Open AccessCatalytic Cycloisomerization onto a Carbonyl Oxygen
Author(s) -
Shicheng Shi,
Jonathan L. Kuo,
Tao Chen,
Jack R. Norton
Publication year - 2020
Publication title -
organic letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.94
H-Index - 239
eISSN - 1523-7060
pISSN - 1523-7052
DOI - 10.1021/acs.orglett.0c02272
Subject(s) - cycloisomerization , chemistry , isomerization , catalysis , radical , ring (chemistry) , oxygen , medicinal chemistry , photochemistry , oxygen atom , organic chemistry , molecule
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.