Experimental and theoretical studies of (4 + 1) annulations between α‐oxoketenes and stable phosphorous, nitrogen, or sulfur ylides
Résumé
α‐Oxoketenes generated in situ by a microwave‐assisted Wolff rearrangement at 170°C were found to react with stabilized sulfur ylides in (4 + 1) annulation processes to afford functionalized 3‐hydroxyfurans. Theoretical mechanistic investigations revealed that the reaction proceeds in two steps via a short‐lived betaine intermediate, a general feature of the reactions of α‐oxoketenes with stable phosphorous, nitrogen, and sulfur ylides.