Organic synthesis metal-catalyzed transformation

Transition metal-catalyzed transformations of organosil-icon compounds continue to make important contributions to organic synthesis and hold great promise for developing efficient routes to Si-based functional materials. The need to understand the mechanisms of these transformations and develop new methodologies has inspired researchers to probe the fundamental reactivities of silanes with a variety of transition metal complexes. The reactivities of Ni complexes with hydrosilanes have been studied quite vigorously and a number of interesting transformations have been reported recently, some of which are described below. 

Substituted vinylsilanes such as ,Z-RCH=CHSiR 3 and R(SiR 3)C=CH2 are a class of organosilicon compounds commonly used in organic synthesis. Many efficient stereo- and regio-selective methodologies for the synthesis of substituted vinylsilanes involving classical stoichiometric routes from organometallic reagents and, more recently, transition metal-catalyzed transformations of alkynes, silylalkynes, alkenes, and simple vinylsilanes have been reported [1-3]. 

Organocatalysis has emerged as a powerful synthetic paradigm that is complementary to metal-catalyzed transformations and has fadhtated the development of new methods to make various chiral molecules [1, 2]. It has also attracted great interest in organic chemistry for its potential applications in total synthesis [3],... 

The insertion of unsaturated molecules into metal-carbon bonds is a critically important step in many transition-metal catalyzed organic transformations. The difference in insertion propensity of carbon-carbon and carbon-nitrogen multiple bonds can be attributed to the coordination characteristics of the respective molecules. The difficulty in achieving a to it isomerization may be the reason for the paucity of imine insertions. The synthesis of amides by the insertion of imines into palladium(II)-acyl bonds is the first direct observation of the insertion of imines into bonds between transition metals and carbon (see Scheme 7). The alternating copolymerization of imines with carbon monoxide (in which the insertion of the imine into palladium-acyl bonds would be the key step in the chain growth sequence), if successful, should constitute a new procedure for the synthesis of polypeptides (see Scheme 7).348... 

Metal-catalyzed enantiose-lective reactions are used in the synthesis of complex organic molecules. These transformations offer cost-effective, highly selective alternatives to the more classical methods. Additional levels of efficiency are achieved when various catalytic reactions are used successively. 

It is well known that oxidation of carbamates leads to the formation of N-acyliminium ions via dissociation of the C-H bond a. to nitrogen. The electrochemical,4 metal-catalyzed,5 and chemical methods6 have been reported in the literature to accomplish this transformation. The transformation serves as a useful tool for organic synthesis, although only compounds of high oxidation potentials such as methanol and cyanide ion can be used as nucleophile. It... 

Transition metal-catalyzed carbocycUzation reactions of tethered diene, enyne, diyne, and vinylallene derivatives represent an important class of transformations in synthetic organic chemistry. This may be attributed to the abihty to significantly increase molecular complexity through the highly selective combination of acyclic components, thereby facilitating the synthesis of complex polycychc products. Recently, rhodium-catalyzed carbocyclization reactions have attracted significant attention due to their immense synthetic versatility and the unique selectivities observed over a range of different transformations. This chapter provides an account of recent developments in rhodium-catalyzed [4-1-2] and [4-i-2-t2] carbocyclization reactions. 

The metal-catalyzed decomposition of diazo compounds has broad applications in organic synthesis [1-8]. Transient metal carbenoids provide important reactive intermediates that are capable of a wide variety of useful transformations, in which the catalyst dramatically influences the product distribution [5]. Indeed, the whole field of diazo compound decomposition was revolutionized in the early 1970s with the discovery that dirhodium tetracarboxylates 1 are effective catalysts for this process [9]. Many of the reactions that were previously low-yielding using conventional copper catalysts were found to proceed with unparalleled efficiency using this particular rhodium catalysis. The field has progressed extensively and there are some excellent reviews describing the breadth of this chemistry [5, 7, 10-17]. 

Alkaline earth metal oxides have been used as solid base catalysts for a variety of organic transformations. Excellent reviews by Tanabe 4) and Hattori 2,3,7) provide detailed information about the catalytic behavior of alkaline earth metal oxides for several organic reactions of importance for industrial organic synthesis. In this section, we describe in detail reactions that have been reported recently to be catalyzed by alkaline earth metal oxides. 

The transition metal-catalyzed addition of the Si-H bond of a hydrosilane across a C=C or C=C bond is a transformation of considerable importance in both large-scale industrial processes and in small-scale organic synthesis.Perhaps the most common industrial application of catalytic hydrosilylation is the platinum-catalyzed cross-linking of vinylsilane polymers with hydrosilanes. The interest in catalytic hydrosilylation in organic synthesis... 

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