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The first systematic study of all dipolarophile sites of 1,2-diazepine towards nitrile oxide as dipole via 1,3-dipolar cycloaddition reactions has been carried out. To this end, the structural and energetic aspects of seventy-two isomers were determined by means of ab initio and density functional theory methods at different levels of accuracy were performed on all peri- and regio-isomeric forms. The agreement between the calculated and the experimental geometries, regio- and periselectivity of the studied reaction is good in all instances. The dipole condensation with the norcaradiene dipolarophile has been considered seemingly for the first time. The bis-cycloadduct 3a,3b,7,10a-tetrahydro-10 H-[1,2] oxazolo [4,5-d] [1,2,4] oxadiazolo [4,5-b] [1,2] diazepine is the most stable one as predicted by all methods used in this work. However, the tautomerization study of all forms of 1,2-diazepine seems to rule out the existence of the tautomeric form that provides the above mentioned cycloadduct. Consequently, the bis-cycloadduct 5,10-dioxa-1,2,4,11-tetrazatricyclo[7,3,1,02,6]trideca-3,7,11-triene is the favored product of this reaction. 相似文献
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Jalal Hassan Gholam-Reza Shams Hossein Meighani 《Journal of Analytical Chemistry》2015,70(12):1495-1500
35.
Jalal Basiri Parsa Mahdieh Farshbaf Haghro 《The Journal of chemical thermodynamics》2008,40(5):782-788
In this work, density and viscosity have been determined for (polyethylene glycol dimethyl ether 250 + 1,2-propanediol, or 1,2-butanediol, or 1,2-pentanediol, or 1,2-hexanediol) binary systems over the whole concentration range at temperatures of (293.15, 303.15, 313.15, 323.15) K and atmospheric pressure. Experimental data of mixtures were used to calculate the excess molar volumes VE, and viscosity deviations Δη. These results were fitted by the Redlich–Kister polynomial relation to obtain the coefficients and standard deviations. 相似文献
36.
The morphological structure of membranes prepared from two nearly similar systems consisting of water/N,N-dimethylacetamide (DMAc)/polyethersulfone (PES) and water/N-methyl-2-pyrrolidone (NMP)/polyethersulfone (PES) has been studied. The morphology of the prepared membranes showed that both systems exhibit an instantaneous liquid–liquid demixing that leads to the formation of macrovoids in the resulting structures. Nevertheless, the resulting macrovoid structures were contrary to the generally accepted concepts concerning macrovoid formation. The membranes morphologies showed that in spite of better miscibility between water and DMAc, which must promote the formation of channel- and finger-like structures, more sponge-like structures were observed in membranes prepared from the water/DMAc/PES system compared to those prepared from the water/NMP/PES system. To find the source of this unexpected phenomenon, the complete ternary phase diagrams consisting of theoretical binodal curves, vitrification boundaries, and gelation boundaries were constructed for both systems and it was shown that gelation process occurs earlier in the water/DMAc/PES system compared to the other system, which inhibits the growth of macrovoids in this system. 相似文献
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In this work, we study the persistence of a homoclinic orbit of the sine‐Gordon equation under diffusive and driven perturbations. An analytic perturbation method based on time‐dependent scattering theory, together with Fredholm theory, is used to establish persistence. The estimates are given in space‐time function spaces, with a certain time decay required for the existence of a homoclinic orbit. © 2000 John Wiley & Sons, Inc. 相似文献
39.
The reaction of nitrilimine 6a with ethyl pyridine-2-acetate (7) gave the corresponding pyrrolo[1,2-a]pyridine 8, while the reaction of 6b containing an ester moiety afforded the acyclic adduct 9. The reaction of 6a with 2-aminopyrimidine (10) gave the novel unexpected pyrimido[2,1-d]1,2,3,5-tetrazine 11. Acyclic adducts 16 and 17 were obtained from the reaction of 6b with 2-cyanomethylbenzimidazole (14) and 2-aminobenzimidazole (15), respectively. 相似文献
40.