Selva, Verónica, Selva, Elisabet, Merino, Pedro, Nájera, Carmen, Sansano, Jose M.
Sequential Metal-Free Thermal 1,3-Dipolar Cycloaddition of Unactivated Azomethine Ylides
Organic Letters. 2018, 20(12): 3522-3526. doi:10.1021/acs.orglett.8b01292
URI: http://hdl.handle.net/10045/77171
DOI: 10.1021/acs.orglett.8b01292
ISSN: 1523-7060 (Print)
Abstract: 
The thermal 1,3-dipolar cycloaddition of unactivated azomethine ylides derived from allylamine and aromatic or heteroaromatic aldehydes with maleimides and 1,1- and 1,2-bis(phenylsulfonyl)ethylene affords endo-2,5-trans cycloadducts in moderate to good yields. DFT calculations provide evidence that the diastereoselectivity observed depends on the isomerization between S- and W-ylides according to Curtin-Hammett’s principle. DFT calculations also explain the different diastereomeric ratio observed for 2-pyridyl and 2-thienyl derivatives in which the isomerization is not possible due to the competitiveness between isomerization barrier and the rate-limiting step (ylide formation barrier). This methodology is applied to the diastereoselective synthesis of a tricyclic thrombin inhibitor.
Keywords:Thermal 1,3-dipolar cycloaddition, Unactivated azomethine ylides, Sequential metal-free
American Chemical Society
info:eu-repo/semantics/article