Synthesis of Heteroaryl Thiazolidinones and Azetidinones under Conventional and Ultrasonication Methods

Abstract

A simple and an efficient protocol for the synthesis of differently substituted thiazolidinones was reported under conventional and also under ultrasonication in one‐step and in two‐step methodologies. Heteroaryl Schiff's bases were also exploited to develop heteroaryl azetidinones under both conventional and ultrasound irradiation.

Torquoselective Mechanochemical Activation of the Staudinger Reaction To Form β-Lactams

“…Upon initial contact of the reactants at the transition state TS1 , the substituents at C3 and C4 positions slightly favor the exo approach for both ketenes (thus placing both substituents far from the imine). However, in agreement with the torquoelectronic effect, − the distinct electronic properties of the two ketene substituents affect the second and rate-limiting step via TS2 . Thus, the chloro-ketene reaction prefers the exo route by 12 kcal/mol, whereas the CHO-ketene reaction favors the endo one by 0.5 kcal/mol.…”

“…Despite a plethora of synthetic proposals to enhance reactivity while keeping selectivity, including photochemical and microwave promotion, mechanochemical activation , has not yet been considered in the synthesis of β-lactams to our best knowledge. Yet, some experimental work reported that ultrasonication methods provided shorter reaction times as well as higher β-lactam yields . Moreover, it has been demonstrated that the β-lactam ring is indeed a mechanophore capable of undergoing a mechanically activated cycloelimination reaction .…”