Reductive coupling of carbonyls to alkenes

Reductive coupling of carbonyls to alkenes Titanium(IV) chloride-Zinc, 310 of carbonyls to pinacols Titanium(III) chloride, 302 Titanium(IV) chloride-Zinc, 310 of other substrates Samarium(II) iodide, 270 Reductive cyclization 2-(Phenylseleno)acrylonitrile, 244 Tributylgermane, 313 Tributyltin hydride, 316 Triphenyltin hydride, 335 Trityl perchlorate, 339 Reductive hydrolysis (see Hydrolysis) Reductive silylation Chlorotrimethylsilane-Zinc, 82... 

REDUCTIVE COUPLING OF CARBONYLS TO ALKENES ADAMANT YLIDENE AD AMANTANE... 

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). 

Reductive coupling of carbonyl compounds to dials. Activated Ti(0) (2, 368-369) effects the reductive coupling of carbonyl compounds to olefins and also converts 1,2-diols to alkenes (7, 368-369). Corey et al. employed this reagent for... 

The reductive coupling of carbonyl compounds, especially ketones, to give pinacols is an important method for the formation of vicinally functionalized C—C bonds. In addition, the related coupling of carbonyls to give alkenes, the McMurry reaction, provides a complementary route for C=C bond elaboration." ... 

Although the reduction of carbonyls to alcohols or hydrocarbons is well documented, no general method was available for the reductive coupling of carbonyl compounds directly to alkenes prior to the use of low-valent transition metals. The reductive coupling of carbonyl compounds by low-valent transition metals is now an important method for C=C bond formation, and has been widely reviewed." ... 

For a detailed discussion of the reductive coupling of carbonyl compounds to alkenes see Section 2.6.7. 

Z11-AICI3 in MeCN is reported for reductive coupling of carbonyl compounds to form alkenes. ... 

One of the most powerful methods for constructing a carbon-carbon bond is the reductive coupling of carbonyl compounds giving olefins and/or 1,2-diols [71]. Of these methods, the pinacol coupling [72], which was described in 1859, is still a useful tool for the synthesis of vicinal diols. The corresponding products of this reaction can be used as intermediates for the preparation of ketones and alkenes [73]. More importantly, this methodology has been applied to the synthesis of biologically active natural compounds [74]. 

Organotitanium and -zirconium chemistry already has an established place in organic synthesis and many reactions are covered elsewhere in the Practical Approach series. Examples include reductive coupling of carbonyl compounds with low valent titanium to form 1,2-diols or alkenes methylenation of ester carbonyl groups with titanocene methylidene (Cp2Ti=CH2) zirconium-catalysed methylalumination of alkynes and hydrozirconation of alkynes and alkenes with the Schwartz reagent, Cp2ZrHCl. ... 

Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen... 

Ihmels H, Otto D (2005) Intercalation of Organic Dye Molecules into Double-Stranded DNA - General Principles and Recent Developments. 258 161-204 Iida H, Krische MJ (2007) Catalytic Reductive Coupling of Alkenes and Alkynes to Carbonyl Compounds and Imines Mediated by Hydrogen. 279 77-104 Imai H (2007) Self-Organized Formation of Hierarchical Structures. 270 43-72 Indelli MT, see Chiorboli C (2005) 257 63-102 Inoue Y, see Borovkov VV (2006) 265 89-146 Ishii A, Nakayama J (2005) Carbodithioic Acid Esters. 251 181-225 Ishii A, Nakayama J (2005) Carboselenothioic and Carbodiselenoic Acid Derivatives and Related Compounds. 251 227-246... 

The Pauson-Khand reaction gives the same product as the group 4 metal-mediated reductive coupling and carbonylation, and both reactions proceed by essentially the same mechanism formation of an alkyne-metal tt complex, insertion of an alkene, insertion of CO, and reductive elimination. Some details differ, however. When an alkyne is added to Co2(CO)g, CO evolves, and an isolable, chromatographable alkyne-Co2(CO)6 complex is obtained. This butterfly complex contains four Co(II)-C bonds, and the Co-Co bond is retained. The formation of the alky n e-C o2 (C O) 6 complex involves the formation of an ordinary tt complex of the alkyne with one Co(0) center, with displacement of CO. The tt complex can be written in its Co(II) cobaltacyclopropene resonance structure. The tt bond of the cobaltacyclopropene is then used to form a tt complex to the other Co center with displacement of another equivalent of CO. This second tt complex can also be written in its cobaltacyclopropene resonance structure. The alkyne-Co2(CO)6 complex has two 18-electron Co(II) centers. 

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