Catalysts proline aryl sulfonamide

Aldol additions of acetone (1) as a nucleophile to ketones without a-acidic protons are feasible. The proline-catalyzed aldol reaction between acetone (1) and 1-aryl-2,2,2-trifluoroethanone (128) led to tertiary alcohol 129 in good yield but with low stereoselectivity [146]. A proline-derived sulfonamide 130 performs much better (Table 3.10, entry 2). Kokotos prepared a prolinamide-thiourea catalyst 131, which under optimum conditions can be used in 2 mol%, even at 0°C (entry 3) [ 147], With proline, the reaction was completed within hours, while more stereoselective catalysts 130 and 131 required 2 days. So far, these are the catalysts of choice for this tran ormation [146-148]. 

Other sulfur-proline derivatives have been prepared and screened as catalysts in the intramolecular aldol reaction. Remarkably, sulfonamide 83a (10 mol%. Fig. 4.9) was an efQcient catalyst for the aldol reaction between aryl methyl ketones... 

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