Preparation of Cyclic .ALPHA.-Hydroxy Ketones from .DELTA.- and .EPSILON.-Keto Acids Induced by the Generation of a Novel Acyl Anion Equivalent from the Carboxyl Group.
An improved method for the transformation of keto acids into cyclic α-hydroxy ketones, induced by the electrochemical generation of a novel acyl anion equivalent from the carboxy group, has been developed. Both five- and six-membered rings were constructed by constant-current electrolysis of δ- and ε-keto acids in the presence of Bu3P using an undivided cell equipped with a graphite anode and a Pt cathode. Attempts to prepare four- and seven-membered ring carbocycles were unsuccessful. The electrochemical reaction was found to be highly stereoselective when cyclization took place onto cyclopentanone and substituted cyclohexanone rings. Stereochemical aspects of the formation of bicyclic products, especially those having a bicyclo[4.3.0]skeleton, are discussed.
Generation of acyl anion equivalents by in situ cathodic reduction of acyl tributylphosphonium ions anodically generated from tributylphosphine and carboxylic acids: preparation of α-hydroxy cycloalkanones from keto acids
The preparation of α-hydroxy cycloalkanones from keto acids was effectively achieved by constant current electrolysis in the presence of Bu3P in an undivided cell under an N2 atmosphere, where the α-oxy ylides generated by the in situ cathodic reduction of acyl tributylphosphonium ions, formed anodically from tributylphosphine and carboxylic acids, seems to function as a novel acyl anion equivalent.
Studies toward the syntheses of functionally substituted .gamma.-butyrolactones and spiro-.gamma.-butyrolactones and their reaction with strong acids: a novel route to .alpha.-pyrones
作者:A. K. Mandal、D. G. Jawalkar
DOI:10.1021/jo00271a023
日期:1989.5
Treibs; Muehlstaedt, Chemische Berichte, 1954, vol. 87, p. 407,410