O. Chavignon et al., REACTIONS OF (VINYLIMINO)PHOSPHORANES AND RELATED-COMPOUNDS - ACCESS TO THE AZACARBOLINES AND APLYSINOPSINES, Journal of organic chemistry, 59(21), 1994, pp. 6413-6418
Aza-Wittig-type reactions of iminophosphoranes 3a, 14a,b and 19, deriv
ed from azidovinyl (or -phenyl) derivatives and triphenylphosphine, wi
th methyl or phenyl isocyanates were used to construct the framework o
f the azacarboline structures 7a,b-10, 20, 21a-d and aplysinopsine-typ
e alkaloids 17a-d by electrocyclic ring closure or heterocumulene-medi
ated annelation.