Spirocyclization enhances the Diels-Alder reactivities of geminally substituted cyclopentadienes and 4H-pyrazoles

Title Spirocyclization enhances the Diels-Alder reactivities of geminally substituted cyclopentadienes and 4H-pyrazoles
Authors Brian J Levandowski; Nile S Abularrage; Ronald T Raines
Journal Journal of physical organic chemistry
DOI 10.1002/poc.4478
Abstract The Diels-Alder reactivity of 5-membered dienes is tunable through spirocyclization at the saturated center. As the size of the spirocycle decreases, the Diels-Alder reactivity increases with the cyclobutane spirocycle, spiro[3.4]octa-5,7-diene, being the most reactive. Density functional theory calculations suggest that spiro[3.4]octa-5,7-diene dimerizes 220,000-fold faster than 5,5-dimethylcyclopentadiene and undergoes a Diels-Alder reaction with ethylene 1,200-fold faster than 5,5-dimethylcyclopentadiene. These findings show that spirocyclization is an effective way to enhance the Diels-Alder reactivity of geminally substituted 5-membered dienes.
Citation Brian J Levandowski; Nile S Abularrage; Ronald T Raines.Spirocyclization enhances the Diels-Alder reactivities of geminally substituted cyclopentadienes and 4H-pyrazoles.
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