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 synthesis of 2-alkyl-substituted 2-hydroxyglutaric acid γ-lactones
3-Alkyl-1,2-cyclopentanediones 1 are transformed into 2-alkyl-2-hydroxyglutaric acid gamma-lactones 3 in up to 83% isolated yields and up to 96% ee, affording a simple access to many bioactive compounds, including diacylglycerol lactones (DAG-lactones). (c) 2006 Elsevier Ltd. All rights reserved.
Carboxyl Group-Directed Iridium-Catalyzed Enantioselective Hydrogenation of Aliphatic γ-Ketoacids
occurrence of chiral induction involving a hydrogen–hydrogen interaction between a hydride on the iridium atom and the substituent on the oxazoline ring of the ligand, and on the basis of the calculations, we proposed a catalytic cycle involving only Ir(III), which differs from the Ir(III)/Ir(V) catalytic cycle that operates in the hydrogenation of α,β-unsaturated carboxylic acids.
A method for the aerobic cascade oxidation of cyclopentane-1,2-diones using metal porphyrins as catalysts, yielding hydroxydiacids 2, ketoacid 3 and diketoacids 4 which are the intermediates of important biologically active compounds is reported. This method is operationally simple and can be employed under ambient conditions.