Cm. Camaggi et al., RADICAL ANNULATIONS WITH NITRILES - NOVEL CASCADE REACTIONS OF CYANO-SUBSTITUTED ALKYL AND SULFANYL RADICALS WITH ISONITRILES, Tetrahedron, 54(21), 1998, pp. 5587-5598
New radical annulation reactions are described involving addition of c
yano-substituted alkyl and sulfanyl radicals to aromatic isonitriles.
The tandem cyclisation of the resulting imidoyl radicals onto the cyan
o group affords cyclopenta- and thienoquinoxalines, respectively. The
intervention of the isonitriles in the aromatisation process of the cy
ctohexadienyl radicals is discussed as well as the regiochemistry of t
he cyclisation of the iminyl radicals obtained by addition of the imid
oyls to the nitrile moiety. The hypothesis of an exclusive 6-membered
ring closure onto the aromatic ring is also supported by the results o
f semiempirical AM1 calculations. (C) 1998 Elsevier Science Ltd. All r
ights reserved.