Cupration of Organomercurials: A Mild Method for the Intramolecular Addition of Organometallics to Ester Groups

摘要

Addition of Grignard and alkyllithium reagents to carbonyl groups is one of the most widely used applications of organometallics in organic synthesis. However, its intramolecular version has never been fully developed, owing to the high reactivity ofthe reagents required to generate the CMgX or CLi group in the molecule already containing an unprotected carbonyl function. Alternatives involving less reactive organometallic species (B, Si, Sn, Zn, Cr, and Ni) are confined to allylic, benzylic, or vinylic halides and enol triflates as precursors. Much more successful is the Sm(II)- and Yb(II)-mediated cy-clization of halo ketones and halo esters. We have recently shown that the intramolecular addition to an aldehyde group in 1 and 2 can be accomplished via activating the neighboring CHgX moiety by organo-cuprates (Scheme 1). Similarly, intramolecular addition across an activated double bond (1,4-addition) has also been observed. Herein, we describe related intramolecular additions to ester groups.