BASE-INDUCED CYCLOADDITION OF TOSYLMETHYL OR (TERT-BUTOXYCARBONYL)METHYL ISOCYANIDE TO 1,4-DISUBSTITUTED 2,3-DINITRO-1,3-BUTADIENES - ACCESS TO 2,3-DISUBSTITUTED 4-ETHYNYLPYRROLES

The reactions of 1,4-disubstituted 23-dinitro-1,3-butadienes 1a-g in T HF with isocyanides XCH(2)NC (TosMIC, X = tosyl; TBICA, X = COOBu(t)) and DBU furnish good to moderate yields of 2,3-disubstituted 4- ethyny lpyrroles 5a-g or 6a-g. In the reaction of Ig with TosMIC and DBU the nitrovinyl pyrrole 7g and the 3,3'-dipyrrole 4g are also isolated as b y-products. A mechanism involving sequential base-induced addition, el imination and cyclization steps is advanced to account for the formati on of the isolated products.