Spiro heterocyclization of methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H- pyrrole-2-carboxylates by the action of diphenylguanidine

Reactions of monocyclic 1H-pyrrole-2,3-diones with guanidines were not reported. We examined reactions of methyl 1-aryl-3-aroyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates Ia and Ib with 1,3-diphenylguanidine (II) at a molar ratio of 1 : 1 in boiling anhydrous 1,2-dichloroethane (reaction time 1–2 h; TLC monitoring) and isolated 6-aryl-9-aroyl-8-hydroxy-2-imino-1,3-diphenyl-1,3,6-triazaspiro[4.4]non8-ene-4,7-diones IIIa and IIIb whose structure was confirmed by X-ray analysis. Presumably, compounds IIIa and IIIb are formed via addition of one secondary amino group in diphenylguanidine II at the C atom of pyrroledione Ia or Ib, followed by closure of imidazole ring as a result of intramolecular attack by the second secondary amino group in II on the ester carbonyl group and elimination of methanol molecule. and 1 mmol of diphenylguanidine II in 10 ml of anhydrous 1,2-di-chloroethane was heated for 1 h under reflux. The mixture was cooled, and the precipitate was filtered off. Yield 79%, mp 243–244°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3070 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1615 br (9-C=O). H NMR spectrum, δ, ppm: 2.41 s (3H, Me), 7.10–7.69 m (19H, Harom), 9.44 br.s (2H, NH, OH). Found, %: C 72.73; H 4.50; N 10.67. C32H24N4O4. Calculated, %: C 72.72; H 4.58; N 10.60. 9-(4-Ethoxybenzoyl)-8-hydroxy-2-imino-6(4-methylphenyl)-1,3-diphenyl-1,3,6-triazaspiro[4.4]non-8-ene-4,7-dione (IIIb) was synthesized in a similar way. Yield 75%, mp 251–252°C (from 1,2-dichloroethane). IR spectrum, ν, cm: 3050 br (OH, NH), 1790 (C=O), 1730, 1700 (C=O), 1610 br (9-C=O). H NMR spectrum, δ, ppm: 1.35 t (3H, CH3CH2, J = 7.0 Hz), 2.40 s (3H, Me), 4.08 q (2H, CH2O, J = 7.0 Hz), 6.85–7.81 m (18H, Harom), 9.28 br.s (2H, NH, OH). Found, %: C 71.38; H 4.88; N 9.70. C34H28N4O5. Calculated, %: C 71.32; H 4.93; N 9.78. The IR spectra were recorded on an FMS-1201 spectrometer from samples dispersed in mineral oil. The H NMR spectra were measured on a Bruker WP400 instrument from solutions in DMSO-d6 using tetramethylsilane as internal reference. The purity of the products was checked by TLC on Silufol plates using ethyl acetate as eluent; spots were visualized by treatment with iodine vapor. This study was performed under financial support by the Russian Foundation for Basic Research (project no. 07-03-96 036). Ar = Ph (a), 4-EtOC6H4 (b). ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 12, p. 1891. © Pleiades Publishing, Ltd., 2010. Original Russian Text © N.V. Bubnov, E.S. Denislamova, Z.G. Aliev, A.N. Maslivets, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 12, p. 1876.