Magnesium bromide-promoted addition of heterosubstituted methylketene silyl acetals to alkoxy aldehydes. Diastereoselective synthesis of 3,4-syn-2-methylene- and 2-(alkoxymethyl)-3-hydroxy-4-alkoxy esters
Magnesium bromide-promoted addition of heterosubstituted methylketene silyl acetals to alkoxy aldehydes. Diastereoselective synthesis of 3,4-syn-2-methylene- and 2-(alkoxymethyl)-3-hydroxy-4-alkoxy esters
Asymmetric Cycloadditions of <i>o</i>-Quinone Methides Employing Chiral Ammonium Fluoride Precatalysts
作者:Ethan Alden-Danforth、Michael T. Scerba、Thomas Lectka
DOI:10.1021/ol802029e
日期:2008.11.6
The catalytic, enantioselective, [4 + 2] cycloaddition reaction of ortho-quinone methides with silyl ketene acetals is described. This mechanistically interesting reaction, initiated by a chiral cinchona alkaloid-derived ammonium fluoride "precatalyst" complex, affords a variety of alkyl- and aryl-substituted 3,4-dihydrocoumarin products in excellent yield and with good enantioselectivity.