Phosphono‐substituted isoindolines and indoles from 2,3‐ and 2,4‐benzoxazin‐1‐ones

Reactions of 2,3‐benzoxazinone 1 and 2,4‐benzoxazinone 2, with trialkyl phosphites 3a–c provide access to new phosphono‐substituted isoindolines 6a–f and indoles 19a–e, respectively. Phosphono‐substituted 2,3‐benzoxazines 5a–c were also obtained in the first reaction. Bisisoindolinylidene (7) was, however, isolated in low yields when 1 was heated with triethyl or triisopropyl phosphite at 100deg;C whereas at 170deg;C 7 was obtained as the major product (∼53%). On the other hand, the reaction of 1 or 2 with dialkyl phosphonates 4a–c proceeded in the presence of aqueous solution of NaOH (5%) to give the respective alkylated product 14a–c or 20a–c.