Ab initio and density functional theory studies of peri- and regioselectivity in 1,3-dipolar cycloaddition reaction of 1,2-diazepine with nitrile oxide |
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Authors: | R Jalal M El Messaoudi M Esseffar |
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Institution: | a Département de Chimie, Faculté des Sciences et Techniques, Université Cadi ayyad, B.P. 618 Marrakesh, Morocco b Département de Chimie, Faculté des Sciences Semlalia, Université Cadi ayyad, B.P. 3809 Marrakesh, Morocco |
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Abstract: | 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-tetrazatricyclo7,3,1,02,6]trideca-3,7,11-triene is the favored product of this reaction. |
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Keywords: | 1 2-Diazepine Nitrile oxide 1 3-Dipolar cycloaddition Ab initio DFT Structure Regio- and periselectivity |
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