Palladium-Catalyzed Cascade 5-endo-dig Cyclization of Ynamides to Form 4-Alkynyloxazolones

Abstract

The selective synthesis of 4-alkynyloxazolones and their further applications as substrates to electrophile-promoted nucleophilic cyclization have been developed. The reaction of ynamides with terminal alkynes proceeded smoothly to give 4alkynyloxazolones in the presence of a catalytic amount of palladium(II) acetate. The products were obtained with the sequential formation of new C−C and C−O bonds via a cascade procedure. The first step involved a carbon−oxygen bond formation, via a 5endo-dig closure, which was confirmed by X-ray analyses of the crystalline sample. Subsequently, the reaction of 4-alkynyloxazolones with an electrophilic selenium source gave 3-phenylselanyl benzofuran derivatives via an electrophile-promoted nucleophilic cyclization.

A base-free copper-assisted synthesis of C2-symmetric spirotelluranes and biaryls based on divergent stoichiometry of Na2Te

“…In the past few decades, organochalcogen (S, Se, and Te) chemistry has received significant attention amongst chemists due to its use in the field of synthetic organic chemistry, 1–3 dyes, 4 and biology. 5 Organotelluriums have been studied for years and show promising activities for the decomposition of peroxides, 6 as radical chain braking antioxidants, 7 and as antitumor 8 and antileishmanial 9 agents (Chart 1).…”

Organohypervalent heterocycles

“…The last few decades has witnessed tremendous growth in the interest in organochalcogen (S, Se, and Te) chemistry by chemists due to their immense utilization in the field of synthetic organic chemistry, [179][180][181][182][183][184][185][186][187][188] dyes, 189 and biological applications. [190][191][192][193][194][195] Certain hypervalent heterocycles of these elements have been synthesized and well-characterized.…”