Oxazinanones as chiral auxiliaries: synthesis and evaluation in enolate alkylations and aldol reactions
作者:Stephen G. Davies、A. Christopher Garner、Paul M. Roberts、Andrew D. Smith、Miles J. Sweet、James E. Thomson
DOI:10.1039/b604073j
日期:——
Homochiral beta-amino esters (prepared on multigram scale by lithium amide conjugate addition) are readily transformed into oxazinanones. N-acyl derivatives of oxazinanones undergo stereoselective enolate alkylation reactions, with higher stereoselectivities observed for the enolate alkylation of (R)-N-propanoyl-4-iso-propyl-6,6-dimethyl-oxazinan-2-one than the corresponding Evans oxazolidin-2-one
高手性β-氨基酯(通过酰胺锂共轭物的加成以克数制)很容易转化为恶二酮。恶唑烷酮的N-酰基衍生物经历立体选择性烯酸酯烷基化反应,与相应的Evans相比,(R)-N-丙酰基-4-异丙基-6,6-二甲基-恶嗪烷-2-酮的烯酸酯烷基化观察到更高的立体选择性。恶唑烷-2-酮。恶唑烷酮内的AC(4)-异丙基立体定向基团比类似的C(4)-苯基取代基具有更高的立体选择性。恶唑烷酮骨架内的C(6)处的宝石二甲基取代促进水解时的排他性外环裂解,从而以高收率提供α-取代的羧酸衍生物和母体恶嗪酮。一系列芳香族和脂肪族醛与(R)-N-丙酰基-4-异丙基-6,6-二甲基-恶二嗪-2-酮的氯钛烯酸酯的不对称醛醇缩合反应具有出色的非对映选择性。醛醇缩合产物的水解得到同手性的α-甲基-β-羟基-羧酸。