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Gold(I)-catalyzed [4 + 1]/[4 + 3] annulations of diazo esters with hexahydro-1,3,5-triazines: Theoretical study of mechanism and regioselectivity.
- Source :
-
Journal of Organometallic Chemistry . Oct2019, Vol. 897, p70-79. 10p. - Publication Year :
- 2019
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Abstract
- Hexahydro-1,3,5-triazines are often used as formaldimine precursors. The recent success of Sun et al. (Angew. Chem. Int. Ed., 2016, 55 , 11867) in achieving gold-catalyzed [4 + 1]/[4 + 3] annulations of hexahydro-1,3,5-triazines with diazo esters, in which the hexahydro-1,3,5-triazine is directly used as the 1,4-dipole in the annulation, represents a breakthrough in mechanistic studies. In the present work, density functional theory (DFT) calculations were used for detailed investigation of possible catalytic mechanisms. The proposed catalytic cycle involves five major stages: dinitrogen elimination to form a gold–carbene intermediate; diazoacetate–hexahydro-1,3,5-triazine C–C coupling to give an ammonium ylide; ring opening of the hexahydro-1,3,5-triazine via C–N single-bond cleavage; a second C–N single-bond cleavage; and C–C-bond-forming reductive elimination. The regioselectivities of the cycloaddition of hexahydro-1,3,5-triazines with enol diazoacetates differ from those of cycloadditions with vinyl diazoacetates. The calculations also clarified the origins of the substrate-controlled regioselectivity. Image 1 • Origin of substrate-controlled regioselectivity was clarified. • Novel reaction mechanism for the hexahydro-1,3,5-triazine was exploited. • Second gold is important in facilitating the reaction. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 0022328X
- Volume :
- 897
- Database :
- Academic Search Index
- Journal :
- Journal of Organometallic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 137703786
- Full Text :
- https://doi.org/10.1016/j.jorganchem.2019.06.032