An Efficient Method for the Selective Reduction of 2-Aryl-1-Nitroalkenes to 2-Aryl-1-Nitroalkanes by 2-Phenylbenzimidazoline

Abstract

Nitroalkanes have recently been demonstrated to be useful synthetic intermediates for a variety of trans- formations. They have, for example, been converted to carbonyl, la) nitrile oxide,^lb) and amino compounds.^1c) Especially, 2-aryl-1-nitroalkanes are important in connection with the synthesis of biochemically and pharmacologically interesting compounds. ²⁾ They have also been used as synthetically equivalent to enamines and enolates.³⁾ A widely employed method⁴⁾ for the synthesis of nitroalkanes involves NaBH₄ reduction of conjugated nitroalkenes. The NaBH₄ reduction of nitro- alkenes derived from aliphatic aldehydes^4b) or ketones⁵⁾ usually proceeds smoothly in good yields. However, the reduction of 2-aryl-1-nitroalkenes with NaBH₄ produces low yields of products due to undesired side reactions such as dimerization.⁴⁾