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DOI: 10.1039/A703187D (Paper) Reference Section for: J. Chem. Soc., Perkin Trans. 2, 1997, 1913-1918

NMR and polymorphism of a piperidinone-substituted benzopyran with a fluorinated sidechain

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Susan C. Campbell, Robin K. Harris, Martin J. Hardy, David C. Lee and David J. Busby

Abstract

Two polymorphs of (3S-trans)-1-[3,4-dihydro-3-hydroxy-2,2-dimethyl-6-(pentafluoroethyl)-2H-1-benzopyran-4-yl]piperidin-2-one (A)[hair space]‡ have been characterised by solid-state 13C and 19F cross-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, including variations in residual dipolar coupling characteristics and crystallographic splitting of resonances, indicating that more than one molecule exists in the asymmetric unit of polymorphic form II. The 13C NMR studies involved triple-channel operation, with simultaneous decoupling of 1H and 19F, including cross polarisation from 19F as well as from 1H. Dual-channel 19F measurements have been carried out using 1H decoupling, with cross polarisation from 1H.

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