Aza-Wittig Reaction of <i>N</i>-Vinylic Phosphazenes with Carbonyl Compounds. Azadiene-Mediated Synthesis of Isoquinolines and 5,6-Dihydro-2<i>H</i>-1,3-oxazines

Abstract

N -Vinylic phosphazenes 4 are obtained by reaction of phosphorus ylide 5 and nitriles 6 . Aza-Wittig reaction of phosphazenes 4 with aldehydes leads to the formation of 2-azadienes 1, which are easily converted into isoquinolines 2 . Reaction of conjugated phosphazenes 4 with ethyl glyoxalate affords 5,6-dihydro-2 H -1,3-oxazines 9 in a regio- and stereoselective fashion, while heterodienes 1 react with ethyl glyoxalate and diethyl ketomalonate giving 1,3-oxazines 11 and 12 .