Direct alkynylation

A wide variety of organoalkynyl derivatives of cotarnine hydrochloride, a cyclic iminium salt with rich biological activity, were prepared from the direct alkynylation of cotarnine hydrochloride using silver(l) alkynyls.180 Substituted enynes were prepared from the coupling reactions of silver alkynyls with the palladium allyl intermediates, which was... 

Alkynylzinc reagents. The direct alkynylation of aldehydes is subject to asymmetric induction in the presence of a chiral base such as (-l-)-Af-methylephedrine. Addition to the C=N bond of A-tosylimines and nitrones by this procedure is also successful. ... 

The Favorsky reaction, the interaction between terminal acetylenes and carbonyl compounds in the presence of powdered dry KOH, is of limited importance for the pyrazole series, although the hydroxyacetylenic group is one of the most important protecting groups. However, most often, such an alcoholacetylenic substituent is introduced by direct alkynylation of the corresponding iodopyrazoles with... 

In 2010, we reported the direct alkynylation of 2-quinoxalinone and p-tolylacetylene under various base-promoted (Et3N or NaOt-Bu) and... 

The possible mechanism of the direct alkynylation of 2-quinoxalinone with p-tolylacetylene via Pd/Cu-catalyzed phosphonium coupling is proposed. It may involve the following seven-step cascade with two separate Pd/Cu catalytic cycles via C—H/C—OH bond activations (1) tautomer-ization of 2-quinoxalinone to 2-quinoxalinol in the presence ofEt3N (2) activation of 2-quinoxalinol with PyBroP generating the heterocycle— phosphonium intermediate (C-OH bond activation) (3) oxidative... 

In 2010, Shi and coworkers reported direct alkynylation of tautomerizable heterocycles with alkynes using PyBroP in the presence of PdCl2(PPh3)2/ Cul at rt (Condition A) or PdCl2(MeCN)2/cyclohexyl JohnPhos (Condition B) catalysts. Condition A is suitable for substrates with sensitive functional groups and Condition B is applicable to a wider range of substrates (10OL2286). 

Waser and et al. developed a C2-selective direct alkynylation of indoles (174, 66% yield).The reaction, which runs under air at room temperature, relies on a palladium catalyst and hypervalent iodine reagent, triisopro-pylsilylethynyl-l,2-benziodoxol-3(lFJ)-one. The indole ring may be... 

While many advances have been made for direct arylation and alkenylations, the same amount of success has not been achieved for both alkylations and direct alkynylations. 

A metal/organocatalytic direct alkynylation of aldehydes employs copper(I) t-butoxide in t-butanol, together with a prolinol bearing a pendant triphenylphosphine. ° Yields and ee of up to 98/94% are rationalized in terms of copper chelation of organocatalyst (at N, O and P) and alkyne, further organized by 0-H---0 and sp -C-H- -O hydrogen bonds, the latter being unusual in alcoholic solvent, but they are supported by QM calculations. 

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). ... 

For direct alkynylation with TIPS-acetylene, a hypervalent iodine TIPS-acetylene reagent can also be used as demonstrated in Waser s recent works. Alkynylation on C-3 of indole was catalyzed by AuCl (eq 26) and the Wacker cyclization s intermediate was intercepted by the hypervalent iodine TIPS-acetylene (eq 27).2 ... 

Need to alkynylate a thiol Direct alkynylation has been reported using alkynyliodonium salts [103]... 

Using a gold catalyst, the direct alkynylation of pyrroles, indoles, and thiophenes may be achieved using ethynyl benziodoxolones, (135). Extensive mechanistic studies were not conclusive but favour a r-activation process, or an oxidative mechanism. " ... 

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