Acyl halide-aldehyde cyclocondensation reactions

Nelson SG, Spencer KL (2000) Enantioselective (3-amino acid synthesis based on catalyzed asymmetric acyl halide-aldehyde cyclocondensation reactions. Angew Chem Int Ed 39 1323-1325... 

Nelson SG, Zhu C, Shen X (2004) Catalytic asymmetric acyl halide — aldehyde cyclocondensation reactions of substituted ketenes. J Am Chem Soc 126 14-15... 

The use of Al(III) complexes as catalysts in Lewis acid mediated reactions has been known for years. However, recent years have witnessed interesting developments in this area with the use of ingeiuously designed neutral tri-coordinate Al(lll) chelates. Representative examples involving such chelates as catalysts include (1) asymmetric acyl halide-aldehyde cyclocondensations, " (2) asymmetric Meerwein-Schmidt-Ponndorf-Verley reduction of prochiral ketones, (3) aldol transfer reactions and (4) asymmetric rearrangement of a-amino aldehydes to access optically active a-hydroxy ketones. It is important to point out that, in most cases, the use of a chelating ligand appears critical for effective catalytic activity and enantioselectivity. 

Acyl Halide-Aldehyde Cyclocondensation (AAC) Reactions. Treatment of ( -symmetric ligand bis(sulfonamide) A with 1 equiv of trimethylaluminum generated the triamine-Al complex (C), which catalyzed the aldehyde ketene [2 + 2] cyclad-dition. 

Nelson SG, Peelen TJ, Wan Z (1999) Catalytic asymmetric acyl halide - aldehyde cyclocondensations. A strategy for enantioselective catalyzed cross Aldol reactions. J Am Chem Soc... 

Nelson SG, Wan Z (2000) Catalytic asymmetric propionate Aldol reactions via acyl halide — aldehyde cyclocondensations. Org Lett 2 1883-1886... 

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