Metal‐Catalyzed Haloalkynylation Reactions

Abstract

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 metalcatalyzed 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.

Palladium-catalyzed multi-component Heck alkynylcarbonylation of unactivated alkenes for synthesis of β,γ-alkynoates

“…Haloalkynes are appealing starting materials in organic synthesis because they are highly reactive, easy to prepare and readily available from inexpensive terminal alkynes. 10,11 While pursuing new catalytic approaches towards the functionalisation of haloalkynes, we developed a series of transition-metal-catalysed haloalkynylation reactions. 12 To our knowledge, the regioselective synthesis of β,γ-alkynoates via a Pd-catalysed multi-component alkynylcarbonylation reaction using haloalkynes as electrophilic reagents is yet to be reported.…”

The Alkynylative Difunctionalization of Alkenes

“…Similarly, the alkynylative difunctionalization of alkenes has been well developed. Although there are several reviews, [18–22] these reviews are too limited to a certain aspect and are targeted summaries. Particularly, considerable progress has been made in catalytic asymmetric studies recently, however, there is no relevant review to summarize to date.…”

Gold(I)-Catalyzed Selective Hydroarylation of Indoles with Haloalkynes

“…Haloalkynes are important intermediates and versatile building blocks for synthetic organic chemistry due to their versatile reactivity in a number of chemical transformations . Traditionally, haloalkynes are regarded as a source of acetylides via metal–halogen exchange.…”

“…Literature reports indicate that a cation vinyl gold intermediate will be directly formed after the coordination of the gold catalyst to the triple bond on the haloalkyne, − which would undergo a trans -nucleophilic attack of the indole to provide vinyl indole. To investigate this, an X-ray diffraction analysis of suitable crystals of 3 confirmed the assigned regio- and stereoselectivity (CCDC 2167592, Scheme ) and provided useful structural data for further modeling studies.…”