Synthesis of novel N,N′-bis(triflyl)-1,7-dihydroimidazo[4,5-b]pyridines and their δ-bromolactone derivatives as antifungal agents

Abstract

The nucleophilic addition of bis(trimethylsilyl)ketene acetals to 1H-imidazo[4,5-b]pyridine in the presence of triflic anhydride has been examined. The reaction proceeds in a highly regioselective fashion and affords carboxylic acid 7-substituted 1,7-dihydroimidazo[4,5-b]pyridines exclusively. Subsequent reaction of these acids can be efficiently turned into novel tricyclic α-lactones by a regioselective ring closing procedure promoted by a NBS. Antifungal and anti-oomycete activity of newly synthesized compounds were performed in vitro against two phytopathogen fungi; A. alternate and F. oxysporum; and, against two phytopathogen oomycetes, P. aphanidermatum and P. capsici. Carboxylic acids were found to be more active than lactones, mainly for the inhibition of the radial growth of A. alternata.