2-[3-(Trifluoromethyl)phenyl]furo[3,2-b]pyrroles: synthesis and reactions

The synthesis and reactions of methyl 2-3-(trifluoromethyl)phenyl]-4H-furo3,2-b]pyrrole-5-carboxylate (1a) are described. Upon reaction with methyl iodide, benzyl chloride, or acetic anhydride, this compound gave N-substituted products 1b-d. By hydrolysis of compounds 1a-c, the corresponding acids 2a-c were formed, or by reaction with hydrazine-hydrate, the corresponding carbohydrazides 3a-c were formed. By heating 2-3-(trifluoromethyl)phenly]-4H-furo3,2-b]pyrrole-5-carboxylic acid (2a) in acetic anhydride, 4-acetyl-2-3-(trifluoromethyl)phenyl]furo3,2-b]pyrrole (4) was formed. By hydrolysis of 4, 2-3-(trifluoromethyl)phenyl]-4H-furo3,2-b]pyrrole (5a) was formed, and reactions with methyl iodide or benzyl chloride gave N-substituted products 5b-c. The reaction of 4 with dimethyl butynedioate gave substituted benzob]furan 6. Compound 3a reacted with triethyl orthoesters giving 7a-c, which afforded with phosphorus (V) sulphide the corresponding thiones 8a-c. The thiones 8a-c reacted with hydrazine hydrate to form hydrazine derivatives 9a-c. The reaction of triethyl orthoformiate with compounds 9a-c led to furo2′,3′: 4,5]pyrrolo1,2-d]1,2,4]triazolo3,4-f]1,2,4]triazines 10a-c. Hydrazones 11a-c were formed from 3a-c and 5-3-(trifluoromethyl)phenyl]furan-2-carboxaldehyde. The effect of microwave irradiation on some condensation reactions was compared with “classical” conditions. The results showed that microwave irradiation shortens the reaction time while affording comparable yields.