Solid-state structure determination and solution-state NMR characterization of the (2 R,4 R)/(2 S,4 S)- and (2 R,4 S)/(2 S,4 R)-diastereomers of the agricultural fungicide propiconazole, the (2 R,4 S)/(2 S,4 R)-symmetrical triazole constitutional isomer, and a ditriazole analogue

Single-crystal X-ray diffraction analysis was used to determine the structure of a racemic diastereomer of the agricultural fungicide propiconazole [1-(2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole] and of two by-products (a symmetrical 1,3,4-triazole racemic-constitutional isomer and a propiconazole ditriazole analogue). All three crystalline racemic-diastereomers had (2 R,4 S)/(2 S,4 R)-stereochemistry in which the n-propyl group was observed in a trans-to-phenyl disposition. Propiconazole (2 R,4 S)/(2 S,4 R)-diastereomer gives crystals belonging to the monoclinic space group P2₁,/a, and, at 293 K, a=8.1192(3), b=18.9769(6), c=10.7137(4) å, Β=99.765(3){o script}, V=1626.8(1) å³, Z=4, R(F)=0.060, and R_w(F)=0.058. The constitutional isomer by-product (2 R,4 S)/(2 S,4 R)-1-(2-(2,4-dichlorophenyl)-4-n-pro-pyl-1,3-dioxolane-2-yl-methyl)-1-H-1,3,4-triazole gives crystals belonging to the monoclinic space group P2₁/n, and, at 293 K, a=11.1763(6), b=10.7716(4), c=14.5804(8) å, Β=107.445(4){o script}, V=1674.6(1) å³, Z=4, R(F)=0.043, and R_w(F)=0.043. The ditriazole byproduct (2 R,4 S)/(2 S,4 R)-1-(2-(2-chloro-4-(1,2,4-triazole-1-yl)phenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole gives crystals belonging to the triclinic space group P- 1, and, at 193 K, a=5.3329(8), b=8.3738(7), c=20.240(2) å, α=84.213(6){o script}, Β=87.20(1){o script}, γ=86.23(1){o script}, V=896.5(2) å³, Z=2, R(F)=0.046, and R_w(F)=0.051. The presence of both propiconazole (2 R.4 S)- and (2 S,4 R)-enantiomers enables the formation of a crystalline racemic modification, while the diastereomeric propiconazole (2 R,4 R)- and (2 S,4 S)-enantiomers are viscous oils. In the absence of its enantiomorphic partner, the propiconazole (2 R,4 S)- or (2 S,4 R)-enantiomers remain as viscous oils rather than form chiral crystals.