New carbanionic access to 3-vinylindoles and 3-vinylbenzofurans.
[reaction: see text] A simple route to 3-vinylbenzofurans, 3-vinylfuropyridines, and 3-vinylindoles from readily accessible acetylenic precursors is described. A standard halogen-lithium exchange triggers an irreversible addition on the triple bond, according to a 5-exo-dig heterocyclization process, followed by a lithium ethoxide elimination. A final isomerization of the exocyclic allene provides a 1,3-dienic system that can react with acrylates, in thermal or hyperbaric conditions, to provide the expected [4+2] cycloadducts.
Le Strat
Frédéric
F
Laboratoire des Fonctions Azotées & Oxygénées Complexes de l'IRCOF, UMR 6014 CNRS, Université de Rouen, 76821 Mont St. Aignan, France.
Maddaluno
Jacques
J