Exo-trig selenocyclization of secondary allylic carboxamides using Woollins' reagent: en route to 2,5-disubstituted selenazolines

We report microwave-assisted selenation and exo-trig cyclization of secondary allylic carboxamides using Woollins' reagent, a serendipitous finding observed during an attempt to synthesize N-allylbenzoselenoamide compounds. This resulted in the first reported synthesis of 2-aryl-5-methyl selenazolines. Twenty-one diversified selenazolines and three late-stage-functionalized drug molecules were synthesized in 42-93% and 25-52% yield, respectively, and these were evaluated further for their anti-proliferative activity.

Recent advances in organophosphorus-chalcogen and organophosphorus-pincer based macrocyclic compounds and their metal complexes

The design and development of phosphorus based macrocycles containing one or more other heteroatoms is of crucial importance for the enhancement of modern synthetic chemistry. In recent years focus on phosphorus based macromolecules has led to intriguing and innovative structures with a variety of applications, including photophysical and host-guest properties, and in organic synthesis. This article summarizes the recent advancements in the synthesis of macrocycles that consist of organophosphorus-chalcogen (P-E, P[double bond, length as m-dash]E; E = O, S, Se) and organophosphorus-pincer based macrocyclic ligands and their transition metal complexes with emphasis given to synthetic methodologies. The reactions involve the modification of simple macrocycles with phosphorus sources or phosphorus-based chalcogenating reagents. Transition metal complexes of phosphine-based macrocyclic pincer ligands and their reactivity are also included.

Novel Five- and Six-Membered Rings of Phosphorus-Selenium Heterocycles from Selenation of Amido-Schiff Bases

Woollins' reagent, [2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide], serving as a selenating-reductive cycloaddition reagent, reacts with nonconjugated amido-Schiff bases to give the corresponding six-membered 1,3,4-selenadiazoles via a ring-expansion accompanied by an additional selenation/cyclization to the imine bond and C=O group; meanwhile, under the same reaction conditions, the selenation of conjugated amido-Schiff bases leads to a series of fused heterocycles with two five-membered rings. Eight single-crystal X-ray structures confirming the formation of these five- and six-membered heterocycles are discussed.