Hydroacylation of olefins

A recyclable system for the directed rhodium-catalyzed hydroacylation of olefins was reported using a homogeneous phenol and 4,4 -dipyridyl solvent system at 150 °C. High yields were obtained even after eight cycles and the ketone product was obtained after decantation (Equation (132)).115... 

Based on Watanabe s intermolecular hydroacylation of olefins with aldehydes,348 Kondo and Misudo developed the first ruthenium-catalyzed hydroacylation of 1,3-dienes with aldehydes (Scheme 71). Usually, palladium-mediated hydroacylations of 1,3-dienes with aldehydes give tetrahydropyran and/or open-chain homoallylic alcohol derivatives.350 However, in the present ruthenium-catalyzed transformations, the corresponding /3,7-unsaturated... 

Rhodium( )-Catalyzed Asymmetric Hydroacylation of Olefins and Alkynes with Aldehydes I 85... 

Loupy, A., Chatti, S., Delamare, S., Lee, D.Y., Chung, J.H. and Jun, G.H., Solvent-free chelation-assisted hydroacylation of olefin by rhodium(I) catalyst under microwave irradiation, /. Chem. Soc., Perkin Trans. 1, 2002, 1280-1285. 

The hydroacylation of olefins with aldehydes is one of the most promising transformations using a transition metal-catalyzed C-H bond activation process [1-4]. It is, furthermore, a potentially environmentally-friendly reaction because the resulting ketones are made from the whole atoms of reactants (aldehydes and olefins), i.e. it is atom-economic [5]. A key intermediate in hydroacylation is a acyl metal hydride generated from the oxidative addition of a transition metal into the C-H bond of the aldehyde. This intermediate can undergo the hydrometalation ofthe olefin followed by reductive elimination to give a ketone or the undesired decarbonyla-tion, driven by the stability of a metal carbonyl complex as outlined in Scheme 1. 

The use of C-H bonds is obviously one of the simplest and most straightforward methods in organic synthesis. From the synthetic point of view, the alkylation, alkenylation, arylation, and silylation of C-H bonds are regarded as practical tools since these reactions exhibit high selectivity, high efficiency, and are widely applicable, all of which are essential for practical organic synthesis. The hydroacylation of olefins provides unsymmetrical ketones, which are highly versatile synthetic intermediates. Transition-metal-catalyzed aldol and Michael addition reactions of active methylene compounds are now widely used for enantioselective and di-astereoselective C-C bond formation reactions under neutral conditions. 

Lenges CP, Brookhart M. Co(I)-catalyzed inter- and intramolecular hydroacylation of olefins with aromatic aldehydes. J Am Chem Soc 1997 119(13) 3165—3166. 

For the intermolecular hydroacylation of olefins and acetylenes, ruthenium complexes - as well as rhodium complexes - are effective [60-64]. In 1980, Miller reported the first example of an intermolecular hydroacylation of aldehydes with olefins to give ketones, during their studies of the mechanism of the rhodium-catalyzed intramolecular cydization of 4-pentenal using ethylene-saturated chloroform as the solvent [60]. A similar example of the hydroacylation of aldehydes with olefins using ruthenium catalyst is shown in Eq. 9.43. When the reaction of propionaldehyde with ethylene was conducted in the presence of RuCl2(PPh3)3 as the catalyst without... 

Tischchenko-type dimerization of aldehyde is catalyzed by dihydridorutheni-um(II) complexes. In this reaction, aldehyde is initially consumed to reduce Ru(II) to give Ru(0), to which aldehyde oxidatively adds to give a hydrido(acyl)mtheni-um(II) active intermediate affording esters [15]. Hydroacylation of olefins [16] and dienes [17] is also catalyzed by ruthenium complexes (Scheme 14.5). 

The method of transition metal induced hydroacylation of olefins with aldehydes has its origins in the observation that aldehydes are decarbonylated by Wilkinson s catalyst31. Mechanistically, decarbonylation is believed to start with an oxidative addition of a low valent transition metal unit to the aldehyde C —H bond. This individual step has been observed in several cases32 " 37. The resulting metal acyl hydride system can then be decarbonylated to form a new C - H bond upon reductive elimination, steps which are also well known. 

A New Solvent System for Recycling Catalysts for Chelation-Assisted Hydroacylation of Olefins with Primary Alcohols [26]... 

The intramolecular hydroacylation of olefins typically occurs in higher yields than the intermolecular hydroacylation of olefins. In its simplest form, the reaction of 4-pentenone in the presence of stoichiometric amoimts of V 5Udnson s catalyst at room temperature in ethylene-saturated solvent formed the isomeric cyclopentanone in good yield after long reaction times (Equation 18.86). Many different cyclopentanones were prepared by related methods. " ... 

A new rhodium-based hydroacylation of olefins has been developed recently. Insertion of an olefin into the rhodium-hydride bond of complex CXLVin gives the alkyirhodium complex CXLIX, which on interaction with acyl halides produces the ketonic products through the acylalkylrhodium(III) intermediate (CX,) (Schwartz and Cannon, 1974). 

Hydroacylation of olefins to yield ketones can be achieved by the addition of an aldehyde in the presence of a silver salt or by the addition of an aldimine (29) in the presence of a rhodium(i) catalyst [equation (5)]. ... 

Chelation-assisted hydroacylation of olefins with aliphatic aldehydes possesses an intrinsic problem associated with competitive formation of aldol condensation products. A cooperative C-C double bond cleavage process has been developed as a solution to this problem [36]. For example, hydroacylation reactions of aliphatic... 

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