In(I)OTf has been uncovered as an effective Lewis acid catalyst for unprecedented nucleophilic substitution of acetals or ketals with allylboronates. A transmetalative S(N)1 mechanism is proposed in which a single In(I) center acts as a dual catalyst to activate both reagents sequentially. Contrary to the classic gamma-selectivity of allylsilanes (Hosomi-Sakurai reaction), this In(I)-catalyzed borono variant displays distinct alpha-selectivity. Substrate scope and functional group tolerance proved to be excellent.
Department of Chemistry, School of Science and Graduate School of Pharmaceutical Sciences, The University of Tokyo, The HFRE Division, ERATO, JST, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
