Reaction with aldimines

The lithium enolates of thioesters are also amenable to this transformation, involving transmetalation, to Et2AlCl, producing the corresponding aluminum enolates which undergo Mannich-type reaction with aldimine 48 subsequent intramolecular cyclization gave /i-lactams in fairly good yields (Scheme 6.28) [49]. 

This protocol could be directly applied in the addition of 2 silyloxy furans to keti mines and the generation of a quaternary chiral center. Using electronically highly activated a ketoimine esters 24 as substrates, the same chiral silver phosphine catalyst (10mol%) as previously used in reactions with aldimines delivered the desired Mannich products in good yields, good diastereoselectivity, and up to 94% ee (Table 5.3) [9]. 

Chiral phosphoric add is also effective for aza-Diels-Alder reactions. Danishefsky s diene underwent aza-Diels-Alder reaction with aldimines by means of 21e in the presence of acetic add to give the cycloadduds with high enantios-eledivities (Equation 10.43) [89]. Brassard s diene also partidpated in the aza-Diels-Alder readion under the influence of 21j to give 5-ladams with excellent enantioselectivities [90]. 

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