Recent advances in the transition metal-free synthesis of heterocycles from α,β-unsaturated ketones

Abstract

Heterocyclic compounds are an inevitable part of our life. These important classes of molecules have a wide range of applications starting from life-sustaining drugs to agrochemicals. Numerous methods, including metal and non-metal mediated protocols, are documented to synthesise complex and straightforward heterocyclic entities. The metal-free protocols have more significance over the metal-catalyzed ones when the toxicity associated with the metal catalyst is considered. On the other hand, α,β-unsaturated ketones are essential building blocks in synthetic organic chemistry. The presence of multiple reaction sites makes conjugated carbonyls suitable substrates for constructing a vast array of heterocycles and carbocycles. Herein, the review's primary focus is to highlight the transition metal-free methodologies developed for synthesising various heterocyclic compounds by utilising α,β-unsaturated ketones as valuable synthons during the period of 2009 to 2020.