Substituted pyrroles 3-diphenyl

If the nitrogen atom of the pyrrole ring was substituted, then pyrrolo[2, 3-6]pyridinecarboxylates (1097) were obtained in 68-74% yields on the thermal cyclization of (V-(l-substituted 2-pyrrolyl)aminomethyIenemalo-nates (1096) by heating in diphenyl ether at 250°C for 20 min [75JCS(P1)1910 89JHC1029]. 

Much work in the review period has concerned enantioselective substitution in five-membered heterocyclics. The enantioselective alkylation of some pyrroles by unsaturated 2-acylimidazoles catalysed by the bis(oxazolinyl)pyridine-scandium(in) triflate complex (31) has been reported.39 Compound (33) is formed in 98% yield and 94% ee from the 2-acylimidazole (32) and pyrrole at —40 °C. A series of enantiomer- ically pure aziridin-2-ylmethanols has been tested as catalysts in the alkylation of /V-mclhylpyrrolc and (V-methylindole by ,/l-unsalura(cd aldehydes.40 Enantiomeric excesses of up to 75% were observed for the alkylation of /V-mcthylpyrrole by ( >crotonaldehyde using (2.S ,3.S )-3-mclhylazirin-2-yl(diphenyl)methanol TFA salt as catalyst to form (34). 

Dilithio-l,3-dienes 1 could react with diaryl diazomethanes to give multi-substituted 1-imino-pyrrole or indole derivatives 46 in high yields [73]. In this reaction, diaryl diazomethanes reacted as electrophiles. Besides, synthetic methods for Af-imino-pyrrole and indole derivatives are limited. Only when 2,3-cyclic-1,4-diphenyl-1,4-dilithio-l, 3-butadiene 1 were treated with 2.2 equivalents of... 

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