Transition metal catalysis intermolecular

The crossover product, propionaldehyde-l,3-d-3- C 12, clearly demonstrated that the isomerization occurred via intermolecular 1,3-hydrogen shift. These results are consistent with a modified metal hydride addition-elimination mechanism which involves exclusive 1,3-hydrogen shift through oxygen-directed Markovnikov addition of the metal hydride to the carbon-carbon double bond (Scheme 12.2). The directing effect of functional groups on the selectivity of transition metal catalysis is well presented [9], and an analogous process appears to be operative in the isomerization of allylamines to enamines [10]. 

Over the last decade, the copper-mediated or copper-catalyzed C-H functionalization has been developed rapidly and greatly by significant efforts of many researchers, and cheap and abundant copper salts now can replace, to some extent, precedented noble transition metal catalysts such as Pd, Rh, and Ru. Moreover, some unique features of copper salts and complexes are observed. The intermolecular dehydrogenative cross-couplings mentioned in this chapter are such good examples, and they are otherwise challenging even under known noble transition metal catalysis. However, there is still a large room for further... 

Abstract The present work describes a comprehensive review of the functionalization of cyclopropyl C-H bonds via transition-metal catalysis. Compared to the enormous number of publications related to direct sp and sp bond transformations in the last two decades, the first full account of direct cyclopropyl C(sp )-H bond functionalization was only disclosed in 2011. Both intra- and intermolecular transformations are detailed in the review, including asymmetric reactions. In addition, mechanistic aspects of various Pd-catalyzed cyclopropane functionalizations are discussed. 

Methods for lactone synthesis by transition metal catalysis involving C—O formation developed over the past 50 years have demonstrated much promise. Indeed, lactones have inspired the discovery of new organometallic transformations, design of metal catalysts, and detailed understanding of reaction mechanisms. Issues of waste minimization and stereoselectivity have been addressed. Future developments for chiral lactone synthesis will likely focus on establishing efficient transformations with broad scope and application in complex molecule total synthesis, especially in regards to macrolactonization where entropic costs often plague intramolecular reactivity with undesired intermolecular reactions. 

Strict intermolecular diamination of alkenes remains a difficult process in transition-metal catalysis. Still, some interesting reactivity has recently been uncovered for terminal alkenes [122-124]. First, Shi reported the development of diamination of styrenes 18 and 179 under copper catalysis (Scheme 16.49). These protocols make use of three diaziridine derivatives 180-182, which were used as... 

Direct catalytic intermolecular a-allylic alkylation of aldehydes and cyclic ketones has been achieved using a one-pot combination of a transition metal catalyst, Pd(PPh3)4, and an organocatalyst a secondary amine which facilitates enamine catalysis.300... 

Direct formation of isolable cr-aryl complexes by intermolecular oxidative addition of an aromatic C—H bond to a transition-metal complex was first observed in an alkyl phosphine complex of Ru and has now been extended to most of the transition metals. The relevant literature is summarized in Table 1. There are reviews of C—H activation by homogeneous metal complexes and its relevance to homogeneous and heterogeneous catalysis s " . 

Examples in which the cation of the ionic liquid contains the transition metal complex for catalysis have also been published. For example, Forbes and coworkers [63] synthesized a Rh-containing ionic liquid cation by replacing an acetate ligand at the Rh center by a carboxyhc acid functionalized imidazolium moiety. The modified dirhodium(ii) dimer of this kind was applied as an effective catalyst in the intermolecular cydopropanation reaction of styrene using ethyl diazoacetate. 

Both oxidative addition and a-bond metathesis are core subjects of organo-transition metal chemistry and catalysis. They also provide the unique regioselective intermolecular alkane activation modes at the terminal (less substituted) C atom contrary to radical-type and cationic C-H activation (see Chap. 19). 

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