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.
Aldonitrones derived from n class="Chemical">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.
Authors: Max R Friedfeld; Michael Shevlin; Grant W Margulieux; Louis-Charles Campeau; Paul J Chirik Journal: J Am Chem Soc Date: 2016-03-01 Impact factor: 15.419
Authors: Edward Richmond; Kenneth B Ling; Nicolas Duguet; Lois B Manton; Nihan Çelebi-Ölçüm; Yu-Hong Lam; Sezen Alsancak; Alexandra M Z Slawin; K N Houk; Andrew D Smith Journal: Org Biomol Chem Date: 2015-02-14 Impact factor: 3.876