Substitution reactions of nitrothiophens. IV. Limitations in scope of the SN(AEAE) reaction in thienylalkyl derivatives

Abstract

The reactions of 5-nitro-3-thienylethyl chloride and acetate with lithium 2-nitropropan-2-ide (1)give excellent yields of the C-alkylate, 4-(1,2-dimethyl-2-nitropropyl)-2-nitrothophen, by the S_N(AEAE)mechanism. The cyano group is not a sufficiently activating substituent to support the S_N(AEAE)process and 4-cyano-2-thienyl-methyl and -ethyl chlorides with the salt (1) give O-alkylated products by an S_N2 mechanism. The occurrence of S_N (AEAE) reactions with other nucleophiles is difficult to prove but benzenethiolate and 4-nitro-2-thienylmethyl acetate do react by this mechanism to give a moderate yield of 4-nitro-2-thienylmethyl phenyl sulfide.