Ruthenium-catalysed reactions coupling

Aspley CJ, Williams JAG (2001) Palladium-catalysed cross-coupling reactions of ruthenium bis-terpyridyl complexes strategies for the incorporation and exploitation of boronic acid functionality. New J Chem 25 1136... 

In 2006, Trost and co-workers reported a one-pot synthesis of enantiopure N- and O-heterocyclic compounds using the combination of an achiral ruthenium catalyst and a chiral palladium complex. After the completion of the ruthenium-catalysed alkene-alkyne cross-coupling reaction between the... 

C-H bonds for C-C cross-couplings and annulation reactions. These ruthenium (II) catalysed cross-coupling reactions from C-H bonds have been recently presented in reviews [47, 48, 58]. Consequently, after a short presentation of the original examples this chapter will describe recent ruthenium(II) catalysed functionalization of sp C-H bonds and C-C bond formations, including the examples reported till the end of 2013, and discuss some catalytic mechanism aspects. 

The previous catalysts were adapted for the ruthenium-catalysed benzimidazoi-soquinoline synthesis via oxidative coupling of 2-arylbenzimidazoles with alkynes. Thus [RuCl2(p-cymene)]2, with 0.5-2 equiv. of Cu(0Ac)2.H20 in toluene at reflux produced a variety of benzimidazoisoquinolines. Unsymmetrical alkynes such as phenylpropionate led to the regioselective insertion with (Ph)C-C bond formation [(Eq. 91)] [180]. As an attempt to recover the catalyst, reactions were performed in PEG-400 as a solvent medium and the products were obtained in similar yields as in toluene and the catalyst could be recycled a few times [(Eq. 91)]. 

As another instance of a ruthenium-catalysed process, a macrocyclic taxoid, SB-T-2054 (134), was prepared from an unexpected diene-coupling reaction... 

Negishi E, Tan Z (2005) Diastereoselective, Enantioselective, and Regioselective Carbo-alumination Reactions Catalyzed by Zirconocene Derivatives. 8 139-176 Netherton M, Fu GC (2005)Pa]ladium-catalyzed Cross-Coupling Reactions of Unactivated Alkyl Electrophiles with Organometallic Compounds. 14 85-108 Nicolaou KC, King NP, He Y (1998) Ring-Closing Metathesis in the Synthesis of EpothUones and Polyether Natmal Products. 1 73-104 Nishiyama H (2004) Cyclopropanation with Ruthenium Catalysts. 11 81-92 Noels A, Demonceau A, Delaude L (2004) Ruthenium Promoted Catalysed Radical Processes toward Fine Chemistry. 11 155-171... 

Diels-Alder type [4 -1- 2] cycloadditions of nonactivated coupling partners have been effected by various transition-metal catalyses [1]. Interestingly, the cationic ruthenium complex 68 catalyzed the intramolecular [4 -1- 2] cycloaddition between alkyne and enone moieties of 97 leading to 98 (Scheme 4.38) [83]. Such a formal hetero Diels-Alder reaction might proceed via a mthenacyclopentene 99 and an oxam-thenacycloheptadiene 100, which is an mthenium enolate species. 

More recently, chemists seem to be able to invent multi-component reactions almost at will. An outstanding example is this four-component coupling catalysed by ruthenium. Three component, surely, do we hear you say The fourth component is the bromide ion.33... 

Scheme 3.10 Tandem alkene-alkyne cross-coupling reaction-intramolecular het-erocyclisation reaction catalysed hy a combination of ruthenium catalysis and chiral palladium catalysis.

Abstract The selective catalytic activation/functionalization of sp C-H bonds is expected to improve synthesis methods by better step number and atom economy. This chapter describes the recent achievements of ruthenium(II) catalysed transformations of sp C-H bonds for cross-coupled C-C bond formation. First arylation and heteroarylation with aromatic halides of a variety of (hetero)arenes, that are directed at ortho position by heterocycle or imine groups, are presented. The role of carboxylate partners is shown for Ru(II) catalysts that are able to operate profitably in water and to selectively produce diarylated or monoarylated products. The alkylation of (hetero)arenes with primary and secondary alkylhalides, and by hydroarylation of alkene C=C bonds is presented. The recent access to functional alkenes via oxidative dehydrogenative functionalization of C-H bonds with alkenes first, and then with alkynes, is shown to be catalysed by a Ru(ll) species associated with a silver salt in the presence of an oxidant such as Cu(OAc)2. Finally the catalytic oxidative annulations with alkynes to rapidly form a variety of heterocycles are described by initial activation of C-H followed by that of N-H or O-H bonds and by formation of a second C-C bond on reaction with C=0, C=N, and sp C-H bonds. Most catalytic cycles leading from C-H to C-C bond are discussed. 

The C-C bond cross-coupling reaction of sp C-H bond with alkylhalides following the ruthenium(II) catalysed C-H bond activation process has not been well explored in comparison with arylations with arylhalides, especially for the secondary alkylhalides which are more sterically demanding and electron-rich thus leading to the oxidative addition step with difficulty [106]. 

A ruthenium(II)-catalysed oxidative cross-coupling of phenylpyridine substrates with cycloalkanes has been reported (Scheme 31) [22]. The proposed mechanism involves directed metalation of phenylpyridine and formation of a ruthenium alkyl species in the presence of ferf-butyl peroxide as an oxidizing reagent. The reaction required an excess of oxidizing reagent (4 equiv. with respect to phenylpyridine) as... 

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