Transition Metal-catalyzed Addition Reaction

This bisselenation might proceed via oxidative addition of (PhSe)2 to low-valent palladium complexes, regioselective selenopalladation of alkynes to give vinylic palladium intermediates, and reductive elimination of the vicinal diselenoalkenes with regeneration of the catalyst. 

The hydroselenation of alkynes with PhSeH also provides a simple route to 

Sequential addition/isomerization occurs in the presence of PdCl2(PhCN)2, affording internal vinyhc selenides selectively in good yields. 

Palladium complexes such as Pd(PPh3)4, Me2Pd(PPh5)3, and Pd(PPh),)2-(CH2=CH2) efficiently catalyze addition of O,O,Se-triphenyl phosphoroselenoate (PhSeP(O)(OPh)2), which bears an Se-P linkage, to terminal alkynes to produce the corresponding selenophosphorylation products, (Z)-l-(diphenoxyphosphinyl)-2- 

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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. 

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. 

Such an approach necessitates two additional synthetic operations introduction as well as removal of the reagent-directing group. However, such a disadvantage at first sight should be acceptable if one could solve a selectivity problem for a synthetically valuable reaction which is otherwise not susceptible to stereocontrol. In this context transition metal catalyzed addition reactions have gained importance as a consequence of their intrinsic atom economy and efficiency which may be beneficial for enviromental and economic grounds [2],... 

There are transition-metal catalyzed addition reaction of alkyl units to alkenes, often proceeding with metal hydride elimination to form an alkene. An intramolecular cyclization reaction of an A-pyrrolidino amide alkene was reported using an iridium catalyst for addition of the carbon ot to nitrogen to the alkene unit. OS I, 229 IV, 665 VII, 479. 

In the past decade, various kinds of transition-metal-catalyzed addition reactions of main group... 

This section deals with C-C bond forming asymmetric transition metal catalyzed addition reactions to double bonds. The material is divided into hydrocarboration, dicarboration and heterocarboration reactions. 

Besides stereoselectivity requirements, transition metal catalyzed addition reactions pose several other selectivity problems. Thus, regioselectivity must be achieved with unsymmetrical addends and isomerization of substrates and products, such as double-bond isomerization or epimerization of stereogenic centers, must be suppressed. Manipulation of catalytic systems might not only influence catalytic activities but also disturb a rather delicate reaction control and thus lead to different product selectivities. 

It has been shown that the stereochemistry of the hydrosilylation of 1-aUcynes giving 1-silyl-l-alkenes depends on the catalysts or promoters used. For example, the reactions under radical conditions give the cis-product predominantly via trans-addition , while the platinum-catalyzed reactions afford the trans-product via exclusive cts-addition. In the reactions catalyzed by rhodium complexes, thermodynamically unfavorable c/s-1-silyl-l-alkenes are formed via apparent trans-addition as the major or almost exclusive product. Since the trans-addition of HSiEts to 1-alkynes catalyz by RhCl(PPh3)3 was first reported in 1974 , there have been controversy and dispute on the mechanism of this mysterious trans-addition that is vray rare in transition-metal-catalyzed addition reactions to aUtynes. Recently, iridium 4i6 mthenium complexes were also found to give the ds-product with extremely high selectivity (vide supra). 

Liao, Y.-X., Xing, C.-H., Israel, M., Hu, Q.-S. (2011). Sequential aldol condensation-transition metal-catalyzed addition reactions of aldehydes, methyl ketones, and arylboronic acids. Organic Letters, 13, 2058-2061. 

As organosulfur compounds have been widely believed to be catalyst poisons, examples of the transition metal catalyzed reaction of these sulfur compounds have been limited. After the development of transition metal catalyzed addition of organosulfur compounds such as disulfides and thiols to carbon-triple bonds [9], many types of transition metal catalyzed addition reactions of organosulfur compounds have been developed. As to allenes, for example, the addition of thiols to terminal allenes successfully proceeds regioselectively at the internal double bonds of the allenes by the action of palladium acetate catalyst [10a,10b], while the disulfide addition to terminal allenes takes place at the terminal double bond in the presence of tetrakis (triphenylphosphine) palladium catalyst (Scheme 11.6) [10c]. 

Tanaka M (2012) Recent progress in transition metal-catalyzed addition reactions of H-P(O) compounds with unsaturated carbon linkages. Top Organomet Chem. doi 10.1007/ 3418 2011 20... 

Recent Progress in Transition Metal-Catalyzed Addition Reactions of H-P(O) Compounds with Unsaturated Carbon Linkages... 

In the transition-metal-catalyzed addition reactions of thiols to terminal alkynes, several addition products, i.e., Markovnikov-type adduct 1, Markovnikov addition and then double-bond-isomerization product 2, a n -Markovnikov adduct 3, double hydrothiolation product 4, and bisthiolation product 5, may be formed (Scheme 2). Controlling the product selectivity can be attained by the selection of transition metal complexes as catalysts, the use of additives, and/or the optimization of the reaction conditions (solvent, temperature, molar ratios of the starting materials, and so on). 

Although the present review deals with transition-metal-catalyzed addition reactions, we would like to point out that recent development of organocatalysis made it a very efficient tool for facilitating P-H bond addition reactions. As a selected representative examples we can mention hydrophosphination of... 

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