η3-pyranyl and η3-pyridinyl molybdenum π-complexes as chiral scaffolds for the enantioselective construction of substituted oxa- and aza[3.3.1]bicyclics:: First enantio- and regiocontrolled [5+3] cycloaddition reactions

The first Mo-mediated [5+3] cycloadditions are reported. 3-Substituted pyranyl and pyridinyl molybdenum π-complexes participate in enantiocontrolled [5+3] cycloadditions and provide a new and efficient synthetic approach to oxa- and aza[3.3.1]bicyclics of high enantiomeric purity. The reaction proceeds in good to excellent yields and with complete regio- and endo-selectivities; it diverts to a [2+3] cycloaddition pathway when 2-substituted heterocycle π-complexes are used. This methodology, coupled with a variety of general demetalation protocols, holds much promise in synthetic applications. Copyright © 2003 American Chemical Society.