provided evidence that this one‐pot synthesis proceeds through at least twelve consecutive transformations and includes at least nine different chemical reactions, making it the longest cascade reaction sequence known to date. We describe the scope and limitations of the cascadesynthesisapproaches and the development of an enantioselectively catalyzed centrocountin synthesis.
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.