Reactivity of the Mitsunobu reagent toward 3-formylchromones: a strategy for the one-pot synthesis of chromeno[2,3-c]pyrazolines and chromeno[2,3-e]tetrazepines
摘要:
The zwitterionic intermediates generated from dialkyl azodicarboxylates and triphenylphosphine displayed excellent reactivity toward 3-formylchromones to afford chromeno[2,3-c]pyrazolines and chromeno[2,3-e]tetrazepines. (C) 2011 Elsevier Ltd. All rights reserved.
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.