A chiral N-heterocyclic carbene (NHC)-catalyzed [4 + 2] annulation of γ-chloroenals and α-arylidene pyrazolinones was developed in the absence of expensive oxidants. The reaction proceeds smoothly via a vinyl enolate intermediate to afford spirocyclohexane pyrazolones in moderate to good yield (up to 86%) with high diastereoselectivities (up to 15:1 dr) and excellent enantioselectivities (up to >99%
Enantioselective aminocatalytic synthesis of tetrahydropyrano[2,3-c]pyrazoles via a domino Michael-hemiacetalization reaction with alkylidene pyrazolones
作者:Rajendra Maity、Subhas Chandra Pan
DOI:10.1039/c7ob02170d
日期:——
An enantioselectiveorganocatalytic domino Michael-hemiacetalization reaction between alkylidene pyrazolones and cyclic ketones/pentanal has been revealed. The fused tetrahydropyranopyrazole products having three contiguous stereocentres were obtained with perfect diastereoselectivities and in moderate to good yields with good to high enantioselectivities. Also, few synthetic transformations of the
Highly Diastereo- and Enantioselective Synthesis of Spiro-tetrahydrofuran-pyrazolones via Organocatalytic Cascade Reaction between γ-Hydroxyenones and Unsaturated Pyrazolones
作者:Buddhadeb Mondal、Rajendra Maity、Subhas Chandra Pan
DOI:10.1021/acs.joc.8b00781
日期:2018.8.3
The first diastereo- and enantioselective synthesis of spiro-tetrahydrofuran-pyrazolones is reported via organocatalytic asymmetric cascade oxa-Michael/Michael reaction between γ-hydroxyenones and unsaturated pyrazolones. Bifunctional squaramide catalyst was found to be effective for this reaction. With 10 mol % of catalyst, excellent results were attained for a variety of spiropyrazolones under mild