Enantioselective synthesis of cyclobutanes via sequential Rh-catalyzed bicyclobutanation/Cu-catalyzed homoconjugate addition.

Journal of the American Chemical Society

PubMedID: 23758288

Panish R, Chintala SR, Boruta DT, Fang Y, Taylor MT, Fox JM. Enantioselective synthesis of cyclobutanes via sequential Rh-catalyzed bicyclobutanation/Cu-catalyzed homoconjugate addition. J Am Chem Soc. 2013;135(25):9283-6.
Enantiomerically enriched cyclobutanes are constructed by a three-component process in which t-butyl (E)-2-diazo-5-arylpent-4-enoates are treated with Rh2(S-NTTL)4 to provide enantiomerically enriched bicyclobutanes, which can subsequently engage in homoconjugate addition/enolate trapping sequence to give densely functionalized cyclobutanes with high diastereoselectivity. This three-component, two-catalyst procedure can be carried out in a single flask. Rh2(S-NTTL)4-catalyzed reaction of t-butyl (Z)-2-diazo-5-phenylpent-4-enoate gives the B├╝chner cyclization product in excellent enantioselectivity.