Alkynes nonfunctionalized

Apparently, the simplest approach would be the carbometalation reaction or, more specifically, the vinylmetalation of alkynes [1-8]. The addition of organo-metallic reagents to functionalized or nonfunctionalized, terminal or nonterminal alkynes, in which the resulting organometallic compound can react with electrophiles, is defined as the carbometalation reaction (Scheme 1). It has been widely explored and applied in the regio- and stereoselective preparation of numerous vinyl metal species. 

The insertion of CO in the Pd-C bond to form an acylpalladium species can be supported by Co2(CO)g as co-catalyst [9]. This finding helped improve the chemoselectivity of the Pd-catalyzed hydroformylation of alkynes [10]. Under the conditions shown in Scheme 1.42, almost no hydrogenation products, such as saturated aldehydes or nonfunctionalized olefins, were formed. 

Cycloaromatization of enediynes by diradical pathways in the thermal-and metal-catalyzed routes allows nonfunctionalized benzene derivatives to be prepared. The aromatization of enediynes by the action of nucleophiles produces aromatic compounds retaining the respective nucleophilic residue [333, 334]. The ruthenium-catalyzed reaction gives rise to the synthesis of various functionalized benzene derivatives. Thus, adding water, alcohols, aniline, acetylacetone, pyrroles, and dimethyl malonate to acyclic and aromatic enediynes 3.711 at 100°C for 12-24 hours in the presence of TpRuPPh3(MeCN)2PF6 (10 mol%) led to the functionalized benzenes 3.712 in satisfactory yields (Scheme 3.79) [334]. This cyclization involves regioselective nucleophilic attack of enediyne 3.711 to form a, TT-vinylruthenium intermediate 3.714 which finally converts to the benzene derivative. Experiment with labeled hydrogen atoms showed that the ruthenium n-alkyne complexes 3.713 are catalytically active. 

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