Allenes. Part 34. Reactions of methylindoles and 2,5-dimethylpyrrole with allenic carbenes

Abstract

Bromoallenes give allenic carbenes under basic conditions, which react with methylindoles to give alkenylquinolines by ring expansion and alkynyl-and allenyl-3H-indoles. Under the same conditions 2.5-dimethylpyrrole is converted into a 3-al kenyl-2,6-dimethylpyridine.

Reaction of dimethylvinylidene carbene with methylpyrroles

“…(3) allenic carbenes to alkenes to give cyclopropanes is well known, and their reactions with oxygen heterocycle^,^ indoles, and 2,5dimethylpyrrole (12)4 have been investigated. In this study pyrrole (4) and a selection of methylated pyrroles were treated with dimethylvinylidene carbene (2), generated from 3-chloro-3methylbut-1-yne (1) by a phase-transfer catalytic method, and the resulting basic products were isolated chromatographically, and identified spectroscopically as 3-vinylpyridines and 2Hpyrroles; products and isolated yields are indicated in Table 1.…”

Reaction of (dimethylvinylidene)carbene with indole-3-carbaldehyde and its application in the synthesis of β-(dehydroprenyl)indole-based natural products

“…The cyclopropanation of nucleophilic olefins with (dimethylvinylidene)carbene 1, generated by the elimination of hydrogen halide from propargyl halides or halloallenes (Scheme 1), represents an important carbon-carbon bond-forming process, involving introduction of a dehydroprenyl group into organic substrates, [1][2][3][4][5][6] and has found use in natural product synthesis. 7,8 Interaction of 1 with indole itself 9 and a-and/or b-methyl indoles has been studied, 10 however, reaction between 1 and indoles containing an electron-withdrawing group at C-2 or C-3 has not been investigated. In connection with our previous studies on the regioselectivity of 1 towards different olefins 11 and synthesis of b-(dehydroprenyl)indoles, 12 we have investi-gated the reaction of 1 with indole-3-carbaldehyde.…”