A novel and efficient synthesis of 4H-3,1-benzoxazines by a tandem aza-Wittig/heterocumulene-mediated annulation strategy

Article abstract of DOI:10.1055/s-1991-26368

2-[(Triphenylphosphoranylidene)amino]benzyl alcohol 2 reacts with isocyanates or isothiocyanates in refluxing toluene to give the corresponding 2-alkyl(aryl)amino-4H-3,1-benzoxazines 5. Iminophosphorane 2 also reacts with carbon dioxide and carbon disulfide to give 4H-3,1-benzoxazin-2(1H)-one (6) and -thione (7), respectively.