Visible Light-Induced[3+2]Annulation Reaction of Alkenes with Vinyl Azides:Direct Synthesis of Functionalized Pyrroles

A photocatalytic[3+2]annulation of alkenes with vinyl azides was developed under irradiation by visible light in the presence of organic dye photocatalysts.Broad substrate scope and high functional group tolerance were demonstrated by more than 50 examples.The reaction provides a novel and efficient method for the synthesis of polyfunctionalized pyrroles under very mild metal-free conditions without other additives.

Synthesis of Unprotectedα-Tertiary Amines and 1,2-Amino Alcohols from Vinyl Azides by Light Induced Denitrogenative Alkylarylation/Dialkylation

Sterically congestedα-tertiary primary amines are ubiquitous substructures in pharmaceutical and agrochemical agents yet are challenging to access.Herein,straightforward photoredox-catalyzed access to structurally diverseα,α,α-trisubstituted primary amines from denitrogenative alkylarylation or dialkylation of vinyl azides with N-hydroxyphthalimide(NHPI)esters and cyanoarenes or aryl aldehydes has been developed.The use of vinyl azide as a precursor to a primary aminewas enabled by the dual role of the Hantzsch ester to form an electron donor-acceptor complex and serve as a sacrificial reductant.This strategy provides a modular synthesis ofα-tertiary primary amines,including unprotected 1,2-amino alcohols,from simple materials with excellent functional group tolerance.The synthetic applicability of this method was demonstrated by streamlined access to 2,2-disubstituted tetrahydroquinolines.Preliminary investigations support two parallel reductive photocatalytic cycles allowing for the denitrogenative alkylarylation or dialkylation of vinyl azides via decarboxylative radical addition followed by heteroradical cross-coupling betweenα-amino radicals and aryl anion radicals or ketyl anion radicals.

Asymmetric catalytic alkylation of vinyl azides with 3-bromo oxindoles: water-assisted chemo-and enantiocontrol

A highly chemo-and enantioselective alkylation of vinyl azides with 3-bromo-3-substituted oxindoles was achieved through a chiral N,N′-dioxide/Ni(OTf)2-mediated conjugate addition/water addition/elimination tandem process. Water was critical to the chemo-and enantioselectivity. The hydrated Na3PO4 acted as both a base and a reservoir to regulate the amount of water in solution. A wide range of enantioenriched oxindoles having α-carbonyl-substituted all-carbon quaternary stereocenters were achieved in good yields and good ee values(51 examples, up to 90% yield, 97% ee). Easy transformations of products to analogues of(+)-physovenine and(+)-desoxyeseroline enhanced the synthetic value. Mechanistic studies including control experiments, kinetic studies, and density functional theory(DFT) calculations, enabled a proposition of a possible catalytic cycle along with transition states to elucidate the reaction process and chiral induction.

Synthesis of Phenanthridine and Quinoxaline Derivatives via Copper-Catalyzed Radical Cyanoalkylation of Cyclobutanone Oxime Esters and Vinyl Azides

Main observation and conclusion A copper-catalyzed radical cyclization of cyclobutanone oxime esters and vinyl azide is described.This method provides facile access to cyanoalkyl-substituted phenanthridines and quinoxalines with excellent isolated yields.Moreover,these reactions proceed under mild conditions with a board substrate scope and excellent functional group tolerance.