Alkenes transition metal-catalyzed

From Other Alkenes-Transition Metal Catalyzed Cross-Coupling and Olefin... 

Olefin metathesis is the transition-metal-catalyzed inter- or intramolecular exchange of alkylidene units of alkenes. The metathesis of propene is the most simple example in the presence of a suitable catalyst, an equilibrium mixture of ethene, 2-butene, and unreacted propene is obtained (Eq. 1). This example illustrates one of the most important features of olefin metathesis its reversibility. The metathesis of propene was the first technical process exploiting the olefin metathesis reaction. It is known as the Phillips triolefin process and was run from 1966 till 1972 for the production of 2-butene (feedstock propene) and from 1985 for the production of propene (feedstock ethene and 2-butene, which is nowadays obtained by dimerization of ethene). Typical catalysts are oxides of tungsten, molybdenum or rhenium supported on silica or alumina [ 1 ]. 

Transition metal-catalyzed carbenoid transfer reactions, such as alkene cyclopro-panation, C-H insertion, X-H insertion (X = heteroatom), ylide formation, and cycloaddition, are powerful methods for the construction of C-C and C-heteroatom bonds [1-6]. In contrast to a free carbene, metallocarbene-mediated reactions often proceed stereo- and regioselectively under mild conditions with tolerance to a wide range of functionalities. The reactivity and selectivity of metallocarbenes can be... 

Aziridines are versatile intermediates in organic synthesis and commonly found in bioactive molecules. The transition metal-catalyzed nitrene transfer to alkenes is an attractive method for the synthesis of aziridines [7]. In 1984, Mansuy and coworkers reported the first example of an iron-catalyzed alkene aziridination in which iron porphyrin [Fe(TTP)Cl] was used as catalyst and PhINTs was used as nitrene source [30]. Subsequently, the same authors demonstrated that [Fe(TDCPP) (CIO4)] is a more efficient and selective catalyst than [Fe(TTP)Cl] (Scheme 20). 

Although a maximum of 6 turnovers in 3 days (TOP = 0.08 h ) were reached before loss of activity, this is the first successful demonstration of hydroamination of an alkene via a transition metal-catalyzed N-H activation process. 

Transition Metal-Catalyzed Epoxidation of Alkenes. Other transition metal oxidants can convert alkenes to epoxides. The most useful procedures involve f-butyl hydroperoxide as the stoichiometric oxidant in combination with vanadium or... 

Transition metal-catalyzed transformations are of major importance in synthetic organic chemistry [1], This reflects also the increasing number of domino processes starting with such a reaction. In particular, Pd-catalyzed domino transformations have seen an astounding development over the past years with the Heck reaction [2] - the Pd-catalyzed transformation of aryl halides or triflates as well as of alkenyl halides or triflates with alkenes or alkynes - being used most often. This has been combined with another Heck reaction or a cross-coupling reaction [3] such as Suzuki, Stille, and Sonogashira reactions. Moreover, several examples have been published with a Tsuji-Trost reaction [lb, 4], a carbonylation, a pericyclic or an aldol reaction as the second step. 

A few years later, the same group extended this strategy in order to access metabolically stable C-glycosyl clusters containing long-arm spacers via a sequence of transition metal-catalyzed transformations (Scheme 11).93 In this context, crossmetathesis reactions of various C-glycosyl compounds with alkenes having available... 

For comprehensive reviews of transition-metal-catalyzed alkene polymerization, see Chem. 

Various transition metal complexes, in particular of late transition metals, were reported to be effective catalysts for such double bond isomerization. Because organic synthesis is the focus of this volume, this section will cover the transition metal-catalyzed isomerization of alkenes, which has the significant synthetic and industrial utilities. This chapter will also include the synthetic application, asymmetric reactions,4-6 and isomerization of alkynes, in particular, that of propargylic alcohols. 

In addition to alkenes and alkynes, allenes have attracted considerable interest due to their unique reactivity and multireaction sites. Therefore, transition-metal-catalyzed nucleophilic addition reaction of amines and imines to allenes has been extensively studied to prepare biologically important amines and nitrogen-heterocycles.31,31d... 

Mechanism of Transition Metal-Catalyzed Hydrosilylation of Alkenes 815... 

This landmark discovery paved the way for the development of transition metal-catalyzed hydroboration. The conversion of an alkene into an organoborane intermediate has made this a valuable synthetic technique, particularly since the development of enantioselective variants.9,10 They serve as synthons for numerous functional groups11 and are often subjected to a consecutive carbon-oxygen, carbon-carbon, boron-carbon, boron-chlorine, or carbon-nitrogen24 bond-forming reaction (Scheme 3). 

While transition metal-catalyzed hydroboration is a well-established reaction, the same cannot be said for the transition metal-catalyzed hydroalumination. The synthetic utility of this reaction is only just beginning to emerge. Lautens has led the way in the use of hydroaluminations as the key step in the total synthesis of complex natural products. The synthesis of the anti-depressant sertraline130 involved the formation of the tetrahydronaphthalene core, and this is best achieved using the nickel-catalyzed hydroalumination of oxabicyclic alkenes (Table 16). 

The use of ionic liquids has been successfully studied in many transition metal-catalyzed hydrogenation reactions, ranging from simple alkene hydrogenation to asymmetric examples. To date, almost all applications have included procedures of multiphase catalysis with the transition-metal complex being immobilized in the ionic liquid by its ionic nature or by means of an ionic (or highly polar) ligand. 

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. 

---