Diels-alder reactions of 2-(2-nitroethenyl)-1H-pyrroles and their oxygen and sulfur analogs with quinones

Abstract

Diels-Alder reaction of 2-(E-2-nitroethenyl)-1H-pyrrole (2a) with 1,4-benzoquinone gave the desired benzo[e]indole-6, 9(3H)-dione (4a) in 10% yield versus a 26% yield (lit. 86% [5]) of the known N-methyl compound (4b) from the N-(or 1)-methyl compound (2b). Protection of the nitrogen of 2a with a phenylsulfonyl group (2c) gave a 9% yield of the corresponding N-(or 3)-phenylsulfonyl compound (4c). The reaction of 2b with 1,4-naphthoquinone gave in 6% yield (lit. 64% [5]) the known 3-methylnaphtho[2,3-e]-indole-6, 9(3H)-dione (6). The reaction of 2-(E-2-nitroethenyl)furan (8a) gave a small yield of the desired naphtho[2,1-b]furan-6, 9-dione (9a), recognized by comparing its NMR spectrum with that of 4b. The corresponding reaction of 2-(E-2-nitroethenyl)thiophene (8b) gave a 4% yield of naphtho[2,1-b]thiophene-6,9-dione (9b), previously prepared in 24% yield [12] in a three-step procedure involving 2-ethenylthiophene. Introducing an electron-releasing 2-methyl substituent into 8a and 8b gave 12a and 12b, which, upon reaction with 1,4-benzoquinone, gave 2-methylnaphtho[2,1-b]furan-6, 9-dione (13a) and its sulfur analog (13b) in yields of 4 and 8%, respectively.

Synthesis of Heteroaryl-Substituted Pyrroles via the 1,3-Dipolar Cycloaddition of Unsymmetrical Münchnones and Nitrovinylheterocycles

“…15 N-(Phenylsulfonyl)pyrrole 22 was generated in 81% yield from 18 (Scheme 3). 16 Scheme 3 Synthesis of nitrovinylheterocycles. Reagents and conditions:…”

Crystal structure of (±)-(3aR,5R,8bR)-5-hydroperoxy-2-phenyl-6-tosyl-4,5,6,8b-tetrahydropyrrolo[3,4-e]indole-1,3(2H,3aH)-dione

“…Related reactions have been done with other heterocycles (Abarca et al, 1985;Jones et al, 1984;Noland et al, 1983). Diels-Alder reactions between vinylheterocycles and dienophiles are useful for forming fused ring systems that may have biological activity or versatility in natural product synthesis (Booth et al, 2005;Kanai et al 2005;Nagai et al 1993;Noland & Pardi, 2005).…”

A Diels–Alder/Ene Cascade Leading to 5‐(Pyrrolidin‐3‐yl)thieno[3,2‐e]isoindoles from Ketone‐derived 2‐Vinylthiophenes and N‐Phenylmaleimide

“…We previously reported Diels–Alder adducts from 3‐vinylindoles and 2‐vinylpyrroles and 3‐vinylpyrroles . Most of these examples incorporated N ‐phenylmaleimides as the dienophile component, with several showing promising pharmacological activity.…”