Highly Stereoselective Synthesis and Hydrogenation of (<i>Z</i>)-1-Alkyl-2-arylvinyl Acetates: a Wide Scope Procedure for the Preparation of Chiral Homobenzylic Esters

Abstract

A synthesis of (Z)-1-alkyl-2-arylvinyl acetates 3&#13;\nwith broad scope is reported by using two complementary&#13;\nmethods. The first one uses a stereospecific gold-catalyzed&#13;\naddition of acetic acid to 1-iodo-alkynes, followed by a Suzuki&#13;\ncoupling. By the second, 1-methyl-2-arylvinyl substrates have&#13;\nbeen obtained selectively as the Z isomers by O-acylation of&#13;\nenolates of methyl benzyl ketones. In addition, the asymmetric&#13;\nhydrogenation of enol esters 3 has been covered for the first&#13;\ntime. Using rhodium catalysts based on chiral phosphinephosphite&#13;\nligands (P-OP), highly enantioselective hydrogenations&#13;\n(up to 99% ee) have been achieved for a wide range of substrates. Thus, the synthesis and enantioselective&#13;\nhydrogenation of 3 provides a convenient and versatile procedure for the synthesis of valuable chiral homobenzylic esters