Nitrobutadienes from β-nitrothiophenes:: valuable building-blocks in the overall ring-opening/ring-closure protocol to homo- or hetero-cycles

beta-Nitrothiophenes undergo a facile ring-opening process when treated with secondary amines in ethanol ( in the presence of AgNO3, but for 3,4-dinitrothiophene), providing interesting polyfunctionalized linear nitro- or dinitro-butadienic building-blocks, which can be further manipulated and eventually exploited for the preparation of targets of various nature. In particular, a great variety of homo- and hetero-cyclic compounds may be obtained and some representative results in this field, relevant to synthetic, mechanistic and stereochemical aspects, are reported herein.