Alkenylation of arenes

Friedel-Crafts alkenylation of arenes with various phenylacetylenes to yield 1,1-diarylalkenes was reported. Alkyl-substituted benzenes and naphthalene react with phenylacetylene in the presence of zeolite HSZ-360 to afford the products in good to excellent yields and selectivities 415... 

The C-H/olefin coupling of aryloxazolines proceeds with unusual product selectivity. In this case, alkylation products, i.e., formally dehydrogenation products, are obtained as a major product (Eq. 22) [11]. These types of dehydrogenation compounds are believed to be formed via a carbometalation pathway. The first example of this type of alkenylation of arenes with olefins using palladium(II) complexes via C-H bond cleavage was reported in 1967 [32]. Later, several efforts were made to perform this reaction in a catalytic manner [33]. In 2001, Milstein et al. [34] reported the oxidative alkenylation of arenes with olefins using a Ru/02/C0 catalyst system (Eq. 23). Details of the reaction mechanism have not been elucidated. 

Numerous transition and rare earth metal triflates were screened as catalysts for the alkenylation of arenes with alkynes, a transformation that can be performed only with difficulty in conventional solvents, see Scheme 9.23. Particularly with electron deficient alkynes such as p-trifluormethylphenylacetylene and />-chlorophenylacetylene the presence of an ionic liquid was found to be mandatory to observe any catalysis. Highest activity was obtained with Hf(OTf)3, In(OTf)3 and Sc(OTf)3 and the reaction proceeded smoothly, even at relatively low catalyst loadings. It is proposed... 

The gold-catalyzed intermolecular hydroarylation of alkynes (or alkenylation of arenes) leads to 1,1-disubstituted alkenes (equation 91) 240-243 1 2-Disubstituted derivatives are obtained from alkynes with electron-withdrawing groups (equation 92). ... 

In 2001, Mdstern reported on the oxidative alkenylation of arenes with olefins using a RU/O2/CO catalyst system (Eq. 9.12) [26], but details of the reaction mechanism have not been elucidated. Very recently, Gunnoe reported ethylation and propylation of ben-... 

Innovative catal)rtic protocols for the ring-closing Friedel-Crafts-type alkylation and alkenylation of arenes and hetarenes 06EJO3527. 

Choi, D. S., Kim, J. H., Shin, U. S., Deshmukh, R R, and Song, C. E. (2007). Thermodynamically- and kinetically-controlled Frledel-Crafts alkenylation of arenes with allq nes using an acidic fluoroanti-monate (V) ionic iiquid as catalyst. Chem Commun, pp. 3482-3484. 

Ruthenium-catalyzed direct oxidative alkenylation of arenes through twofold C—H bond functionalization 13CS886. 

Yu and coworkers [14] reported that the alkenylation of arenes possessing electron-withdrawing group(s) under Pd catalysis occurs at their meta position preferentially (Scheme 18.14). 

The direct catalytic alkylation of C(sp )-H bonds with alkenes to create C-C bonds offers an atom-economical alternative to other C-H alkylation methods, as it does not require a sacrificial functional group. In a seminal report, Yamazaki and coworkers [72] described that a dehydrogenative alkenylation of arenes with alkenes yielded a regioisomeric mixture of alkenylation and alkylation products in the presence of Rh4(CO)i2 (Scheme 19.46). 

Scheme 19.46 Dehydrogenative alkenylation of arenes with alkenes using Rh4(CO),2.

SCHEME 24.32 Representative examples for aerobic alkenylation of arenes. 

Duan and coworkers recently reported the use of a bidentate hgand for Pd-catalyzed alkenylation of arenes using Cu(OAc)j as the stoichiometric oxidant (Scheme 24.37) [34]. Specifically, the Pd(OAc)2/46 catalyst system is effective for the coupling of arenes with mono- and disubstituted alkenes. A variety of electronically differentiated monosubstituted arenes couple with -butyl acrylate to afford the products in good to excellent yields. In analogy to the aforementioned alkenylations, theoKta-substituted alkenes are... 

The use of ionic liquids as solvents dramatically increased the catalytic activity of Sc(OTf)3, and it exhibited unusually high activity for Friedel-Crafts alkylation of aromatic compounds with linear or cyclic olefins in imidazolium-based hydrophobic ionic liquids such as [EMIm]SbF6, [BMIm]PF6, and [HMIm]PF6. It should be noted that no reaction occurred in common organic solvents, water and hydrophilic ionic liquids [45]. This kind of activity enhancement of Sc (OTf) 3 by means of ionic liquid solvents was also observed in the Friedel-Crafts alkenylation of arenes with alkynes [46]. 

A review of the arylation and alkenylation of arenes includes studies of the pheny-lation of benzoic acid derivatives. " There has been an investigation of the reactions of methylquinolines with tritium-labelled nucleogenic phenyl cations, which may result in electrophilic substitution or in the formation of A-phenylquinolinium derivatives. ... 

As part of our investigation of the hydroarylation of alkynes (or alkenylation of arenes) catalyzed by electrophilic transition metal complexes, our group reported the intra- and intermolecular reaction of indoles with alkynes catalyzed by gold (see Ref. [118, 133] in Chap. 1). Thus, alkynyUndole III-l cycUzes readily in the presence of a cationic gold(I) complex to give azepino[4,5-h]indole derivative III-2, whereas the use of AuCls leads to indoloazocine III-3 by a S-endo-dig process, this cyclization mode has not been observed in other hydroarylation of alkynes (Scheme 4.7). Under certain forcing conditions, aUenes and tetracyclic compounds were also obtained (see Refs. [118, 133] in Chap. 1). 

Friedelr-Crafts Alkenylation. Hf(OTf)4 jointly used with an ionic liquid catalyzed the Friedel-Crafts alkenylation of arenes. Moreover, the ionic liquid phase containing catalyst could he readily recovered by simple decantation of the organic layer after reaction and reused for the following runs without any significant loss of activity (eqs 19 and 20). ... 

These examples demonstrate that a ruthenium(ll) catalyst precursor can lead to alkenylation of arenes at ortho position of ketone and amide functions without oxidant beside an acid. Whereas ketones did not allow the arylation at their ortho... 

A New Method of Alkenylation of Arenes with Ruthenium (II) and Copper(II)... 

Scheme 16 Proposed mechanism for directed ort/to-alkenylation of arenes and heterocycles...

Since 2011, the ruthenium(ll) catalysed alkenylation of arenes, alkenes, heterocycles, ferrocenes has been established as a catalytic method to produce a large variety of functional alkenes. The reaction requires a Ru(ll) catalyst associated with an oxidant such as Cu(0Ac)2.H20. More importantly using usually [RuCl2(arene)]2 catalyst with a slight excess of silver salt in the presence of an oxidant Cu(OAc)2 under air the alkenylation of (hetero)arenes and alkenes can be directed by weakly coordinating groups such as ketone, aldehydes, amides, carbamates, and esters. 

A simple and practical Cu(OTf)2-catalyzed synthesis of quinoline-2-carboxylates through tandem Grignard-type imine addition/Friedel-Crafts alkenylation of arenes with aryl or alkyl alkynes via activation of C-H bonds was reported in 2009 (Scheme 8.84). The quinoline-2-carboxylates products could be obtained in high yields from a number of readily available alkynes and imines at room temperature [154]. 

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