MOLECULAR-STRUCTURE OF HETEROCYCLES - 2 NMR-SPECTROSCOPY, X-RAY-DIFFRACTION, AND SEMIEMPIRICAL MO CALCULATIONS OF METHOXY-4-TRICHLOROMETHYL-HEXAHYDROPYRIMIDIN-2-ONE

The structure of 5-Bromo-4,6-dimethoxy-4-(trichloromethyl)hexahydro 2- pyrimidinone (3), synthesized from the reaction of thoxy-4-(trichlorom ethyl)tetrahydro-2-pyrimidinone (2) with bromo and methanol, was deter mined by nmr spectroscopy, X-ray diffraction, and semiempirical MO cal culations. H-1 and C-13 nmr data shown that only one pair of the diast ereoisomers was obtained. The AM1 calculations showed that 3a is the m ore stable diastereoisomers pair. The x-ray diffraction data confirmed that only the structure 3a (4S5S6R/4R5R6S) of compound 3 was obtained . Compound 3a (C7H10BrCl3N2O3, M-r = 356.43) crystallizes in the ortho rhombic space group P2(1)2(1)2(1) With the unit cell dimensions a = 7. 112(2), b = 14.719(2) and c = 12.084(3) Angstrom, R = 7.32 % and wR(2) = 14.92 % for an F-2 refinement on unique data with 2931 reflections collected and 2248 independent (R-int = 4.01%), Flack parameter 0.00(3 ).