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

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 aldehydes4b) 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)