Tandem thio-Michael-aldol reaction

Wang and coworkers found that the quinine-derived thiourea catalyst 81b (1 mol%) was also highly reactive and enantioselective for the tandem thio-Michael-aldol reaction of various 2-mercaptobenzaldehydes (103) with a,P-unsaturated oxazolidi-nones (104), furnishing benzothiopyranes (105) with three stereogenic centers in... 

Scheme 6.130 Proposed mechanism of the 121-catalyzed enantioselective thio-Michael-aldol tandem reaction of 2-mercaptobenzaldehydes with a,P-unsaturated oxazolidinones bifunctional activation through thiourea 121.

Scheme 6.131 Typical thiochromanes obtained from the 121-catalyzed asymmetric thio-Michael-aldol tandem reaction between various 2-mercaptobenzaldehydes and a, 3-unsaturated oxazolidinones.

Stereoselective thio-Michael-aldol tandem reaction has been reported, using a mixture of PhSLi, O -unsaturated ester (148), and aldehyde (149) in CH2CI2 (Scheme 21). The adducts, j0-hydroxy-a-(l-phenylthioalkyl) esters (150), were obtained in moderate... 

Lewis acid-catalyzed tandem Michael imino-aldol reactions enable the one-pot synthesis of 7-acyl-(5-lactams from a, j6-unsaturated thio-esters, silyl enolates and imines [15]. For the initial Michael addition, the combination of SbClj with Sn(OTf>3 (5 mol %) proved to be efficient. However, after the addition of the imino compound the iminoaldol product was isolated in moderate yield. For the enhancement of turnover and yield, Sc(OTf)3, once again proved to be the Lewis acid of choice (Scheme 4, 15 16 = 81 19, 94%). 

---