HIGHLY DIASTEREOSELECTIVE ACETAL CLEAVAGES USING NOVEL REAGENTS PREPARED FROM ORGANOALUMINUM AND PENTAFLUOROPHENOL

被引:56
作者
ISHIHARA, K [1 ]
HANAKI, N [1 ]
YAMAMOTO, H [1 ]
机构
[1] NAGOYA UNIV,SCH ENGN,CHIKUSA KU,NAGOYA 46401,JAPAN
关键词
D O I
10.1021/ja00076a030
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Chiral acetals derived from aldehydes and (-)-(2R,4R)-2,4-pentanediol are cleaved selectively by organoaluminum reagents. The reaction proceeds via the retentive-alkylation process with >95% selectivities in most cases. Trialkylaluminum reagent is utilized for higher alkyl transfers, but for smaller alkyl transfers, a new reagent system, combining trialkylaluminum and the halophenols such as pentafluorophenol and 2,4,6-trichlorophenol, is employed. Chiral acetals derived from aldehydes and 1,3-butanediol are cleaved selectively by trialkylaluminum, even for smaller alkyl transfers. Oxetane is also exposed to these aluminum reagents, and the retentive-alkylation products are obtained stereoselectively. The reaction of acetals derived from (-)-(2R,4R)-2,4-pentanediol and ketones in the presence of a catalytic amount of aluminum pentafluorophenoxide produces reductively cleaved products with high diastereoselectivity. The reaction is a new means of diastereoselective cleavage of acetals: an intramolecular Meerwein-Ponndorf-Verley reductive and Oppenauer oxidative reaction on an acetal template.
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页码:10695 / 10704
页数:10
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