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Within an overall ring-opening/ring-forming protocol, the (E,E)-4-methylthio-2-nitro-3-phenylsulfonyl-1-pyrrolidino-1,3-butadiene (7) [derived from the initial opening of 3-nitro-4-(phenylsulfonyl)thiophene (6) with pyrrolidine and silver nitrate in EtOH] is revealed to be an excellent precursor of nitro(phenylsulfonyl) derivatives of ring-fused aromatic (naphthalene, phenanthrene) or heteroaromatic (benzothiophene) compounds whose substitution pattern cannot be easily achieved by conventional methods. The key step is represented by a thermal electrocyclic rearrangement of (E,E)-1-aryl-4-methylsulfonyl-2-nitro-3-phenylsulfonyl-1,3-butadienes (9), which, thanks to proper geometric and electronic factors, occurs in unprecedentedly mild conditions and is followed by an irreversible, concerted syn beta-elimination of methanesulfinic acid to aromatize the newly formed cyclohexadienic ring.

β-Nitrothiophenes undergo a facile ring-opening process when treated with secondary amines in ethanol (in the presence of AgNO 3 , 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.

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