Synthesis of chiral hydroxylated cyclopentanones and cyclopentanes
摘要:
A method for the synthesis of enantiomeric 1,3-dihydroxy and 2,3-dihydroxy cyclopentanones, starting from a commercially available 3-methyl-cyclopentane-1,2-dione 1, is described. Dione 1 was subjected to asymmetric 3-hydroxylation to afford 3-methyl-3hydroxy-1,2-dione 2. The carbonyl groups in 2 were selectively differentiated by converting them either in dimethylacetal 5 or acetonide 6. Stereoselective reduction of those acetals by using NaBH4 afforded chiral methyl 1,2-dihydroxy cyclopentanone 9 and 1,3-dihydroxy cyclopentanone 10, respectively. The diols obtained were further converted to the corresponding diastereomeric triols 11-13 by hydride reduction. (c) 2006 Elsevier Ltd. All rights reserved.
Asymmetric oxidation of 3-alkyl-1,2-cyclopentanediones. Part 2: Oxidative ring cleavage of 3-alkyl-1,2-cyclopentanediones: synthesis of 2-alkyl-γ-lactone acids
Ti(OiPr)4/diethyl tartrate/tBuOOH system oxidizes 3-alkyl-1,2-cyclopentanediones resulting in hydroxylated ringcleavage products 2-alkyl-γ-lactone acids, in high enantioselectivity (∼95% ee) and satisfactory isolated yields (up to 55%).
Ti(O i Pr)4 /酒石酸二乙酯/ t BuOOH体系氧化3-烷基-1,2-环戊二酮,生成羟化的环裂解产物2-烷基-γ-内酯酸,对映体选择性高(〜95%ee),令人满意单产(最高55%)。
Asymmetric oxidation of 3-alkyl-1,2-cyclopentanediones. Part 1: 3-Hydroxylation of 3-alkyl-1,2-cyclopentanediones
3-Alkyl-1,2-cyclopentanediones undergo asymmetric 3-hydroxylation with the Sharpless Ti-complex resulting in enantiomeric 3-hydroxy carbonyl compounds with ee up to 95% in yields of 22-40%. (C) 2002 Elsevier Science Ltd. All rights reserved.
Synthesis of chiral hydroxylated cyclopentanones and cyclopentanes
A method for the synthesis of enantiomeric 1,3-dihydroxy and 2,3-dihydroxy cyclopentanones, starting from a commercially available 3-methyl-cyclopentane-1,2-dione 1, is described. Dione 1 was subjected to asymmetric 3-hydroxylation to afford 3-methyl-3hydroxy-1,2-dione 2. The carbonyl groups in 2 were selectively differentiated by converting them either in dimethylacetal 5 or acetonide 6. Stereoselective reduction of those acetals by using NaBH4 afforded chiral methyl 1,2-dihydroxy cyclopentanone 9 and 1,3-dihydroxy cyclopentanone 10, respectively. The diols obtained were further converted to the corresponding diastereomeric triols 11-13 by hydride reduction. (c) 2006 Elsevier Ltd. All rights reserved.