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Cyclopentadienones via a tandem C-cyclopropylnitrone cyclization-cycloreversion sequence.

ABSTRACT: Aldonitrones derived from spiro[2.4]hepta-4,6-diene-1-carbaldehyde and its benzo analog undergo a tandem uncatalyzed intramolecular cyclopropane-nitrone cyclization-5,6-dihydro-1,2-oxazine cycloreversion to give cyclopentadienones. Similarly, the NH-nitrone generated in situ from spiro[cyclopropane-1,1'-indene]carbaldehyde oxime leads to benzocyclopentadienone (1H-inden-1-one) by the same mechanism. DFT calculations are in favor of a concerted yet highly asynchronous pathway for the cyclizations. Control experiments with the dihydro and tetrahydro derivatives show that the spirocyclopentadiene unit is essential for the success of the reaction, invoking spiroconjugative effects for increased cyclopropane reactivity.

SUBMITTER: Erden I

PROVIDER: S-EPMC5708562 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Cyclopentadienones via a tandem <i>C</i>-cyclopropylnitrone cyclization-cycloreversion sequence.

Erden Ihsan I Gärtner Christian C Ma Jingxiang J Cabrera Gabriel G Markham Kate K Azimi Saeed S Gronert Scott S

European journal of organic chemistry 20170914 34

Aldonitrones derived from spiro[2.4]hepta-4,6-diene-1-carbaldehyde and its benzo analog undergo a tandem uncatalyzed intramolecular cyclopropane-nitrone cyclization-5,6-dihydro-1,2-oxazine cycloreversion to give cyclopentadienones. Similarly, the NH-nitrone generated in situ from spiro[cyclopropane-1,1'-indene]carbaldehyde oxime leads to benzocyclopentadienone (1<i>H</i>-inden-1-one) by the same mechanism. DFT calculations are in favor of a concerted yet highly asynchronous pathway for the cycli ...[more]

PMID: 29200938

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