Metal-Catalyzed Haloalkynylation Reactions

Metal catalysis has revolutionized synthetic chemistry, leading to entirely new, very efficient transformations, which enable access to complex functionalized molecules. One such new transformation method is the haloalkynylation reaction, in which both a halogen atom and an alkynyl unit are transferred to an unsaturated carbon‐carbon bond. This minireview summarizes the development of metal‐catalyzed haloalkynylation reactions since their beginning about a decade ago. So far, arynes, alkenes and alkynes have been used as unsaturated systems and the reactivities of these systems are summarized in individual chapters of the minireview. Especially, the last few years have witnessed a rapid development due to gold‐catalyzed reactions. Here, we discuss how the choice of the catalytic system influences the regio‐ and stereoselectivity of the addition.

Pd-Catalyzed double carbopalladation/syn-insertion cascade reactions toward medium-size sulfoximine heterocycles

With the assistance of Ac in sulfoximine as a protecting group (PG) and MeOH as a de-PG agent, Pd-catalyzed multicomponent reactions were developed to access indene-fused medium-size sulfoximine heterocycles. The reactions proceeded smoothly under exceptionally mild conditions to produce polyheterocyclic sulfoximines with regiospecificity and good functional group tolerance. A double carbopalladation/syn-insertion of triple bond sequences was proposed tothis transformation.

Synthesis of polycyclic sultams via a palladium-catalyzed reaction of 1-bromo-2-(cyclopropylidenemethyl)benzenes with 2-alkynylbenzenesulfonamides

Polycyclic sultams are efficiently synthesized through a palladium-catalyzed tandem reaction of 1-bromo-2-(cyclopropylidenemethyl)benzenes with 2-alkynylbenzenesulfonamides via double carbometallation.

A palladium-catalyzed tandem reaction of 2-alkynylbenzenesulfonamides with 2-(2-bromoarylidene)cyclobutanones

The core of benzo[f][1,2]thiazonin-5(4H)-one 3,3-dioxide is efficiently assembled through a palladium-catalyzed tandem reaction of 2-alkynylbenzenesulfonamides with 2-(2-bromobenzylidene)cyclobutanones via double carbometallation. A range of polycycles with a nine-membered sultam ring are generated in moderate to good yields.

Generation of 6H-benzo[f]cyclopenta[d][1,2]thiazepine 5,5-dioxides via a palladium-catalyzed reaction of 2-(2-alkynyl)benzenesulfonamide

An efficient approach for the assembly of 6H-benzo[f]cyclopenta[d][1,2]thiazepine 5,5-dioxides via a palladium-catalyzed tandem reaction of 2-(2-alkynyl)benzenesulfonamide with 2-alkynylvinyl bromide is reported. This transformation proceeds smoothly through a double carbopalladation with high efficiency.