A Convenient Synthesis of 2H-1,4-Benzoxazines, 3H-Indol-3-ones, and 2,3-Dihydrobenzoxazoles

Abstract 3,5-Di-tert-butyl-1,2-benzoquinone 1-oxime (1b) reacted with ester ylides 2a,b to give the corresponding 2H-1,4-benzoxazin-2-ones 9a,b along with the 3H-indol-3-one 11, whereas with keto ylides 12a,b, 2,3-dihydrobenzoxazoles 13a,b were isolated. Conversely, the reaction of 1b with moderated phosphonium salt 15 proceeded under phase-transfer catalysis conditions to afford the 2H-1,4-benzoxazine derivative 19, instead of the expected Wittig reaction product.