Preparation of spirobenzoisothiazole-isoxazole dioxides from difithiated C(alpha),O-oximes and methyl 2-(aminosulfonyl)benzoate

摘要

Several dilithiated C(alpha),O-oximes were prepared in excess lithium diisopropylamide-tetramethylethylenediamine (LDA/TMEDA) and condensed with methyl 2-(aminosulfonyl)benzoate followed by acid cyclization of intermediates to spiro(benzoisothiazole-isoxazole) dioxides, a new spiro and fused-ring system. Distortionless enhancement by polarization transfer (DEPT) and liquid chromatography mass spectrometry (LCMS) for all products, as well as X-ray single crystal analysis on a representative product, were especially relevant for structure confirmation in this synthesis.