N-Substituted tertiary and O-substituted quaternary carbon stereogenic centers by site-, diastereo- and enantioselective vinylogous Mannich reactions

作者：Silverio Daniel L; Fu Peng; Carswell Emma L; Snapper Marc L; Hoveyda Amir H^*

来源：Tetrahedron Letters, 2015, 56(23): 3489-3493.

DOI：10.1016/j.tetlet.2015.04.006

• Catalysis
• Enantioselective synthesis
• Quaternary carbons
• Siloxyfurans
• Silver complexes
• Vinylogous Mannich reactions

A readily accessible small-molecule phosphine, derived from commercially available starting materials such as an enantiomerically pure amino acid, serves as the precursor to a Ag-based chiral complex that can be prepared and used in situ to promote a variety of enantioselective vinylogous Mannich (EVM) reactions that involve siloxypyrroles as reaction partners. Transformations with unsubstituted nucleophilic components proceed efficiently and with exceptional site- (gamma vs alpha-addition), diastereo- and enantioselectivity [up to 98% yield, generally >98:2 gamma/alpha and diastereomeric ratio (dr) and up to 99:1 enantiomeric ratio (er)]. The first examples of efficient, diastereo- and enantioselective vinylogous Mannich additions with 5-methyl-substituted siloxyfuran, resulting in the formation of O-substituted quaternary carbon stereogenic centers are presented as well. Appreciable efficiency and diastereo- and enantioselectivity (up to >98:2 dr and >99:1 er) is accompanied by formation of a-addition products that can be oxidatively removed.

• 出版日期2015-6-3