A lactam-derived vinyl boronate as a stable and crystalline reagent for the synthesis of 2-substituted piperidines by Pd-catalyzed coupling reactions
摘要:
A delta-valerolactam-derived vinyl triflate has been converted into the corresponding vinyl boronate by Pd-catalyzed coupling with bis(pinacolato)diboron, which results in all umpolung. This boronate efficiently couples under Pd catalysis with aryl and heteroaryl bromides to give the corresponding 2-substituted piperidines ill excellent yields. (C) 2004 Elsevier Ltd. All rights reserved.
Acylboranes are among the most elusive boron-containing organic functional groups, a fact that has impeded development of new reactions employing them as substrates. A new synthesis of acyltrifluoroborates from benzotriazole (Bt)-based N,O-acetals has been developed. Two other routes provide acyltrifluoroborates containing alcohols, aldehydes, and carbamates. The ketone-like reactivity of the acyltrifluoroborate functional group is demonstrated, and the first X-ray structure of an acyltrifluoroborate is reported.