Alkyne complexes synthesis

Octadicarbonyldicobalt alkyne displacement, 71 cobalt-alkyne complex synthesis, 70-71... 

Martin C, Sierra M, Alvarez E, Belderrain TR, Perez PJ. Hydrotris(3-mesitylpyrazolyl) borato copper(I) alkyne complexes synthesis, structural characterization and rationalization of their activities as alkyne cyclopropenation catalysts. Dalton Trans. 2012 41 5319-5325. 

Initial step is the formation of a dicobalthexacarbonyl-alkyne complex 5 by reaction of alkyne 1 with dicobaltoctacarbonyl 4 with concomitant loss of two molecules of CO. Complex 5 has been shown to be an intermediate by independent synthesis. It is likely that complex 5 coordinates to the alkene 2. Insertion of carbon monoxide then leads to formation of a cyclopentenone complex 6, which decomposes into dicobalthexacarbonyl and cyclopentenone 3 ... 

Went, Michael J., Synthesis and Reactions of Polynuclear Cobalt-Alkyne Complexes. 41 69... 

Similar to Cp2TiCl2, T OPr1) as a less expensive precursor, can also be utilized for the synthesis of titanium-alkyne complexes.13 The reactivity of the (Pr10)2Ti-alkyne complexes toward a variety of substrates has been investigated.14 In the case of unsymmetrical alkynes as a starting material, the less hindered carbon of the resultant... 

Scheme 5 Synthesis of manganese allenylidenes 5 from 7i-alkyne complex 4...

Transition-metal-promoted cycloaddition is of much interest as a powerful tool for synthesis of carbocyclic stmcture in a single step. Utilization of carbon monoxide as a component of the cycloaddition reaction is now widely known as the Pauson-Khand reaction, which results in cyclopentenone formation starting from an alkyne, an alkene, and carbon monoxide mediated by cobalt catalyst. Although mechanistic understanding is limited, a commonly accepted mechanism is shown in Scheme 4.16. Formation of dicobalt-alkyne complex followed by alkene... 

Schore NE (1991) Org React 40 1 Schore NE (1991) The Pauson-Khand reaction. In Trost BM (ed) Comprehensive organic synthesis, vol 5. Pergamon Press, Oxford, p 1037 Pauson PL (1985) Tetrahedron 41 5855 Schore NE (1995) Transition metal alkyne complexes Pauson-Khand reaction. In Abel EW, Stone EGA, Wilkinson G (eds) Comprehensive organometallic chemistry II, vol 12. Pergamon Press, Oxford, p 703 Iwasawa N (1992) Chem Lett 473... 

In both of the Ni-mediated steps in this synthesis, the Ni-alkyne complex is acting as an acyl anion, in one case opening an epoxide and in the other case adding to the aldehyde in an intramolecular sense. Such Ni-reduced phenylalkynes are among the easiest to prepare and least expensive of acyl anion equivalents. 

The reaction of alkenes (and alkynes) with synthesis gas (CO + H2) to produce aldehydes, catalyzed by a number of transition metal complexes, is most often referred to as a hydroformylation reaction or the oxo process. The discovery was made using a cobalt catalyst, and although rhodium-based catalysts have received increased attention because of their increased selectivity under mild reaction conditions, cobalt is still the most used catalyst on an industrial basis. The most industrially important hydrocarbonylation reaction is the synthesis of n-butanal from propene (equation 3). Some of the butanal is hydrogenated to butanol, but most is converted to 2-ethylhexanol via aldol and hydrogenation sequences. 

Synthesis and Reactions of Polynuclear Cobalt-Alkyne Complexes... 

In 1974, Dickson and Fraser reviewed the already substantial area of cobalt-alkyne complexes.1 Since then the number of examples and applications of this class of organometallic compounds, especially dinuclear complexes, has increased enormously. This review will present the chemistry of polynuclear cobalt-alkyne complexes, with emphasis on the more recent developments. Although there have been many exciting fundamental discoveries, this is a maturing area of research that is finding many important applications in organic synthesis,2 such as the use of [Co2(jU-alkyne)(CO)6] complexes in the synthesis of enediyne antitumor antibiotics.3-4... 

This review has already indicated numerous applications of dicobalt-alkyne complexes in organic synthesis. Like the Nicholas reaction (see Section II,D), the Pauson-Khand reaction has seen widespread use.175 This reaction is a three-component cycloaddition of alkynes with alkenes and carbon monoxide which occurs in the presence of octacarbonyldicobalt to afford cyclopentenones, as shown in Eq. (16). 

Pauson-Khand reaction cobalt-alkyne complexes in organic synthesis, 117... 

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