Intramolecular hydroboration of unsaturated phosphine boranes.
Homoallylic phosphine boranes undergo intramolecular hydroboration upon activation by triflic acid. The reaction occurs via an intermediate B-trifluorosulfonyloxyborane complex such as 15, followed by S(N)1-like or S(N)2-like displacement of the triflate leaving group, apparently leading to the formation of a four-center transition state. In the case of trisubstituted double bonds, as in the substrates 29 and 32, ionic hydrogenation of the alkene competes with internal hydroboration.
Shapland
Peter
P
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Vedejs
Edwin
E