Synthesis of Substituted Oxa- and Aza[3.2.1] and [4.3.1]Bicyclics via an Unprecedented Molybdenum-Mediated 1,5-“Michael-Type” Reaction

The direct internal nucleophilic functionalization of a pi-bound carbon of neutral TpMo(CO)2(5-oxo-eta3-pyranyl) and TpMo(CO)2(5-oxo-eta3-pyridinyl) complexes by enolates represents a new reaction profile for neutral TpMo(CO)2(eta3-allyl) complexes. This Mo-mediated "1,5-Michael reaction" proceeds in good to excellent yields and provides, after demetalation, a new and efficient synthetic approach to oxa- and aza[3.2.1]bicyclics of high enantiomeric purity.