Yamamoto vinylogous aldol reaction

The Yamamoto vinylogous aldol reaction, in which bulky aluminium-based Lewis acids activate the aldehyde and also become part of the enolate, is stereodirected by 2,3-syn and 2,3-anti disubstitution of the aldehydes bulky -substituents favour 1,3-syn diol formation, whereas alkynyl groups lead to 1,3-anti products. The reaction of (g) a-branched enals with isatins may switch from vinylogous aldolization to a pericyclic pathway depending on the nature of the a-branch. °... 

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