Abstract
AbstractTreatment of 2‐isocyanatobenzoyl chloride (4) with 5‐aminotetrazole (5‐AT) gave 3‐(5‐tetrazolyl)quinazoline‐2,4(1H,3H)‐dione (1) directly. Treatment of 2‐carbomethoxyphenyl isocyanate (5) with 5‐AT gave 2‐[((5‐amino‐1H‐tetrazol‐1‐yl)carbonyl)amino]benzoic acid methyl ester (6) as a kinetic product, which was thermally isomerized to 2‐[((1H‐tetrazol‐5‐ylamino)carbonyl)amino]benzoic acid methyl ester (7), the thermodynamically more stable urea. Cyclization of 7 with polyphosphoric acid gave 2‐(1H‐tetrazol‐5‐ylamino)‐4H‐3,1‐benzoxazin‐4‐one (2). Urea 6 was quite labile in solution, as shown by nmr, and readily reacted with methanol to give 2‐[(methoxycarbonyl)amino]benzoic acid methyl ester (10).
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