Alkyne derivatives coupling conditions, terminal alkynes

Under certain conditions, alkynes can be coupled to aryl halides.280 When aryl halides react with copper acetylides to give 1-aryl alkynes such as 431, the reaction is known as Stephens-Castro coupling.28l Both aliphatic and aromatic substituents can be attached to the alkyne unit, and a variety of aryl iodides has been used. A palladium-catalyzed variation is also known in which an aryl halide reacts with a terminal alkyne to give derivatives such as 434. In this variation, called the Sonogashira coupling,2 2 jhe reaction is catalyzed by... 

In 2006, the group of Artok showed that 5-aryl-2(5H)-furanones could be prepared in moderate to good yields by a rhodium-catalyzed carbonylative arylation of internal alkynes with aryl boronic acids (Scheme 1.9a) [22]. a,P-Unsaturated ketones (chal-cone derivatives) were formed as the major product when some TFA (trifluoroacetic acid) was added under the same reaction conditions [23a]. By varying the catalytic system, indanones could be produced as the main product [23b]. The chemical behavior of terminal alkynes is different, and either a,P-unsaturated ketones or furans starting from propargylic alcohols can be achieved (Scheme 1.9b) [24, 25]. In the case of vinyl ketones, 1,4-diketones were obtained by rhodium-catalyzed coupling of arylboronic acids in the presence of 20-40 bar of CO [26]. In 2007, Chatani demonstrated that indenones could be accessed by a carbonylative rhodium-catalyzed cyclization of alkynes with 2-bromophenylboronic adds (Scheme 1.9c) [27]. Here, the key intermediate is a vinylrhodium(I) spedes that is formed by transmetaUation of RhCl with 2-bromophenylboronic acid followed by insertion of... 

Two possible approaches were shown for the Sonogashira cross-coupling/ benzannulation of enyne with diyne cascade transformation (Scheme 14.19) [11a]. Accordingly, three-component coupling between dihalide 41 and two molecules of terminal diyne produced phenanthren-9(10//)-one derivatives 43 with modest yields under Sonogashira cross-coupling conditions (path A). Incorporation of two different substituents to the final product 46 was achieved via a stepwise addition of terminal alkynes (path B). 

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