us to attempt the synthesis of N-phenylnaphtho[2,3-b]azetinone (2). When a solution of 3-phenyl-3,4-dihydronaphtho[2,3-d]-1,2,3-triazin-4-one (3) [m.p. 226 'C, UV in CH2C12: 365 nm (E = 6800); 348 nm (E = SSOO), 265 nm (E = 44500). 246 nm (E = 28300); I R (KBr): CO at 1700 cm-11 in tetrahydrofuran is irradiated under a high-pressure mercury-vapor lamp (450 W, Hanovia) one equivalent of nitrogen is evolved with formation of N-phenyInaphtho[2,3-b]azetinone (2) and benzo[d]acridone ( 6 ) . After chromatographic working-up (silica gel, CH2C12) these compounds are isolated in yields of 92 % and 5 % respectively. 0 13) (41 Compound ( 2 ) is recrystallized from ether as golden-yellow rods, m.p. 155 ' C , mol. wt. (osmometric) 245.8, (mass spectrometric) 245, UV (in CH2C12): 394 nm (c = 2000), 276.5 nm (E = SZOOO), 232 nm (E = 36000). The p-lactam structure follows from the IR spectrum, in which a CO band appears at 1805 cm-1 in KBr (1815 cm-1 in CHZC12); it is remarkable that this band is shifted ca. 60 cm-1 to higher wavenumbers than is the corresponding CO band in the spectrum of 1,4-diphenyl-3-azetin-2-one [41. The N M R spectrum of (2) shows a multiplet of aromatic protons between T = 2.2 and 3.1 (CDCI3); one proton, possibly the C-8 one, shows a greater upfield shift than the others and appears at T = 3.07. In this region the spectrum of (2) resembles that of methyl 3-amino-2-naphthoate. If compound (2) is boiled in methanol or heated in morpholine, the well known methyl 3-phenylamino-2-naphthoate or the morpholide, m.p. 155-156'C, is obtained. The diazonium intermediate ( 4 ) probably occurs [51 during the formation of (2) from ( 3 ) ; (6) is formed from (2) by valence isomerization to the non-isolable ketene ( 5 ) 161 and subsequent cyclization. We have obtained evidence for this reaction course by photolyzing compound (2). from which we obtained (6).

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