography or crystallization [62].…”

“…The addition of MeOH at the same temperature yielded pure cis-stilbene as the only product (235; X = H), whereas cis-PhCD=CDPh (235; X = D) is formed on addition of MeOD. Since the reduction takes place on the surface of the metal, the addition of a second lithium atom is favored over any other outcome to give the dilithium aduct 234 (Scheme 53) [112].…”

Recent developments in homobimetallic reagents and catalysts for organic synthesis

“…Diphenylacetylene can be reduced by metallic lithium to form the cis-dilithium adduct 7, which was converted into cis-stilbene after treatment with methanol [11]. It has been found that trimethylsilyl substituted styrenes can also be reduced by metallic lithium to form the corresponding 1,2-dilithio intermediate 8 (Scheme 4) [12].…”