NEW DIELS-ALDER REACTIONS OF 3-VINYLINDOLES WITH AN ARYNE - SELECTIVEACCESS TO FUNCTIONALIZED [A]ANELLATED CARBAZOLES

New results for the reactions of donor- and acceptor-substituted 3-vin ylindoles with aryne and structurally related 3,4-pyridyne are describ ed. Aryne reacts in Diels-Alder reactions as a dienophile to give rise to a variety of [a]anellated carbazoles in a one-step procedure, Addi tionally, aryne is involved in an ene or conjugate addition reaction w ith the initially formed [4 + 2]cycloadduct. Reaction of methyl (E)-3- (N-methylindol-3-yl)propenoate 6 in the presence of air gives besides the expected Diels-Alder product a new benzoxepino [b]indole derivativ e 14, The Diels-Alder reactions of the 3-vinylindoles with in situ gen erated 3,4-pyridyne are difficult to control and no cycloadducts with the required purity could be isolated.