Abstract
(E)-1-(1H-Benzo[d]imidazol-2-yl)-3-(dimethylamino)prop-2-en-1-one 2 was synthesized by one-pot synthesis protocol of 2-acetyl benzo[d]imidazole with dimethylformamide dimethylacetal (DMF-DMA) in xylene at 140 degrees C for 8 h. Reaction of enaminone derivative 1 with acetylacetone in the presence of AcOH/NH4OAc under reflux afforded the cyclized pyridino-benzo[d]imidazole derivative 3. The latter compound was converted into the corresponding beta-enaminone 4 with DMF-DMA. The single crystal X-ray diffraction technique eventually confirmed the assigned chemical structure of the N-alkyl-beta-enaminone 2 and pyridino-benzo[d]imidazole derivative 3. N-alkyl-beta-enaminone 2 crystallized in the monoclinic space group P2(1)/n with unit cell parameters of a = 9.8953(3) angstrom, b = 5.7545(2) angstrom, c = 21.7891(7) angstrom, and beta =100.627(2)degrees, and with one molecule per asymmetric unit. On the other hand, compound 3 crystallized in the orthorhombic crystal system and space group P2(1)2(1)2(1) with unit cell parameters of a = 6.82950(10) angstrom, b = 8.00540(10) angstrom, c = 22.4779(2) angstrom, and also with one molecule per asymmetric unit. Based on Hirshfeld analysis, the H...H (51.3%), O...H (10.0%), N...H (10.3%), and C...H (27.6%) contacts in 2 and the H...H (46.8%), O...H (9.9%), N...H (13.0%), and C...H (21.6%) in addition to the C horizontal ellipsis C (6.7%) interactions in 3 are the most important towards crystal stability via molecular packing. The main difference is the presence of pi-pi interaction among the molecular units of 3 but not in 2. The calculated H-1 and C-13 NMR chemical shifts showed good agreements with experimental data. Electronic properties and reactivity parameters of both compounds are also calculated and compared.