Sonogashira coupling product

Concerning other metals, Sonogashira coupling products have also been observed in the reaction of Ag(l)-carbenes [133] and Au(I)-supported carbenes [134] in low to moderate yields, but only under harsh conditions (more than 100°C). In this regard, NHC based catalysts for Sonogashira reactions have been supported on different materials that include clays [135], polymers [136] and peptides [137]. 

Direct Alkynylation. Ni-catalyzed direct alkynylation on azoles has been achieved without assistance of halogen-mediated activation by using oxygen as oxidant in the catalytic cycle. TIPS-acetylene was added to a variety of nonhalogenated azoles to produce the Sonogashira coupling products (eq 25). ... 

The reaction was monitored by HPLC to clarify the reaction rate and mechanism. The reaction undergoes a transformation from the aryl iodide to the Sonogashira coupling product as an... 

The treatment of 3-iodo-4-methoxycoumarin 11 with phenylacetylene under Sonogashira C-C coupling conditions resulted also in the high-yield formation of the furo[3,2-c]coumarin 13 (Scheme 4) [61], In this reaction, the tri-ethylamine used as base induced the N2-type demethylation of the Sonogashira coupling product 12, thus enabling a subsequent copper-assisted cyclization. 

A microwave-driven Sonogashira coupling step is involved in the total synthesis of azaphilones, a structurally diverse family of natural products containing a highly oxygenated bicyclic core and a quaternary center. Porco and his colleagues have described the alkynylation of densely functionalized bromobenzaldehydes with... 

Substituted propargylic carbonates react with terminal acetylenes in the presence of a catalytic amount of Pd(PPh3)4 and Cul to produce Sonogashira-type cross-coupling products (Eq. 9.114) [84]. Presumably, the reaction proceeds through an allenylpalladium complex. Addition of a salt, such as KBr, increased the yield of the coupling product. Only tetrasubstituted allenes could be obtained by this procedure. 

Like halopyridines, diazines participate in Sonogashira coupling too. 3,6-dimethyl-2-chloropyrazin, for example on coupling with phenylacetylene under standard conditions, gave the desired compound in good yield, which was further reduced to give a natural product (7.36.)51 (NB. the Heck reaction, which could be considered as an alternate approach would be expected to furnish predominantly the c/.v-olcfin as product). 

The mildness of the Sonogashira coupling conditions allows for the functionalization of otherwise sensitive substrates too. The dibromo derivative of 2,1,3-benzothiadiazole was reacted with different pyridylacetylenes to give the expected fluorescent products (8.28.). The intermediate mono-coupled product was also isolated in each case, although in varying yield.37... 

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