Catalytic methods metal-catalysed synthesis

Although a metal catalysed decomposition of ethyl diazoacetate was originally described by Silberrad and Roy in 19061, it was to be many years before the value of this type of process for cyclopropanation of alkenes using transition metal catalysts was widely appreciated and reliable, efficient methods were developed. By the early 1960s, the reaction had become important in organic synthesis. Various transition metal compounds have been screened for catalytic cyclopropanation. Copper, rhodium and palladium compounds have... 

While several metal-catalysed approaches to solve the task of generating fl tz-l,2-diols have been developed, this method remains remarkable, since it represents the first small molecule-catalysed, catalytic version of this transformation. The starting materials do not need activation or protection, and the reaction can be performed under standard conditions without further precautions. The selectivity of the reaction potentially results from a hydro Q acetone enamine-initiated transition state (5). More recently, Enders et al. applied a related method to the organocatalytic synthesis of sialic acid precursors (Scheme 5.6). Protected pyruvic aldehyde (6) was reacted with several aldehydes, forming the desired aldols (7) in moderate yields, but good selectivities (31-51%, 90-92% de, 73-99% ee). The conditions were optimised to limit detrimental side reaetions sueh as Mannich elimination or formation of the aeetal self-aldolisation produet. While generally easily applicable and robust, the method laeks effieiency in one key parameter, its reaction time. This limitation, combined with moderate yields unfortunately prevents a scale-up to or beyond the pilot plant. 

The development of methods for the catalytic enantioselective formation of C-Si bonds is an important challenge in organic synthesis [114], In this context, the transition metal-catalysed enantioselective conjugate addition (ECA) of in situ-generated Si nucleophiles derived from readily available sources [e.g. Cl2PhSi-SiMes and Me2PhSi-B(Pin)] to a,p-misaturated acceptors with a substituent in the... 

Catalytic aminocarbonylation provides an extremely useful method for the regioselective synthesis of amides by the use of CO and NH3 or an amine. The variety of catalysts and substrates that can be used to achieve amide products is ever increasing. For a thorough overview of metal catalysed aminocarbonylations a review by Cribble is available. ... 

A review of recent advances in transition-metal-catalysed oxidations by molecular oxygen has highlighted the scope and limitations, as well as the meehanisms of these reactions. " " An overview of the fundamental studies on a new method of synthesis of nicotinic acid by the gas-phase catalytic oxidation of -picoline by oxygen has been presented. The reactivity of vanadium species has been considered in order to discover the nature of the active catalyst. Kinetic equations for -picoline oxidation on vanadia-titania catalysts have been discussed. " The effect of quaternary ammonium salts or macrocyclic ethers on the autoxidation of ethylbenzene or the decomposition of the a-phenylethyl hydroperoxide intermediate catalysed by Ni(II) or Fe(III) acetylacetonates has been reviewed. ... 

The methods of synthesis of uronic acids by catalytic and nonspecific oxidation of sugars has been reviewed,and a study of the oxidation of octyl a-D-glucopyranoside to octyl a-o-glucopyranosiduronic acid by sodium hypobromite catalysed by some ruthenium complexes has been reported. The stability constants of metal ion-uronic acid complexes have been reviewed. ... 

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