A new spiro annelation reaction in the isoxazole series: applications and limits

Abstract

The isoxazole-5-carboxylates (5) and (6) reacted with 1,3-diphenylguanidine and NaH to give, besides the corresponding amides (7) and (8), the 1 -oxa-2,6,8-triazaspiro[4.4] nonane derivatives (9) and (10), respectively; the latter compounds could also be obtained by partial conversion of (7) and (8) with a strong base. The limits of this spiro-cyclization reaction were shown through a detailed investigation of the behaviour of variously substituted isoxazoles towards the same reagents.