Synthesis of γ-Acetoxy β-Keto Esters Through Regioselective Hydration of γ-Acetoxy-α,β-alkynoates
摘要:
The At(I)-catalyzed regioselective hydration of gamma-acetoxy-alpha,beta-acetylinic ester by the assistance of a neighboring carbonyl group has beets developed. Varieties of simple primary, secondary, and tertiary gamma-acetoxy-alpha,beta-acetylinic esters, even those bearing sensitive functional group in the remote reaction sites, are selectively hydrated to the corresponding beta-keto esters. The reaction' tolerates a wide variety of other carboxylates, such as benzoates, propionates, acrylates, and pivalates, including chiral carboxylates with retention of the configuration. The broad substrate scope, including the derivatization of complex natural products and neutral and open air conditions, makes this atom economical approach very practical. O-18 labeling experiments disclose that the oxygen transposition occurs from the carboxylate group to the triple bond, not from water.
Highly Enantioselective Catalytic Alkyl Propiolate Addition to Aliphatic Aldehydes
作者:Mark Turlington、Albert M. DeBerardinis、Lin Pu
DOI:10.1021/ol900667g
日期:2009.6.4
A novel H8BINOL-based chiral ligand (S)-3 is found to catalyze the alkyl propiolate addition to aliphatic aldehydes in the presence of ZnEt2 and Ti(OiPr)4 at room temperature with excellent enantioselectivity (89−97% ee).
发现一种新型的基于H 8 BINOL的手性配体(S)-3在室温下在ZnEt 2和Ti(O i Pr)4的存在下以优异的对映选择性(89-97%)催化丙酸烷基酯加成到脂肪族醛中ee)。
Synthesis of New γ-Lactams with gem-Difluorinated Side Chains
A short and efficient approach has been designed for the synthesis of new γ-lactams that feature gem-difluorinated side-chains in position 4. The key steps involve 1,4-addition of nitroalkane anions on electrophilic gem-difluoroalkenes, followed by a cascade nitro reduction–heterocyclization. This flexible strategy also allows easy introduction of substituents in positions 3 or 5.