Coupling reductive carbonyl

Alkene-C=X (X=0, NR) Coupling (Reductive Carbonyl-Ene and Reductive Hydroacylation)... 

Reductive coupling of carbonyl compounds to yield olefins is achieved with titanium (0), which is freshly prepared by reduction of titanium(III) salts with LiAIH4 or with potassium. The removal of two carbonyl oxygen atoms is driven by T1O2 formation- Yields are often excellent even with sensitive or highly hindered olefins. (J.E. McMurry, 1974, 1976A,B). 

Among the appHcations of lower valent titanium, the McMurry reaction, which involves the reductive coupling of carbonyl compounds to produce alkenes, is the most weU known. An excellent review of lower valent titanium reactions is available (195). Titanium(II)-based technology is less well known. A titanium(II)-based complex has been used to mediate a stetio- and regio-specific reduction of isolated conjugated triple bonds to the corresponding polyenes (196). 

Catalytic Reductive Coupling of Carbonyl Compounds -The Pinacol Coupling Reaction and Beyond... 

Hirao T (2007) Catalytic Reductive Coupling of Carbonyl Compounds - The Pinacol Coupling Reaction and Beyond. 279 53-75 Hirayama N, see Sakai K (2007) 269 233-271 Hirst AR, Smith DK (2005) Dendritic Gelators. 256 237-273 Holzwarth AR, see Balaban TS (2005) 258 1-38... 

Table III. Reductive Coupling of Carbonyls with Zinc and Trimethylchlorosilane...

For a review encompassing the transition metal-catalyzed reductive coupling of carbonyl compounds, see Avalos, M. Babiano, R. Gintas, P. ... 

It is worth mentioning that some precursors easily catalyze the reductive carbonylation of alkynes from the C0/H20 couple. Here, the main role of water is to furnish hydrogen through the water-gas-shift reaction, as evidenced by the co-production of CO2. In the presence of Pd /KI terminal alkynes have been selectively converted into furan-2-(5H)-ones or anhydrides when a high concentration in CO2 is maintained. Two CO building blocks are incorporated and the cascade reactions that occur on palladium result in a cyclization together with the formation of an oxygen-carbon bond [37,38]. Two examples are shown in Scheme 4. 

TABLE 5.8. Corey s reductive coupling of carbonyl compounds... 

McMurry, J. E., and M. P. Fleming. 1974. A new method for the reductive coupling of carbonyls to olefins Synthesis of /3-carotene. J. American Chemical Society 96 4708-9. 

Benzene hydrocarbons are known to undergo radical coupling reactions and the intramolecular reductive coupling of carbonyl compounds with a benzene ring has been achieved. Best conditions for this process are at a tin cathode with isopropanol solvent and tetaethylammonium tosylate as supporting electrolyte [102, 103], The reaction is performed at constant current in a divided cell. A single stereoiso-... 

Another possibility for creating a new ligand structure is to connect two phos-phaferrocene molecules via their formyl functional groups. The reductive coupling of carbonyl compounds with low-valent Ti reagents - the McMurry reaction - is a technique that has found wide application in organic synthesis [18]. 

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