Work

Catalytic Cycloisomerization onto a Carbonyl Oxygen

Year: 2020

Type: article

Abstract: We have found that terminal N -vinylindoles bearing cycloalkanone substituents are excellent hydrogen atom acceptors, generating α-aminyl radicals with a variety of catalysts (Co(II)/H 2 or Co(III)Cl precatalysts with silane reductants). These radicals can be converted to internal vinylindoles but eventually add to the oxygen of the cycloalkanone substituents. These cyclizations eventually furnish a densely functionalized dihydrofuran (a net cycloisomerization). The internal vinylindoles are slowly converted to the dihydrofurans, but the final cycloisomerization/isomerization ratio is affected by the size of the cycloalkanone ring (seven- and eight-membered rings give the highest ratio). These results demonstrate how HAT can isomerize substrates in nonintuitive ways, here leading to the first HAT-promoted formation of a C–O bond.

Source: Organic Letters

DOI: 10.1021/acs.orglett.0c02272

Authors: Shicheng Shi, Jonathan L. Kuo, Tao Chen, Jack R. Norton

Institution: Columbia University

Language: English

Topic: Radical Photochemical Reactions

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funders: National Institute of General Medical Sciences, Division of Graduate Education

Awards: Catalysis of Tin-Free Radical Reactions Under H2, The Rates of Reaction Relevant to Aerobic Oxidation Catalysis by Palladium, G3171619026, G822764649