The reaction of 4-methoxyphenylisonitrile with phenylacetylene and AIBN produces a novel cyclopenta-fused quinoxaline through addition of 2-cyanoprop-2-yl radical to the alkyne; the resulting vinyl radical attacks isonitrile to afford an imidoyl radical, which gives rise to a tandem 5-exo, 6-endo cyclisation. The whole process entails a new example of a rare 4 + 1 radical annulation. The cyanopropyl radical can also attack isonitrile to yield small amounts of quinolines deriving from 4 + 2 and 3 + 2 annulation between the resulting imidoyl radicals and phenylacetylene. The oxidation step leading to the final aromatic products involves the starting isonitrile, which is converted to an a-unsubstituted imidoyl radical and affords 2-unsubstituted quinolines. This behaviour was also found in cyclisations of biphenyl-2-ylisonitrile under various radical conditions. Finally, the title reaction gives small amounts of an alpha,beta-unsaturated nitrile, which can arise from a spirocyclohexadienyl radical through fragmentation and subsequent beta-scission of the resulting iminyl. This could be the first, direct evidence of the intermediacy of iminyl radicals in the rearrangements of the spirocyclohexadienyls obtained by 3 + 2 annulation between imidoyl radicals and alkynes.

Radical Annulations and Cyclisations with Isonitriles: the Fate of the Intermediate Imidoyl and Cyclohexandienyl Radicals / D., Nanni; P., Pareschi; Rizzoli, Corrado; Sgarabotto, Paolo; A., Tundo. - In: TETRAHEDRON. - ISSN 0040-4020. - 51:(1995), pp. 9045-9062. [10.1016/0040-4020(95)00348-C]

Radical Annulations and Cyclisations with Isonitriles: the Fate of the Intermediate Imidoyl and Cyclohexandienyl Radicals

RIZZOLI, Corrado;SGARABOTTO, Paolo;
1995-01-01

Abstract

The reaction of 4-methoxyphenylisonitrile with phenylacetylene and AIBN produces a novel cyclopenta-fused quinoxaline through addition of 2-cyanoprop-2-yl radical to the alkyne; the resulting vinyl radical attacks isonitrile to afford an imidoyl radical, which gives rise to a tandem 5-exo, 6-endo cyclisation. The whole process entails a new example of a rare 4 + 1 radical annulation. The cyanopropyl radical can also attack isonitrile to yield small amounts of quinolines deriving from 4 + 2 and 3 + 2 annulation between the resulting imidoyl radicals and phenylacetylene. The oxidation step leading to the final aromatic products involves the starting isonitrile, which is converted to an a-unsubstituted imidoyl radical and affords 2-unsubstituted quinolines. This behaviour was also found in cyclisations of biphenyl-2-ylisonitrile under various radical conditions. Finally, the title reaction gives small amounts of an alpha,beta-unsaturated nitrile, which can arise from a spirocyclohexadienyl radical through fragmentation and subsequent beta-scission of the resulting iminyl. This could be the first, direct evidence of the intermediacy of iminyl radicals in the rearrangements of the spirocyclohexadienyls obtained by 3 + 2 annulation between imidoyl radicals and alkynes.
1995
Radical Annulations and Cyclisations with Isonitriles: the Fate of the Intermediate Imidoyl and Cyclohexandienyl Radicals / D., Nanni; P., Pareschi; Rizzoli, Corrado; Sgarabotto, Paolo; A., Tundo. - In: TETRAHEDRON. - ISSN 0040-4020. - 51:(1995), pp. 9045-9062. [10.1016/0040-4020(95)00348-C]
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2313744
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 113
  • ???jsp.display-item.citation.isi??? 110
social impact