SYNTHESIS OF PENTASUBSTITUTED PYRIDINES - CYCLOADDITIONS OF N-VINYLICHETEROCUMULENES WITH 1-(N,N-DIETHYLAMINE)PROP-1-YNE

The reactions of N-vinyl carbodiimides 4 and 5, and N-vinyl ketenimine 6 with ynamine 7 in THF, chloroform, toluene, and xylenes at, respect ively, 0 degrees C, 25 degrees C, 100 degrees C, and 140 degrees C is shown. Pentasubstituted pyridines 8, 9, 11, and 12 an:obtained in very high yields through thermally controlled [2+2] or [4+2] competitive p rocesses. Additionally, when the temperature is raised, the N-vinyl he terocumulenes 5 and 6 undergo an electrocyclic ring closure of six ele ctrons driving to isoquinolines 10 and 13, respectively. (C) 1997 Else vier Science Ltd.