A Highly Efficient and Stereoselective Cycloaddition of Nitrones to N-Vinylpyrroles

A highly efficient [3+2] cycloaddition of nitrile oxides and azomethine imines to N-vinylpyrroles

“…2a However, despite the fact that the chemistry of N-vinylpyrroles is widely investigated, 5 the only example of a 1,3-dipolar cycloaddition involving C=C double bond is the reaction with nitrones. 6 It should be noted that reactions of Nvinylpyrroles with nitrile oxides and azomethine imines have not been studied yet. In the present work we considered the reaction of substituted N-vinylpyrroles with nitrile oxides and azomethine imines aiming the development of synthetic strategies for the preparation of pyrrolyl-isoxazoles and pyrrolyl-pyrazole ensembles.…”

“…Yield 54% (182 mg), white solid, m.p. 156-158 °C; R f (15% EtOAc/hexane) 0.31; ν max (KBr) 2935, 2923, 1477, 1404, 1336, 1352, 1301, 1206, 1094, 991, 882 s, 827 s, 799, 730 cm -1 ; δ H (400 MHz, CDCl 3 ): 7.68 (2Н, d, J 8.6 Hz, Ph), 7.45 (2Н, d, J 8 6. Hz, Ph), 6.52 (1Н, d, J 3.0 Hz, pyrrole), 6.46 (1Н, dd, J 9.9, 4.1 Hz, СН 2 СН), 6.00 (1Н, d, J 3.0 Hz, pyrrole), 3.75 (1Н, dd, J 17.7, 9.9 Hz, СН 2 СН), 3.57 (1Н, dd, J 17.7, 4.1 Hz, СН 2 СН), 2.72-2.56 (2H, m, CH 2 ), 2.56-2.46 (2H, m, CH 2 ), 1.92-1.82 (2H, m, CH 2 ), 1.81-1.72 (2H, m, CH 2 ); δ C…”

Regio- and stereoselective cycloaddition of nitrones to 1-vinyl-4,5-dihydro-1H-benzo[g]indole

“…Pyrrole and its derivatives also are important structural fragments of various natural compounds, e.g., chlorophyll, porphyrins, vitamin В 12 , and a number of others [5]. Lately efficient procedures were developed for the synthesis of compounds containing ensembles of pyrrole and imidazole [6], tetrahydroindole and triazole [7], pyrrole and isoxazolidine rings [8].We report here on the study of the process occurring between 1-vinyl-4,5-dihydro-1Н-benzo[g]-indole 1, easily obtained by Trofimov reaction [9][10][11], and nitrones of diverse structures: aldonitrones, C,Ndiaryl-(2a and 2b); N-aryl-С-carbamoylnitrones (2c and 2d), and ketonitrones, N-aryl-С,С-bis-(methoxycarbonyl)nitrones (2e and 2f). The heating for 4-19 h in toluene at 110°С furnished with a high regio-and stereoselectivity an adduct of 1,3-dipolar cycloadditon of nitrones to the vinyl group of indole 3a-3f.…”

“…Pyrrole and its derivatives also are important structural fragments of various natural compounds, e.g., chlorophyll, porphyrins, vitamin В 12 , and a number of others [5]. Lately efficient procedures were developed for the synthesis of compounds containing ensembles of pyrrole and imidazole [6], tetrahydroindole and triazole [7], pyrrole and isoxazolidine rings [8].…”

“…compounds 3a-3d was established from the comparison of the chemical shifts and spin-spin coupling constants with the data formerly obtained for nitrone adducts with substituted N-vinylpyrroles [8].…”