Structural modifications leading to changes in supramolecular aggregation of thiazolo[3, 2-a]pyrimidines: Insights into their conformational features
作者:H NAGARAJAIAH、NOOR SHAHINA BEGUM
DOI:10.1007/s12039-014-0694-9
日期:2014.9
The compounds, 7-methyl-3,5-diphenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester (1), 3-amino-2-cyano-7-methyl-5-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid methyl ester (2), 2-dimethylaminomethylene-7-methyl-3-oxo-5-phenyl-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester (3), 2-(3-cyano-benzylidene)-5-(4-hydroxy-phenyl)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid methyl ester; with N,N-dimethyl-formamide (4) and 3-ethoxycarbonylmethyl-5-(4-hydroxy-3-methoxy-phenyl)-7-methyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid methyl ester (5) have been synthesized and their structures evaluated crystallographically. Compound 1 crystallizes in the space group Pı̄ with Z=8, with four molecules in the asymmetric unit. Compound 2 also crystallizes in the space group Pı̄ with Z=4 wherein asymmetric unit accommodates two molecules. Compound 3 belongs to P21/c with Z=4, compound 4 crystallizes in Pbc2 1 with Z=4 and compound 5 belongs to Pı̄ with Z=2. In all the above compounds, the aryl ring positioned at C5 of thiazolopyrimidine ring is almost perpendicular. In the case of compounds with substituted phenyl ring, aryl group-up conformation predominates. However, for compounds with unsubstituted phenyl ring, aryl group-down conformation is adopted. By varying the substituents at positions C2, C3, C6 and on the aryl at C5 in the main molecular scaffold of (1-5), we have observed significant differences in the intermolecular interaction patterns. The packing features of the compounds are controlled by C-H…O, C-H…N, N-H…N O-H…N, C-H…π and π…π weak interactions.
化合物7-甲基-3,5-二苯基-5H-噻唑并[3,2-a]嘧啶-6-羧酸乙酯(1)、3-氨基-2-氰基-7-甲基-5-苯基-5H-噻唑并[3,2-a]嘧啶-6-羧酸甲酯(2)、2-二甲氨基亚甲基-7-甲基-3-氧代-5-苯基-2,3-二氢-5H-噻唑并[3,2-a]嘧啶-6-羧酸乙酯(3)、2-(3-氰基-亚苄基)-5-(4-羟基-苯基)-7-甲基-3-氧代-2,3-二氢-5H-噻唑并[3,2-a]嘧啶-6-羧酸甲酯;与N,N-二甲基-甲酰胺(4)和3-乙氧羰甲基-5-(4-羟基-3-甲氧基-苯基)-7-甲基-5H-噻唑并[3,2-a]嘧啶-6-羧酸甲酯(5)已被合成,并通过晶体学评估了它们的结构。化合物1在空间群Pı̄中结晶,Z=8,不对称单元中有四个分子。化合物2也在空间群Pı̄中结晶,Z=4,不对称单元容纳两个分子。化合物3属于P21/c,Z=4,化合物4在Pbc2 1中结晶,Z=4,化合物5属于Pı̄,Z=2。在所有上述化合物中,位于噻唑并嘧啶环C5位置的芳基环几乎垂直。对于具有取代苯环的化合物,芳基向上构象占主导地位。然而,对于具有未取代苯环的化合物,采用芳基向下构象。通过在(1-5)的主分子骨架的C2、C3、C6位置和C5的芳基上变化取代基,我们观察到了分子间相互作用模式的显著差异。化合物的堆积特征受C-H…O、C-H…N、N-H…N、O-H…N、C-H…π和π…π弱相互作用的控制。