Regioselective Palladium-Catalyzed Alkylation of Allylic Halides with Benzylic Grignard Reagents. Two-Step Synthesis of Abietane Terpenes and Tetracyclic Polyprenoid Compounds
作者:Viale Rosales、Jorge L. Zambrano、Martin Demuth
DOI:10.1021/jo010786z
日期:2002.2.1
A highly regioselective palladium-catalyzed alpha-alkylation of allylic bromides 1a,c-e and chloride 1b with substituted and unsubstituted benzylic Grignard reagents is reported. The resulting all-trans polyenehomobenzene derivatives were obtained in excellent yields and regioselectivity. These products were easily converted to abietane-type diterpenes (10-12) and tetracyclic polyprenoid compounds
Highly Enantioselective Proton-Initiated Polycyclization of Polyenes
作者:Karavadhi Surendra、E. J. Corey
DOI:10.1021/ja305851h
日期:2012.7.25
This report describes the synthesis of a range of chiral polycyclic molecules (tricyclic to pentacyclic) from achiral polyene precursors by enantio-selective proton-initiated polycyclization promoted by the 11 complex of o,o'-dichloro-BINOL and SbCl5. Excellent yields (ca. 90% per ring formed) and enantioselectivety (20:1 to 50:1) were obtained. The process is practical as well as efficient, because the chiral ligand is both readily prepared from R,R- or S,S-BINOL and easily recovered from the reaction mixture by extraction.