3,4-Fused dihydroindoles

DihydroindolesA novel synthesis of fused dihydroindoles involves [2 + 2 + 2]cycloaddition of alkynes with the 2,3-double bond of N-alkynoylated pyrroles. The reaction of 1 with bis(trimethylsilyl)ethyne results in two diaster-... 

Transition metal-mediated routes to six-membered nitrogen rings have figured prominently this year. Vollhardt and his group have reported a novel route to the fused dihydroindoles (202) which... 

Intramolecular replacement of fluorine by nitrogen has been used for the formation of fused heterocycles, i.e. derivatives of indole,187 - 189 2,3-dihydroindole.190 benzopyrazole.191 benzo-pyridazine,192 benzoxazine,193194 bcnzothiadiazole,193 quinoline,196-198 and benzothiazinc (e.g., 9).194 1"-200... 

Flanagan also observed the formation of fused [l,2]indoles as a result of radical cyclization sequences when lV-(o-halobenzyl)indoles 149 were heated under standard tin hydride conditions [82]. However, in contrast to what was observed by Caddick and Fiumana, dihydroindoles were isolated due to quenching of the intermediate benzyl radical with tributyltin hydride, rather than rearomatization from loss of a hydrogen atom. Consequently, lV-(o-bromobenzyl)indole 149a... 

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