Stereoselective Cascade Double-Annulations Provide Diversely Ring-Fused Tetracyclic Benzopyrones
作者:Baburaj Baskar、Kathrin Wittstein、Muthukumar G. Sankar、Vivek Khedkar、Markus Schürmann、Kamal Kumar
DOI:10.1021/ol3028412
日期:2012.12.7
A cascade double-annulation strategy employing diverse pairs of zwitterions with 3-formylchromones is presented that provides stereoselective access to complex tetracyclic benzopyrones. Different zwitterions incorporated different rings that include aza-, oxa-, and carbocycles fused to a common benzopyrone scaffold and in the process created three contiguous chiral centers including an all-carbon-quaternary center with high efficiency and excellent stereoselectivity.
Dimethyl Sulfide Induced [3 + 2] Annulation Strategy: An Efficient Synthesis of Functionalized Dihydropyrazole Derivatives Using the Baylis−Hillman Bromides
作者:Deevi Basavaiah、Suparna Roy
DOI:10.1021/ol800424v
日期:2008.5.1
of 1,3-dipoles for cycloaddition onto dialkyl azodicarboxylates (dipolarophiles) under the influence of dimethyl sulfide and potassium carbonate to provide functionalized dihydropyrazole derivatives in a simple one-pot [3+2] annulationstrategy.