Unexpected rate retardation by 4-alkyl substituents in neutral electron demand diels-alder reactions of 2-(3-butenyl)-1,2-dihydropyridines

Abstract

Sustmann's equation gives insight into the slower intramolecular reactivity of 4-alkyl-2-(3-butenyl)-1, 2-dihydropyrldines 2a – 2f relative to the parent 1a . Steric effects are inconsistent with the observed rate data.