Oxidative oxy-cyclization of 2-alkynylbenzamide enabled by TBAB/Oxone: switchable synthesis of isocoumarin-1-imines and isobenzofuran-1-imine

A TBAB-controlled switchable synthesis of isocoumarin-1-imine and isobenzofuran-1-imine from 2-alkynylbenzamide in water is described in this paper.

Palladium-Catalyzed Cyclization of N-Acyl- o-alkynylanilines with Isocyanides Involving a 1,3-Acyl Migration: Rapid Access to Functionalized 2-Aminoquinolines

A simple and expedient approach for the synthesis of functionalized 2-aminoquinolines via palladium-catalyzed annulation of N-acyl- o-alkynylanilines with isocyanides has been developed with high atom economy, in which an unconventional 6- endo-dig cyclization process is observed. Further investigations of the mechanism demonstrated that an intramolecular acyl migration of the N-protecting groups was involved in this transformation.

Dihalohydration of Alkynols: A Versatile Approach to Diverse Halogenated Molecules

In this paper we outline how dihalohydration reactions of propargylic alcohols can be used to access a wide variety of useful halogenated building blocks. A novel procedure for dibromohydration of alkynes has been developed, and a selection of dichloro and dibromo diols and cyclic ethers were synthesized. The dihalohydration of homo-propargylic alcohols provides a useful route to 3-halofurans, which were shown to readily undergo cycloaddition reactions under mild conditions. Finally, a novel ring expansion of propargylic alcohols containing a cyclopropylalkyne provides access to halogenated alkenylcyclobutanes.

Regioselective 5-exo-dig oxy-cyclization of 2-alkynylbenzamide for the synthesis of isobenzofuran-1-imines and isobenzofuran

A TBAB-mediated regioselective radical cyclization of 2-alkynylbenzamide is described herein for the synthesis of isobenzofuran-1-imines. The reactions proceeded smoothly under mild conditions.

Highly regioselective, electrophile induced cyclizations of 2-(prop-1-ynyl)benzamides

We report an electrophile promoted, highly regioselective (∼100%) synthesis of 5-membered haloimidiates from 2-(1-alkynyl)benzamides under metal free conditions.

Gold(I)-Catalyzed Cyclization/Carbonylation Cascade Reaction of 1,6-Diynes: An Access to β,γ-Unsaturated Ketones

A gold-catalyzed cyclization/carbonylation cascade reaction of 1,6-diynes is reported. The reaction goes through 6-exo-dig and 6-endo-dig cyclizations in sequence, followed by hydration to provide the β,γ-unsaturated ketones with moderate to high yields under mild reaction conditions. This is the first example of intercepting the postulated 1,3-oxazine vinylgold intermediate with another pendant alkyne, which not only verifies the proposed mechanism but also provides the ketone products with cyclized 1,2,3,6-tetrahydropyridine or 3,6-dihydro-2H-pyran frameworks from corresponding diynes.