Domino Michael-aldol reactions chromene synthesis

The reaction of salicylaldehydes with a,P-unsaturated compounds which can lead to chromenes, chromans and other heterocycles has been reviewed <07OBC1499> and details of their reaction with allenic esters and ketones have been published <07CEJ3701>. A proline-catalysed benzoic acid-promoted asymmetric synthesis of chromene-3-carbaldehydes involves a domino oxa-Michael - aldol reaction with a,P-unsaturated aldehydes the ee range is 83-98% (Scheme 11) <07CEJ574>. 

P. Kotame, B.-C. Hong, J.-H. Liao, Tetrahedron Lett. 2009, 50, 704—707. Enantioselective synthesis of the tetrahydro-6//-benzo[c]chromenes via domino Michael-aldol condensation control of five stereocenters in a quadruple-cascade organocatalytic multi-component reaction. 

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