Mgh. Vicente et al., SYNTHESIS AND CYCLOADDITION REACTIONS OF PYRROLE-FUSED 3-SULFOLENES -A NEW VERSATILE ROUTE TO TETRABENZOPORPHYRINS, Tetrahedron letters, 38(20), 1997, pp. 3639-3642
Pyrrole-fused 3-sulfolenes 2a,b were prepared from the corresponding a
lpha,beta-unsaturated sulfone 1. These pyrroles undergo thermal extrus
ion of sulfur dioxide to produce highly reactive o-quinodimethanes whi
ch can be trapped in Diels-Alder reactions. The resulting pyrroles are
important starting reagents in porphyrin synthesis. (C) 1997 Elsevier
Science Ltd.