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Catalytic Cycloisomerization onto a Carbonyl Oxygen.

ABSTRACT: We have found that terminal N-vinylindoles bearing cycloalkanone substituents are excellent hydrogen atom acceptors, generating ?-aminyl radicals with a variety of catalysts (Co(II)/H2 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.

SUBMITTER: Shi S

PROVIDER: S-EPMC7456208 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Catalytic Cycloisomerization onto a Carbonyl Oxygen.

Shi Shicheng S Kuo Jonathan L JL Chen Tao T Norton Jack R JR

Organic letters 20200722 15

We have found that terminal <i>N</i>-vinylindoles bearing cycloalkanone substituents are excellent hydrogen atom acceptors, generating α-aminyl radicals with a variety of catalysts (Co(II)/H<sub>2</sub> 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 viny ...[more]

PMID: 32697584

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