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Internal affairs: Indoles, benzofurans, and enol lactones are formed chemoselectively from the rhodium-catalyzed cycloisomerization reaction of easily prepared alkynyl aniline substrates (see scheme, cod=cycloocta-1,5-diene, DMF=N,N-dimethylformamide). The reaction may proceed by nucleophilic capture of a vinylidene intermediate. Indoles are formed under mild conditions using low catalyst loadings.
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Trost et al. (2007) studied this question.
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