Alkynyl complexes coupling reactions

Alkyl- and aryl-pyridazines can be prepared by cross-coupling reactions between chloropyridazines and Grignard reagents in the presence of nickel-phosphine complexes as catalysts. Dichloro[l,2-bis(diphenylphosphino)propane]nickel is used for alkylation and dichloro[l,2-bis(diphenylphosphino)ethane]nickel for arylation (78CPB2550). 3-Alkynyl-pyridazines and their A-oxides are prepared from 3-chloropyridazines and their A-oxides and alkynes using a Pd(PPh3)Cl2-Cu complex and triethylamine (78H(9)1397). 

Anionic complexes of boron (boronates, borinates, etc.) have been introduced as convenient reagents in cross-coupling reactions of broad scope, particularly interesting for the transfer of alkynyl and primary alkyl residues, which cannot be accomplished using the standard protocols of the Suzuki-Miyaura reaction. Readily available Ph4BNa can be used as a convenient reagent for phenylation in place of the much more expensive PhB(OH)2, and all four phenyl groups can be utilized when the reaction is carried out with a phosphine-free catalyst in aqueous solutions.244... 

Ir-diphosphine complexes have been shown to catalyze a number of potentially interesting C—C coupling reactions [41]. Special mention should be made of the various transformations of alkynes (cycloaddition, isomerization, dimerization, alkynylation), selected aldol and carbonylation reactions, even though the synthetic potential of some of these reactions has not been explored. 

Generally, the preparation of these species is achieved by (a) coordination of preformed diynes to transition metal centers, and (b) coupling reactions of the alkynyl ligand in mono-alkynyl metal complex precursor. 

B. Coupling Reactions of the Alkynyl Ligand in Mono-Alkynyl Metal Complex Precursors... 

The tantalum(V) calix[4]arene complex 44 provides an interesting scaffold for the construction of an j -PhC2C=CPh ligand upon reaction with an excess of phenylethynyllithium (Scheme 10). The coupling reaction is presumed to proceed via bis-alkynyl 45, which is subsequently attacked at the a-carbon of one of the acetylide ligands to give anion 46, isolated as its lithium salt. The addition of a further equivalent of LiC CPh is probably prohibited by orbital constraints. ... 

The coupling reaction of Fischer carbene complexes, 96, with 3-alkynyl-2-thiophene carboxaldehyde leads to the formation of thieno[2,3-c]pyranones (Scheme 25) <2001TL777, 2002JOC4177>. This reaction is applicable to the oxygenated derivatives. 

Palladium-mediated cydization based on the reactivity of o-alkynyl or alkenyl-phenyl isonitriles have been developed [105]. On the basis of their earlier studies on the three-component synthesis of allyl aryl cyanamides [106], Yamamoto and co-workers reported a palladium-catalyzed three-component coupling reaction of 2-alkynylisocyanobenzenes 122 with allyl methyl carbonate and trimethylsilylazide leading to N-cyanoindoles 125 [107]. One of the key steps of the proposed mechanism is the formation of 7i-allylpalladium carbodiimide 123 and its isomerization to rc-allylpalladium cyanamide complex 124 (Scheme 8.50). 

Alkynyl(phenyl)iodonium salts can be effectively used in palladium(O) or copper(I) catalyzed coupling or carbonylative coupling reactions with various organozirconium complexes (Scheme 57) [117-119]. 

It has been demonstrated by 1H, 13C, and 109Ag NMR that a 7r-alkyne-Ag complex and then an alkynyl silver are formed in situ from alkyne and silver salt under conditions related to those used for Ag-catalysed alkynylation or for Ag/Pd-catalysed sp-sp2 cross-coupling reactions.142 These observations have prompted a rationale of the mechanisms of these reactions. 

Alkynyl(methoxy)borates prepared in situ from an alkynyllithium or sodium and 9-methoxy-9-BBN coupled with 1-alkenyl and aryl halides (Equation (210)).899-902 Addition of triisopropylborate to lithium acetylide yielded an air stable and isolable ate complex that couples with aryl and alkenyl halides (Equation (211)).903 904 Air and moisture stable alkynyltrifluoroborates were probably the most convenient reagents that allow handling in air and coupling reactions in basic aqueous media (Equation (212)).46... 

---