Pyrroles benzannelation

The parent pyrrolopyrroles (la-lc X = Y = NR) have also not been investigated. Thienopyrroles (la-lc X = S, Y = NR) as well as their benzannelated derivatives have been investigated much more than other analogous mixed azaheteropentalenes. This is probably due to the fact that thieno-[2,3-6]- and -[3,2-6]-pyrrole derivatives are readily available... 

Dibenzannelated thieno[3,2-6 ]pyrrole (198) was also made by the action of triethyl phosphite on either of the two nitro compounds (197) and (199 Scheme 72) (71CC203, 72JCS(P1)2023). Benzannelated derivatives of thieno[2,3-6]pyrrole and thieno[3,2-6]pyrrole (200) and (201) were made likewise. Thermolysis of either azide (202) or (203) in diglyme also led to the formation of (198), presumably via nitrene intermediates (Scheme 73) <78AHC(22)183>. 

Donskaya OV, Dolgushin GV, Lopyrev VA (2002) Vicarious nucleophilic substitution of hydrogen in nitro-substituted pyrroles, azoles, and benzannelated systems based on them. Chem Heterocycl Comp 38 371-384... 

Benzannelation of 2-substituted thiophenes, benzothiophenes, pyrroles, benzofurans, and indoles has been reported with the IPr ligand (l,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene) on gold(I) (Scheme... 

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