Nickel-catalyzed reductive carboxylation of styrenes using CO2.

A nickel-catalyzed reductive carboxylation of styrenes using CO2 has been developed. The reaction proceeds under mild conditions using diethylzinc as the reductant. Preliminary data suggests the mechanism involves two discrete nickel-mediated catalytic cycles, the first involving a catalyzed hydrozincation of the alkene followed by a second, slower nickel-catalyzed carboxylation of the in situ formed organozinc reagent. Importantly, the catalyst system is very robust and will fixate CO2 in good yield even if exposed to only an equimolar amount introduced into the headspace above the reaction.

Reactivity studies of 3,3-bis(trimethylsilyl)-2-methyl-1-propene in Lewis acid-catalyzed allylation reactions.

Allylation reagents, which possess geminal bis-trimethylsilyl substitution, are readily prepared from E- or Z-alkenyl bromides. The reactivity of 3,3-bis(trimethylsilyl)-2-methyl-1-propene (1) is described and predominantly provides ene reactions with aldehydes to give alcohol 2 in the presence of BF3.OEt2. Alternatively, Sakurai allylation reactions of 1 are observed by using stronger Lewis acids in methylene chloride to exclusively yield E-trisubstituted alkenylsilanes 3.