Dimers of solid 4-arylhexahydro-1H,3H-pyrido[1,2-c] pyrimidine-1,3-diones. 13C CP/MAS NMR, x-ray diffraction and semi-empirical MO studies

✍ Scribed by Franciszek Herold; Dorota Maciejewska; Irena Wolska

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 120 KB
• Volume: 13
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(200004)13:4<213::aid-poc233>3.0.co;2-#

✦ Synopsis

13
C cross-polarization magic angle spinning NMR data are reported for eight derivatives of 4-arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine-1,3-diones 1-8 and the x-ray diffraction data for 4 with R = 4'-Me. The crystal structure of 4 shows the formation of centrosymmetric dimers via intermolecular hydrogen bonds with an N2 Á Á ÁO11 distance of 2.797(3) A ˚. Deshielding of carbonyl carbons in the solids 1-8 as compared with solution shows that such dimers probably also exist in other compounds. According to the PM3 calculations, three types of dimers with two C1=OÁ Á ÁHN, two C3=OÁ Á ÁHN bonds and 'mixed,' i.e. with one C1=OÁ Á ÁHN and one C3=OÁ Á ÁHN bond, are possible.