Arenes cross-coupling

Phenol-Arene Cross-Coupling and Nonsymmetrical Coupling Products... 

Kirste A, Schnakenburg G, Stecker F, Fischer A, Waldvogel SR (2010) Anodic phenol-arene cross-coupling reaction on boron-doped diamond electrodes. Angew Chem Int Ed 49 971-975... 

The formation of a C-C bond resulting from the coupling of two C-H bonds is a particularly attractive target, since the only formal by-product would be hydrogen, or water in an oxidative system. However, substantial hurdles impede the conception of a catalytic arene cross-coupling process that does not involve any substrate pre-activation at all. Aside from issues of reactivity and regioselectivity, the prevention of homo-coupling is a key factor for the development of this important class of reaction. The catalyst must be able to react with one arene in the first step of the catalytic cycle and then invert its selectivity in the second step to react exclusively with a different arene (Scheme 29). 

DeBoef and co-workers have reported a similar reaction, wherein direct C-H to C-H indole-arene cross-coupling can be controlled through the use of a particular oxidant (Scheme 34) [53,54], The basis of their selectivity concept is the formation of different polyvalent clusters between the Pd(OAc)2 and the AgOAc or Cu(0 Ac)2 oxidants respectively, and the subsequent reactivity of these complex in the aryla-tion reaction. The same group also demonstrated the utility of an intermolecular C-H to C-H coupling reaction. 

Stuart DR, Villemure E, Fagnou K (2007) Elements of regiocontrol in palladium-catalyzed oxidative arene cross-coupling. J Am Chem Soc 129 12072-12073... 

The selective electrochemical oxidation of one reaction partner gave rise to the first anodic phenol-arene cross-coupling (Scheme 4) [4]. The presence of additional water or methanol in the electrolyte turned out to be beneficial for the yield as well as selectivity [18]. In many cases, the ratio for the mixed biaryl (AB) vs. biphenyl (BB) exceeded 100 1. Since no leaving functionalities are required, simple starting materials can be employed, and the 1,1,1,3,3,3-hexafluoroisopropanol is almost quantitatively recovered. Biaryls 8-10 with different substitution patterns are feasible in good isolated yields. The transformation is compatible with a variety of functional groups and tolerates sulfide and tertiary alkyl moieties in the substrates. Compound 11 and 12 were the only observed mixed biaryls in the reaction mixture. Products originating... 

The oxidative coupling of thiophene, furan[338] and pyrrole[339,340] is also possible. The following order of reactivity was observed in the coupling of substituted furans[338] R = H > Me > CHO > CO Me > CH(OAc)i > CO2H. The cross-coupling of furans and thiophenes with arene is possible, and 4-phenylfurfural (397) is the main product of the cross-coupling of furfural and benzene[341]. 

Uemura M (2004) (Arene)Cr(Co)3 Complexes Cyclization,Cycloaddition and Cross Coupling Reactions. 7 129-156 Ujaque G, see Drudis-Sole G (2005) 12 79-107... 

Over the last decade, the chemistry of the carbon-carbon triple bond has experienced a vigorous resurgence [1]. Whereas construction of alkyne-con-taining systems had previously been a laborious process, the advent of new synthetic methodology based on organotransition metal complexes has revolutionized the field [2]. Specifically, palladium-catalyzed cross-coupling reactions between alkyne sp-carbon atoms and sp -carbon atoms of arenes and alkenes have allowed for rapid assembly of relatively complex structures [3]. In particular, the preparation of alkyne-rich macrocycles, the subject of this report, has benefited enormously from these recent advances. For the purpose of this review, we Emit the discussion to cychc systems which contain benzene and acetylene moieties only, henceforth referred to as phenylacetylene and phenyldiacetylene macrocycles (PAMs and PDMs, respectively). Not only have a wide... 

Another recent development in the field of palladium-catalyzed reactions with alkynes is a novel multicomponent approach devised by the Lee group. Starting from a-bromovinyl arenes and propargyl bromides, the assembly ofeight-membered car-bocycles can be realized via a cross-coupling/[4+4] cycloaddition reaction. The authors also presented the combination of a cross-coupling and homo [4+2], hetero [4+2], hetero [4+4] or [4+4+1] annulation leading to various cyclic products [147]. 

The synthesis of the second Stille coupling partner 34 was efficiently achieved in three steps. First, 2-bromojuglone (36) [28] was protected as its methoxymethyl ether (46, Scheme 3.7). The quinone was reduced using sodium thiosulfate, and the resulting hydroquinone was protected with methoxymethyl chloride to afford the arene 47. Finally, stannylation using tetrakis-(triphenylphosphine)palladium and hexabutylditin [29] afforded the cross-coupling partner 34 in high yield. 

Denmark pursued intramolecular alkyne hydrosilylation in the context of generating stereodefined vinylsilanes for cross-coupling chemistry (Scheme 21). Cyclic siloxanes from platinum-catalyzed hydrosilylation were used in a coupling reaction, affording good yields with a variety of aryl iodides.84 The three steps are mutually compatible and can be carried out as a one-pot hydro-arylation of propargylic alcohols. The isomeric trans-exo-dig addition was also achieved. Despite the fact that many catalysts for terminal alkyne hydrosilylation react poorly with internal alkynes, the group found that ruthenium(n) chloride arene complexes—which provide complete selectivity for trans-... 

Application in organic synthesis of pentacoordinated triorganodifluorosilicate anions, such as [Bu4N][Ph3SiF2] 825, have been extended to palladium(0)-catalyzed cross coupling reactions (solvents DMF, TFIF, dioxane) with arene halides (Scheme 111).825 This method is tolerant to various palladium(O) catalysts and provides excellent yields of mainly heterocoupled products and only small amounts of homocoupled byproducts. 

The corresponding catalytic version of this reaction was performed using either naphthalene- or biphenyl-supported polymers 594 or 595, respectively, which were prepared by cross-coupling copolymerization of 2-vinylnaphthalene or 4-vinylbiphenyl with vinyl-benzene and divinylbenzene promoted by AIBN in THF and polyvinyl alcohoP . These polymers have been used as catalysts (10%) in lithiation reactions involving either chlorinated functionalized compounds or dichlorinated materials in THF at —78°C and were re-used up to ten times without loss of activity, which is comparable to the use of the corresponding soluble arenes. 

Cycloalkanes R R R H and chelating arenes ArH were oxidatively cross-conpled to Ar R R R by [RuClj(p-cymene)]2/TBHP/135°C (the reactants were the solvent) thus 2-phenylpyridine and cyclo-octane were cross-coupled cf. mech. Ch. 1. Other complexes (Ru(acac)3, [RuCl CCOD)] and RuHj(CO)(PPh3)3) also catalysed the reaction [78]. 

Palladium(0)-catalyzed cross-coupling of aryl halides and alkenes (i.e., the Heck reaction) is widely used in organic chemistry. Oxidative Heck reactions can be achieved by forming the Pd -aryl intermediate via direct palladation of an arene C - H bond. Intramolecular reactions of this type were described in Sect. 4.1.2, but considerable effort has also been directed toward the development of intermolecular reactions. Early examples by Fu-jiwara and others used organic peroxides and related oxidants to promote catalytic turnover [182-184]. This section will highlight several recent examples that use BQ or dioxygen as the stoichiometric oxidant. 

---