- Stereoselective functionalisation of SuperQuat enamides: asymmetric synthesis of homochiral 1,2-diols and α-benzyloxy carbonyl compounds
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Homochiral (E)- and (Z)-enamides derived from SuperQuat (S)-4-phenyl-5,5-dimethyl-oxazolidin-2-one undergo highly diastereoselective epoxidation upon treatment with dimethyldioxirane. Subsequent epoxide opening with meta-chlorobenzoic acid proceeds via a stereoselective SN1-type process, with retention of configuration, to give the corresponding 1′-m-chlorobenzoyl-2′-hydroxy derivatives. Treatment of the SuperQuat enamides with mCPBA effects this two-step transformation in one pot. Reductive cleavage of the isolated 1′-m-chlorobenzoyl-2′-hydroxy derivatives (≥96% de) generates homochiral 1,2-diols in ≥96% ee. Alternatively, regioselective lithiation of the enamide at C(1′) with tBuLi followed by reaction with an aromatic aldehyde and in situ O-benzylation generates a 1′-(benzyloxy-aryl-methyl) substituted enamide with high diastereoselectivity. Subsequent oxidative cleavage of the enamide C{double bond, long}C bond with NaIO4/RuCl3 followed by methanolysis of the resultant N-acyl fragment furnishes an O-benzyl protected α-hydroxy methyl ester in high ee.
- Aciro, Caroline,Davies, Stephen G.,Garner, A. Christopher,Ishii, Yutaka,Key, Min-Suk,Ling, Kenneth B.,Prasad, R. Shyam,Roberts, Paul M.,Rodriguez-Solla, Humberto,O'Leary-Steele, Catherine,Russell, Angela J.,Sanganee, Hitesh J.,Savory, Edward D.,Smith, Andrew D.,Thomson, James E.
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p. 9320 - 9344
(2008/12/22)
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- Convenient syntheses of 2-alkyl(Aryl)-4,5-diphenyloxazoles and 2-alkyl(Aryl)-4-phepyloxazoles
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The synthetic methods to prepare 2-alkyl(aryl)-4,5-diphenyloxazoles and 2-alkyl(aryl)-4-phenyloxazoles were improved on the basis of a mechanistic study of oxazole formation from α-hydroxy ketones (carboxylic esters of benzoin and phenacyl alcohols). By these methods, seven trisubstituted oxazoles and twelve disubstituted oxazoles of the title compounds were prepared.
- Pei, Weiwei,Li, Shaohui,Nie, Xiaoping,Li, Yiwei,Pei, Jian,Chen, Bingzi,Wu, Jie,Ye, Xiulin
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p. 1298 - 1304
(2007/10/03)
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