Studies On Direct Vinylation Of ?,?-Sec-Amides With Potassium Organotrifluoroborate And The Cascade Of An Imino Nazarov Reaction:One-pot Access To Polysubstituted Cyclopent-2-enimines

Polysubstituted cyclopentylamines scaffolds are ubiquitous in both natural products and biologically important molecules.The classical Nazarov reaction through a conrotatory 4?-electron electrocyclic ring closure of a pentadienyl cation is one of the most important protocol to construct these skeletons.However,the study of Imino-Nazarov cyclization,which features electrocyclic ring closure of pentan-1,4-diene-3-imines,remain scarce till now.On the basis of our long-standing interest in amide activation,in this paper,a one-pot cascade of direct vinylation of ?,?-unsaturated secondary amides with potassium organotrifluoroborates and the subsequent Imino-Nazarov cyclization to prepare polysubstituted cyclopentenimines has been reported,the main results and observations are listed as follows:(1)A high-yielding synthesis of polysubstituted pentan-1,4-diene-3-imines from?,?-unsaturated secondary amides and potassium organotrifluoroborates has been developed.(2)On the basis of direct vinylation of ?,?-unsaturated secondary amides with potassium organotrifluoroborates cascaded with imino-Nazarov cyclization,a one-pot preparation of polysubstituted cyclopentenimines has been developed.(3)The preliminary study of reaction mechanism has been performed.