J. C. Bardhan

Bio: J. C. Bardhan is an academic researcher. The author has contributed to research in topics: Sterol. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

The Dieckmann Condensation (Including the Thorpe‐Ziegler Condensation)

Abstract: The Dieckman condensation is an acetoacetic ester condensation in which a dicarboxylic ester is cyclized to a beta-ketonic ester through the action of a base. The dicarboxylic ester must have at least one alpha-hydrogen atom and the carbalkoxy groups must be situated that cyclization will result in a 4-membered ring or larger ring. Discovery and development of the reaction are generally credited to Dieckmann, who found that heating an adipic or a pimelic ester with sodium and a trace alcohol led to cyclization with formation of a cyclopentanone or a cyclohexanone. The Dieckmann condensation has proved useful for the preparation of a variety of carbocyclic and heterocyclic ketones and has been extended to the synthesis of 7 and 8-membered rings. Keywords: Dieckman condensation; cyclizations; Michael condensation; intermolecular ester; alkylation; acyloin condensation; failures

Selectivity of the generation of 3- and 4-carboxyalkyl radicals from substituted glutaric and adipic acids and their oxidative lactonization

Abstract: 1. The oxidative decarboxylation of acids with carboxyl groups at secondary and tertiary C atoms under the action of the S2O82−- Ag+ and S2O82−-Ag+- Cu2+ systems is at least an order of magnitude faster than that of acids with COOH groups at a primary C atom, as a result of which 3- and 4-carboxyalkyl radicals with the general formula R'RĊ(CH2)nCOOH (R is alkyl or phenyl, R′ is H or alkyl, n=2 or 3) are generated with > 90% selectivity from 2-substituted glutaric and adipic acids. 2. The 3- and 4-carboxyalkyl radicals are completely or partially converted under their generation conditions into lactones. The selectivity of the oxidative lactonization increases from 0.30 to 0.97 along the series of radicals C2H5ĊH(CH2)3COOH, C2H5ĊH(CH2)2COOH, ĊH2(CH2)3COOH, ĊH2(CH2)2COOH, (CH3)2Ċ(CH2)2-COOH, and C2H5ĊH(CH2)2COOH in the case of the S2O82−-Ag+ system and from 0.72 to 1 along this series in the case of the S2O82−- Ag+- Cu2+ system.