The [4+2] cycloaddition of donor–acceptor cyclobutanes and nitrosoarenes
作者:Naresh Vemula、Andrew C. Stevens、Tyler B. Schon、Brian L. Pagenkopf
DOI:10.1039/c3cc47775d
日期:——
The Yb(OTf)3 catalyzed [4+2] cycloaddition between donor-acceptorcyclobutanes and nitrosoarenes is disclosed. This method facilitates the synthesis of tetrahydro-1,2-oxazines in good to excellent yields as single diastereomers. Except for a few electron-deficient nitrosoarenes, excellent regioselectivity was observed throughout these studies.
Ytterbium Triflate Catalyzed Synthesis of Alkoxy-Substituted Donor−Acceptor Cyclobutanes and Their Formal [4 + 2] Cycloaddition with Imines: Stereoselective Synthesis of Piperidines
作者:Mahmoud M. Abd Rabo Moustafa、Brian L. Pagenkopf
DOI:10.1021/ol102062t
日期:2010.11.5
A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor−acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)3. Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity.
Synthesis of Tetrahydro-1,2-oxazines and Pyrrolidines via Cycloadditions of Donor-Acceptor Cyclobutanes and Nitrosoarenes
作者:Naresh Vemula、Brian L. Pagenkopf
DOI:10.1002/ejoc.201500542
日期:2015.8
During efforts to expand the scope of Lewis-acid-catalyzed [4+2] cycloaddition between donor–acceptorcyclobutanes and nitrosoarenes, an unexpected formation of pyrrolidine products was discovered when 50 mol-% of MgI2 was used as a Lewis acid. It was also observed that the electronics of the nitrosoarene and judicious selection of the Lewis acid catalyst have a profound effect on the regioselectivity