27962-40-9Relevant articles and documents
Clemmensen reduction. XII The synthesis and acidolysis of some diaryl-substituted cyclopropane-1,2-diols. The possible involvement of a cyclopropyl cation
Davis, Brian R.,Hinds, Mark G.
, p. 309 - 319 (2007/10/03)
The generation of a number of 1,2-diarylcyclopropane-1,2-diols is reported. Reaction of these in situ with acid gives, primarily, an α,β-unsaturated ketone in which the aryl substituent attached to the double bond is that which is best able to stabilize a benzylic cation. It is proposed that the reaction proceeds by O-protonation of the cyclopropane- 1,2-diol, followed by loss of water and opening of the resulting cyclopropyl cation and final deprotonation. Such initial O-protonation contrasts with the C-protonation normally observed in the acidolysis of cyclopropanols and other dialkyl- and alkylaryl-cyclopropane-1,2-diols.
The Reaction of Benzil with Grignard Reagents
Holm, T.
, p. 278 - 284 (2007/10/02)
Benzil reacts with Grignard reagents forming, in the first step, the 1,2-addition product (C-alkylation), but often also the 1,4-addition product (O-alkylation) and the reduction product, benzoin.The product distribution has been determined for mechanistic purposes for 16 Grignard reagents using a standard procedure.These results, and observations made using deuteriated reagents and the 5-hexenyl radical probe indicate an electron transfer (ET) mechanism for reagents having hydrogen in the β-position, while a polar mechanism is the most efficient for methyl, phenyl, benzyl and allyl Grignard reagents in the ether solution.For the ET mechanism, a six-centre transition state is suggested.Furthermore, a distinction is made between the primary cage product (O-alkyl) resulting from immediate combination of the radical pair, and the secondary cage product (C-alkyl) formed in the cage after rearrangement. 5-Hexenylmagnesium bromide yields uncyclised primary and secondary cage product, but also significant amounts of cyclised C-alkylation product formed by escape of the radicals from the cage and re-encounter after cyclisation of 5-hexenyl to cyclopentylmethyl.A recently suggested mechanism based on the existence of stable radical ion pairs is found to be unacceptable.
