Structural studies in azolylmethanes

The crystal structures of a number of fungicidal azolylmethanes are compared. In the benzyl compounds [1-aryl-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ones, the corresponding pentan-3-ols, and 1-(4-chlorophenyl)-3-(2-fluorophenyl)-2-(1,2,4-triazol-1-yl)propan-1-one], the benzyl and tert-butyl groups (or 4-chlorophenyl group) are trans, whereas in the analogous phenoxy compounds [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)butan-2-one and the corresponding butan-2-ol], the tert-butyl groups are trans to the triazole and gauche to the phenoxy group. Coupling constants, determined by nuclear magnetic resonance (n.m.r.) spectroscopy, suggest that for some compounds there is one dominant solution conformation. Intramolecular hydrogen bonding, observed by infrared spectroscopy in two of the compounds, supports the findings by n.m.r. For some compounds, the crystal and solution conformations appear to be very similar, whereas in others they are quite different. Published data on the relative activity of the enantiomers of the benzyl- and phenoxy-compounds are discussed, but differences in the relative activity of enantiomers in the two series cannot be readily rationalised. It is concluded that different enantiomers may have different modes of binding at the active site.