Methyleneketenes and methylenecarbenes. II. A new phenolic ring synthesis: 2-Naphthol from o-tolualdehyde

Abstract

Flash vacuum pyrolysis of 2,2-dimethyl-5-(2?-methylbenzylidene)-1,3- dioxan-4,6-dione (1) at 420-620? gives 2-naphthol in 95-100% yield. The reaction probably involves an intermediate 2- methylbenzylideneketene, which undergoes consecutive [1,5] hydrogen migration and cyclization reactions. Substituted 2-naphthols and a phenol (biphenyl-3-ol) have been synthesized in a similar way.