Abstract

CONVERSION OF CARBONYL FUNCTIONAL GROUP INTO METHYLENE GROUP BY TWO CHEMICAL STALWARTS: CLEMMENSEN REDUCTION & WOLFF– KISHNER REDUCTION

*Arpita Biswas, Anneswa Ghosh, Aparajita Paul, Uday Mandal, Kushal Nandi, Dr. Dhrubo Jyoti Sen and Dr. Dhananjoy Saha.

Abstract

Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zinc amalgam and concentrated hydrochloric acid. This reaction is named after Erik Christian Clemmensen, a Danish chemist. The original Clemmensen reduction conditions are particularly effective at reducing aryl–alkyl ketones, such as those formed in a Friedel–Crafts acylation. The two–step sequence of Friedel–Crafts acylation followed by Clemmensen reduction constitutes a classical strategy for the primary alkylation of arenes. With aliphatic or cyclic ketones, modified Clemmensen conditions using activated zinc dust in an anhydrous solution of hydrogen chloride in diethyl ether or acetic anhydride is much more effective. The Wolff–Kishner reduction is a reaction used in organic chemistry to convert carbonyl functionalities into methylene groups. In the context of complex molecule synthesis, it is most frequently employed to remove a carbonyl group after it has served its synthetic purpose of activating an intermediate in a preceding step. As such, there is no obvious retron for this reaction. Originally reported by Nikolai Kischner in 1911 and Ludwig Wolff in 1912, it has been applied to the total synthesis of scopadulcic acid B, aspidospermidine and dysidiolide. The Wolff-Kishner reduction reaction usually proceeds under strongly basic conditions in the presence of a large amount of heat. This reaction is known to require a polar protic solvent. On the other hand, the Clemmensen reduction reaction is known to be performed under highly acidic conditions.

Keywords: Clemmensen reduction is a chemical reaction described as a reduction of ketones (or aldehydes) to alkanes using zinc amalgam and concentrated hydrochloric acid. This reaction is named after Erik Christian Clemmensen, a Danish chemist. The original Clemmen