An aza-Wittig/pi-furan cyclization approach toward the homoerythrina alkaloid (+/-)-selaginoidine

reaction: see text] A one-pot procedure was developed to efficiently prepare hexahydroindolinones containing a tethered furan ring. Reaction of a furanyl azide with Bu3P delivered the iminophosphorane, which was allowed to react with 1-methyl-(2-oxocyclohexyl)acetic acid to give the desired hexahydroindolinone ring system. Further treatment with trifluoroacetic acid afforded the tetracyclic lactam skeleton found in the alkaloid (+/-)-selaginoidine.