Copper-Catalyzed Asymmetric Alkylation of β-Keto Esters with Xanthydrols

The copper(II) triflate-tert-butyl-bisoxazoline [Cu(OTf)2-t-Bu-BOX]-catalyzed asymmetric alkylation of β-keto esters using free benzylic alcohols such as xanthydrols, as alkylating agents, is herein described for the first time. This green protocol renders in general the corresponding products with good results in terms of both yields and enantioselectivities using different keto esters, even when quaternary stereocenters were created. The scope, limitations and mechanistic aspects of the process are also discussed.

Spanish Ministerio de Ciencia e Innovación (MICINN) (projects CTQ2010-20387 and Consolider Ingenio 2010, CSD2007-00006), FEDER, the Generalitat Valenciana (PROMETEO 2009/039) and the University of Alicante are gratefully acknowledged for financial support. A. B. would also like to thank MICINN for a Juan de la Cierva contract (JCI-2009-03710) and the University of Alicante (Project GRE12-03).