Enzyme Promiscuity as a Remedy for the Common Problems with Knoevenagel Condensation
作者:Dominik Koszelewski、Ryszard Ostaszewski
DOI:10.1002/chem.201901491
日期:2019.8
lipase‐catalyzed tandemreaction toward α,β‐enones/enoesters is presented. For the synthesis of the desired products the tandem process based on enzyme‐catalyzed hydrolysis and Knoevenagel reaction starting from enol acetates and aldehyde is developed. The relevant impact of the reaction conditions including organic solvent, enzyme type, and temperature on the course of the reaction was revealed. It
annulation of 2-iodo enol esters leading to 4- and 3,4-substituted isocoumarins was accomplished selectively at room temperature. Coupling of 2-iodo benzoic acids with enolates that were produced in situ from the simple esters was also performed to produce isocoumarins under analogous reaction conditions. Owing to the mildness of the current protocol, 4-acyl 3-substitutedisocoumarins were efficiently produced
The formal insertion of dimethoxycarbene (1a) into the acidic
C–H bond of pentane-2,4-dione (9a), methyl acetoacetate (9b),
3-methylpentane-2,4-dione (9c) and 1,3-diphenylpropane-1,3-dione (9d) is
reported as well as the insertion of 3-benzoyloxazolidin-2-ylidene (1b)
into 9c. The β-dicarbonyl compounds 9 are known to be
equilibrated with their corresponding enols in benzene solution and the
insertions appear to proceed by proton abstraction from the enol
tautomers of 9 to generate enolate anions and either a dimethoxymethyl
cation (from 1a) or a 3-benzoyloxazolidin-2-ium cation (from 1b).
Collapse of these ion pairs at the carbon atom of the enolate yields the
major product. Formal insertion of 1a into the O–H bond of the
enol tautomer of anthrone (12) is also reported.
Highly Stereoselective Oxidative Esterification of Aldehydes with β-Dicarbonyl Compounds
作者:Woo-Jin Yoo、Chao-Jun Li
DOI:10.1021/jo0606103
日期:2006.8.1
Copper-catalyzed oxidative esterification of aldehydes with beta-dicarbonyl compounds was developed using tert-butyl hydroperoxide as an oxidant. In general, the enol esters were synthesized in good yields ( up to 87%) and high stereoselectivity under the optimized reaction conditions.