NMR AND POLYMORPHISM OF A PIPERIDINONE-SUBSTITUTED BENZOPYRAN WITH A FLUORINATED SIDE-CHAIN

Two polymorphs of afluoroethyl)-2H-1-benzopyran-4-yl]piperidin-2-one ( A)double dagger have-been characterised by solid-state C-13 and F-19 c ross-polarisation magic-angle spinning NMR, aided by IR spectroscopy, differential scanning calorimetry and X-ray powder diffraction methods . The two polymorphs show markedly different NMR spectral phenomena, i ncluding variations in residual dipolar coupling characteristics and c rystallographic splitting of resonances, indicating that more than one molecule exists in the asymmetric unit of polymorphic form II. The C- 13 NMR studies involved triple-channel operation, with simultaneous de coupling of H-1 and F-19, including cross polarisation from F-19 as we ll as from H-1. Dual-channel F-19 measurements have been carried out u sing H-1 decoupling, with cross polarisation from H-1.