Premium
Cyclopentadienones via a Tandem C ‐Cyclopropylnitrone Cyclization‐Cycloreversion Sequence
Author(s) -
Erden Ihsan,
Gärtner Christian,
Ma Jingxiang,
Cabrera Gabriel,
Markham Kate,
Azimi Saeed,
Gronert Scott
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700915
Subject(s) - chemistry , tandem , sequence (biology) , stereochemistry , biochemistry , composite material , materials science
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 H ‐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.