Preparation of Ketene Imines by a Beckmann Rearrangement

Abstract

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).

Synthesis, Configuration, and15N NMR Spectra of Iminoaziridines. Synthons Equivalent to Three Components of the Ugi Reaction

“…In the case of 9c and 9d , crude α-bromoimidoyl chlorides, formed from α-bromoamides and thionyl chloride, were employed as starting materials. Small amounts of ketene imines were detected by IR spectroscopy in most crude α-bromoamidines 9 . The presence of ketene imines is indicative of an elimination−addition mechanism of amidine formation.…”