Perkin communications. Ready alcoholysis of the cycloadducts (urazole) of 4-phenyl-1,2,4-triazole-3,5-dione by solvent-assisted backbone participation

摘要

J. CHEM. SOC. PERKIN TRANS. I 1991 Perkin Communications Ready Alcoholysis of the Cycloadducts (Urazole) of 4-Phenyl-1,2,4-triazole-3,5-dione by Solvent-assisted Backbone Participation Kazuyoshi Seguchi * and Satoko Tanaka Faculty of Home Science, Mukogawa Women's University, 6-46 lkebiraki- cho, Nishinomiya 663,Japan A series of urazoles containing ap-carbonyl groups underwent ready alcoholysis by solvent-assisted backbone participation in the presence of potassium hydroxide to give oxazolinones. Although 4-phenyl-1,2,4-triazole-3,5-dione(PTAD) shows a diversity of reactions with alkenes, e.g. 4 + 2,',, 2 + 2,, ene,3*4 and dipolar reaction^,^ to afford unique adducts (urazole), use of the latter has been This is probably because the urazole ring is difficult to open and relatively drastic conditions are needed to accomplish it (e.g.KOH in refluxing MeOH' or PriOH);9 hydrazine in ethanol has, however, been recommended for the mild hydrolysis of strained urazoles. lo Here, we report that the urazoles arising from the reaction of a variety of styryl ketones with PTAD,' were readily cleaved by solvent-assisted participation of the neighbouring p-car- bony1 group (backbone participation) under mild conditions to give new bicyclic oxazolinones. As reported previously,' benzylideneacetone la reacted with PTAD to give 2a (27) via an addition-elimination mechanism. Treatment of an ethanolic solution of 2a with powdered KOH for 30 min at 25 "C, resulted in loss of the characteristic colour.Work-up of the solution (neutralization by dilute HCI and recrystallization from EtOH), gave white needles of 3a (77). The oxazolinone structure was assigned on the basis of spectral evidence: 6, 1.72, 5.35 and 6.54 Me, olefinic (5-H), and amide protons in addition to ethoxy protons; 6, 79.7 (d, C-5) and 154.0 and 154.5 (both s, CONH,). The mass and the IR spectra and elemental analyses supported the proposed structure. It is suggested that the facile ring-opening under mild conditions proceeds by solvent- assisted participation of a neighbouring and enolizable carbonyl group (see Scheme 1). Similar reactions (see Table 1) gave a series of oxazolinones the structures of which were also assigned on the basis of the elemental analyses and spectral evidence.Starting material was, however, recovered for entry 4, presumably because of the low nucleophilicity and steric bulkiness of the tert-butoxy group. Experimental Synthesis of the Oxazolinone 3a.-To a suspension of compound 2a (164 mg, 0.50 mmol) in ethanol (20 ml) was added powdered potassium hydroxide (200 mg, 3.6 mmol). The solution was stirred (magnetic stirrer) for 30 min at 25 "C during which time the characteristic yellow colour disappeared. The solution was diluted with water (50 ml) and neutralized by hydrochloric acid (2 mol drn-,) to give a white precipitate. This was filtered off by suction and recrystallized (ethanol) to give 3a (77O/,)as colourless needles; m.p. 109-1 10 "C; 6,(60 MHz; CDCI,) 1.41 (3 H, t, CH3), 1.72 (3 H, s, CH,), 3.80 (2 H, q, CH,), 5.35 (1 H, s, 5-H), 6.54 (1 H, s, NH) and 7.08-7.54 (9 H, m, Ph); 6,(200 MHz; CDCI,) 15.4(q), 21.0(q), 68.l(t), 79.7(d), 86.1(s), 96.9(s), 116.3(d), 125.2(d), 125.3(d), 127.7(d), 128.2(d), 129.2(d).129.9(s), 130.7(d), 133.9(d), 139.3(s), 154.9(s) and 154.5(s); bsol;.mJx(KBr)/cm-' 3320, 1763, 1712, 1610, 1124 and X 0 1 PTAD 2 a X=H,R=Me b X=H,R=Ph R'OHIKOH c X=OMe,R=Me I X 0 X 9 -Ph :OR' R' d 3 R'= Me Et Pr' Bur Scheme 1 Alcoholysis of urazole with backbone participation Table 1 Preparation of oxazolinones 3 by backbone participation Entry X R 1 H Me 2 H Me 3 H Me 4 H Me 5 H Ph 6 H Ph 7 OMe Me Based on 2. R' Yield of3()" Me 76 Et 77 Pr' 23 Bu' 0 Et 65 Pr' 60 Et 50 1104; m/z () 365 (100, M'), 321 (30), 276 (36), 200 (24) and 158 (14) (Found: C, 65.9; H, 5.16; N, 11.6.C,,H19N,04 requires C, 65.72; H, 5.24; N, 11.51). References 1 R. C. Cookson, S. S. H. Giliani and I. D. R. Stevens, J. Chem. Soc. C, 1967, 1905. 2 W. Adam, V. Lucchini, E.-M. Peters, L. Pasquato, H. G. Schnering, K. Seguchi, H. Walter and B. Will, Chem. Ber., 1989, 122. 133. 3 C.-C.Cheng, C. A. Seymour, M. A. Petti and F. D. Greene, J. Org. Chem., 1984,49, 29 10. 4 A. LaPorterie, J. Dubac, G. Manuel, G. Deleris, J. Kowalski, J. Dunogues and R. Calas, Terruhedron, 1978, 34, 2669. 2884 J. CHEM. SOC. PERKIN TRANS. I 1991 5 W. Adam, 0.De Lucchi and K. Hill, Chem. Ber., 1980,102,6384. 10 W. Adam, L. A. Arias and 0.De Lucchi, Sjwthesis, 1981, 543. 6 W. Adam and 0.De Lucchi, Angew. Chem., Int. Ed. Engl., 1980, 19, 11 K. Seguchi and S. Tanaka, J. Chrm. Soc., Chem. Commun., 1991,89. 762. 7 E. J. Corey and B. B. Snider, Tetrahedron Lett., 1973,3091. 8 D. H. R. Barton, T. Shioiri and D. A. Widdowson, J. Chem. Soc., Chem. Commun., 1970,939. Paper 1/046 15 B 9 W. Adam, 0.De Lucchi and I. Erden, J. Am. Chem. Soc., 1980,102, Receiued 4th September 1991 4806. Accepted 4th September 1991