Activation of acetylene

S. F. Vasilevsky and E. V. Tetryakov (Novosibirsk, Russia), together with J. Elguero (Madrid, Spain), have summarized the synthesis, chemical and spectroscopic properties, and biological activity of acetylenic derivatives of pyrazoles, a field which has shown explosive growth in the past few years. 

Table V summarizes the reduction activity of acetylene with the Co(II)-complex catalysts of various sulfhydryl-containing peptides. Of interest is the high activity of the sulfhydryl- and imidazole-containing peptides such as N-mercaptoacetyl-L-histidine and N-mercaptoacetyl-DL-histidyl-DL-histidine. In addition, the effect of amino-acid residues on the reduction of acetylene with these Co(II) complexes decreases in the order histidine > glycine > cysteine > tryptophan.

In conclusion, subtle variations in the molybdothiol-complex catalysts—ligand substitution, coordination donor atom, and central metal ion—have large effects on the catalytic activity of acetylene reduction. The results presented here may offer useful information for a design of catalysts with optimal activity in such complex systems. 

Sulfoxide, sulfinate and sulfonate are used as activators of acetylenic or vinyl units. Several a, P unsaturated synthons, namely acetylenic sulfoxide (1), vinyl sulfoxide (2), acetylenic sulfinate (3), acetylenic sulfonate (4), and l-propene-l,3-sultone (5) are developed. Their applications in Diels-Alder reactions, heterocycle and alkaloid syntheses are also investigated. For the chiral acetylenic sulfoxide, the sulfoxide moiety not only enables chemical activation of the acetylene unit, it can also induce stereochemical control at the adjacent carbon centers to achieve enantioselective synthesis. 

Propane-l,2- C, specific activity of about 110 mCi mmol" has been synthesized from doubly labelled acetylene in reaction series shown in equation 12. This synthesis included preparation of doubly labelled acetylene from barium carbonate-according to Cox and Warne, nearly quantitative hydrogenation of acetylene to ethylene, addition of hydroiodic acid to the latter to form iodoethane, preparation of ethylmagnesium iodide followed by carbonation to yield propionic acid and reduction o n-propanol with 70-75% yield. The latter yielded a tosylate which was finally reduced to doubly labelled propane 2 with sodium borohydride, and purified by gas chromatography on alumina or silica. Its specific activity was close to the maximal possible specific activity of acetylene (i.e. 124.9 mCi mmol " ). 

Stoeckli, F., and Huguenin, D., Pretreatment and physical activation of acetylene cokes, Fuel, 73(12). 1929-1930... 

Eckenbach, U., Lampman, R.L., Seigler, D.S. et al. (1999) Mosquitocidal activity of acetylenic compounds from Cryptotaenia canadensis. J. Chem. Ecol, 25, 1885-1893. 

A. V. Vasilyev, Electrophilic Activation of Acetylene Compounds in Bronsted Superacids. Reactions of Vinyl Type Cations, Russ. Chem. Rev., 2013, 82,187. 

Hence, it naturally follows that polarization and deformation of acetylene 7t-electron shell depend on atomic number of a cation, which acetylene anion is bonded to. However, activation of acetylene in the reaction with ketoximes via acetylenides assumes the attack of nucleophile to the carbanion-like complex, and this is likely a weak spot of this hypothesis. Nevertheless, the electrophilic assistance of aUcah metal cation (Na+) in the course of nucleophilic addition to acetylene (Scheme 1.13) is confirmed by quantum-chemical calculations (ab initio, STO-3G) [171],... 

As mentioned earlier, in the system KOH/DMSO, there is extra activation of pyrrole anions with a simultaneous increase in their concentration, as well as activation of acetylene (see Section 1.1.1). These effects lead to a significant increase in the reaction rate and allow reducing excessive acetylene pressure. 

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