6533b874fe1ef96bd12d66d5
RESEARCH PRODUCT
The influence of substitution in the quinoxaline nucleus on 1,3-dipolar cycloaddition reactions
Antonino LauriaAnna Maria AlmericoGiampaolo Baronesubject
Settore CHIM/03 - Chimica Generale E InorganicaSettore CHIM/08 - Chimica FarmaceuticaDFT calculations 13-Dipolar cycloaddition reactions Quinoxalines Reaction mechanismdescription
The reaction mechanism of 1,3-dipolar cycloadditions of both symmetric and unsymmetric benzo-condensed diazines with a nitrilimine dipole, to give two different mono- and bis-cycloadducts, in tetrahydrofuran (THF) solution, was studied by DFT calculatio ns. The results obtained show that each 1,3-dipolar cycloaddition reaction always proceeds by a two steps mechanism, in which the first intermediate shows only one covalent bond between the beta carbon of the nitrilimine and the aromatic nitrogen of the diazine molecule. The structure and energy content of the two transition states of the two cycloaddition steps, in the case of the unsymmetric benzo-condensed diazine, nicely explains why the product of the bis-cycloaddi tions is exclusively observed and why the product of a mono-cycloaddition is not isolated for the symmetric reaction pathway.
year | journal | country | edition | language |
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2013-01-01 |