Metal catalyzed addition

The uncatalyzed addition of hydrogen to an alkene, although exothermic, is very slow. The rate of hydrogenation increases dranatically, however, in the presence of certain finely divided metal catalysts. Platinum is the hydrogenation catalyst most often used, although palladium, nickel, and rhodium are also effective. Metal-catalyzed addition of hydrogen is normally rapid at room temperature, and the alkane is produced in high yield, usually as the only product. 

Because organophosphorus compounds are important in the chemical industry and in biology, many methods have been developed for their synthesis [1]. This chapter reviews the formation of phosphorus-carbon (P-C) bonds by the metal-catalyzed addition of phosphorus-hydrogen (P-H) bonds to unsaturated substrates, such as alkenes, alkynes, aldehydes, and imines. Section 5.2 covers reactions of P(lll) substrates (hydrophosphination), and Section 5.3 describes P(V) chemistry (hydrophosphorylation, hydrophosphinylation, hydrophosphonylation). Scheme 5-1 shows some examples of these catalytic reactions. 

Phosphine itself as well as primary and secondary phosphines undergo metal-catalyzed additions to olefins and formaldehyde. More than 40 years ago, some Ger-... 

In comparison to related P(III) chemistry, metal-catalyzed additions of P-H bonds in P(V) compounds to unsaturated substrates have been studied in more detail, and several synthetically useful processes have been developed. In particular, the use of heterobimetallic BINOL-based catalysts allows asymmetric hydrophosphonylation of aldehydes and imines in high yield and enantiomeric excess. 

Metal-catalyzed additions of P(III)-H and P(V)-H bonds to unsaturated substrates have been studied much less than related additions of, for example, B-H or Si-H bonds [36]. Already, some synthetically useful processes have been developed, and further work is likely to produce additional useful transformations as well as more fundamental information on the mechanisms of these reactions. 

To my knowledge, the first clear example of a transition metal-catalyzed addition of a thiol to a carbon-carbon unsaturated compound, hydrothiolatiori, was reported by Dzhemilev et al. in 1981 (Eq. 7.8) [20],... 

Although the path (a) has been verified by a stoichiometric reaction [23], the details of exact reaction mechanism remain unsettled. Triggered by this publication [and the Pd-catalyzed doublethiolation of alkynes described in Eq. (7.7) in Section 7-3], a number of transition metal-catalyzed additions of S-X or Se-X bonds to C-C unsaturated organic compounds started to be published. In 1994, BackvaU et al. applied the Pd(OAc)2-catalyzed hydrothiolation to conjugated enynes and obtained 17,... 

In this section we will survey the use of transition metal-catalyzed additions, at times accompanied by rearrangement processes, that lead to the generation of new carbon-phosphorus bonds. 

Han, L.-B. and Tanaka, M. Transition metal-catalyzed addition reactions of H-heteroatom and inter-heteroatom bonds to carbon-carbon unsaturated linkages via oxidative additions, Chem. Commun., 395, 1999. 

Transition Metal-catalyzed Additions of Oxygen Nucleophiles to Alkynes 672... 

The transition metal-catalyzed addition of nucleophiles to alkynes is a broad field that has been studied extensively... 

The synthesis of alcohols, ethers, and ketones by metal-catalyzed addition of water or alcohols to alkenes and alkynes is a well-established reaction in organic chemistry. Many regio- and stereoselective modifications of these reactions are known. In contrast, the analogous addition of ammonia or primary and secondary amines to nonactivated alkenes and alkynes has not had a comparable development, in spite of extensive efforts. In this section, we summarize the recent results of amination to unsaturated compounds. 

Metal catalysts, 10 46-47 Metal-catalyzed addition, polymers prepared by, 15 179-180 Metal chelation, 9 424 Metal chloride salts, 13 817-818 Metal chlorides, decomposition by acids, 13 822-824 Metal cleaning... 

Synthesis of Phosphonium Salts by Metal-Catalyzed Addition Reaction... 

Phosphonium salts can be synthesized by the transition-metal-catalyzed addition reaction of triaryphosphines and acids to unsaturated compounds. The reaction of PPh3, CH3SO3H, and alkynes in the presence of a palladium or rhodium catalyst gave alkenylphosphonium salts. Although Pd(PPh3)4 directed the C-P bond formation at the internal carbon atom of aliphatic 1-alkynes (Markovnikov mode), [RhCl(cod)]2... 

In general, transition metal-catalyzed addition reactions to 1,3-dienes gave 1,4-adducts via 7t-allyl metal intermediates.23 The ar //-Markovnikov 1,2-addition mode of this reaction is therefore unusual (Scheme 17). It was noted that the configuration of the 3-olefin was retained with either ( )- or (Z)-1,3-dienes. The observation that the 3-olefin was unimportant for this reaction strongly suggests that the method could be applicable to unactivated alkenes. 

Transition Metal-Catalyzed Addition/Cycloaddition of Allenes 925... 

Transition Metal-Catalyzed Addition/Cydoaddition of Allenes... 

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