Substitution reactions of nitrothiophens with the 2-Nitropropan-2-ide ion

Abstract

The reactions of the lithium and tetraalkylammonium salts of 2- nitropropane with 2-nitrothiophen (3), 2,5-dinitrothiophen (8), 2-iodo-5-nitrothiophen (7), 2,4-dinitrothiophen (16) and 2-(1-methyl-1-nitroethyl)-5-nitrothiophen (2) have been studied. The compounds (3) and (16) give observable Meisenheimer adducts (11) and (17) respectively whose N.M.R. data are discussed. Decomposition of adduct (11) gives, depending on reaction conditions, 2-isopropyl-5- nitrothiophen (5), 2,2-bis(5-nitro-2-thienyl)propane (6) and 2-(5- nitro-2-thienyl)propan-2-ol (4). Possible mechanisms for these trans- formations are proposed. Reaction of the nitro compounds (7) and (8) gives initially the compound (2) by an S_NAr process. The S_RN1 reactions of (2) with the above salts of 2-nitropropane, the sodium salt of diethyl 2-methylmalonate, and sodium benzenethiolate are presented. The last-named reaction in the presence of benzenethiol proceeds anomalously to give the reduced product (5) as well as the normal S_RN1 product 1-methyl-1-(5-nitro-2-thienyl)ethyl phenyl sulfide (21).