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Furan arene alkylation

Arenes and heteroarenes which are particularly easy to metalate are tricarbo-nyl( 76-arene)chromium complexes [380, 381], ferrocenes [13, 382, 383], thiophenes [157, 158, 181, 370, 384], furans [370, 385], and most azoles [386-389]. Meta-lated oxazoles, indoles, or furans can, however, be unstable and undergo ring-opening reactions [179, 181, 388]. Pyridines and other six-membered, nitrogen-containing heterocycles can also be lithiated [59, 370, 390-398] or magnesiated [399], but because nucleophilic organometallic compounds readily add to electron-deficient heteroarenes, dimerization can occur, and alkylations of such metalated heteroarenes often require careful optimization of the reaction conditions [368, 400, 401] (Schemes 5.42 and 5.69). [Pg.176]

Friedel-Crafts Alkylation Reactions. The activation of glyoxylate esters,trifluoromethyl pyruvate esters, and unsaturated a-ketoesters by catalyst 2 converts these materials into effective electrophiles for asymmetric Friedel-Crafts alkylation reactions with activated arenes (eqs 16 and 17). In fact, bis(triflate) (2) is far superior to tbe bis(hexafluoroantimonate) complex at catalyzing the enantioselective alkylation of benzene derivatives. Aniline and anisole derivatives both give the reaction, as do heterocyclic aromatic compounds such as indole and furan. [Pg.422]

Yet the reaction that attracted more interest has been the conjugate addition of arenes. It was first described by Hashmi in 2000 that enones and furans could react in the presence of AuCls. In the reported cases, furans were also formed by a gold-catalyzed reaction of allenones (equation 133). Electron-rich substituted benzenes also underwent 1,4-addition with Michael acceptors. Later, 7-azaindoles (equation 134) were shown to provide 3-alkylated derivatives. On the other hand, indoles (equation 135) reacted selectively... [Pg.6602]

So far only one example of furan alkylation assisted by arene complexes has been reported. D.J. Milner has shown that furan reacts with tert-hutyl chloride in the presence of (TX -mesitylene)Mo(CO)3 to afford a mixture of 2-fert-butyl-furan and 2,5-di-tert-butylfuran in 65-80% yields [20]. Both mono- and disub-stituted furans can be prepared as the major product by changing the furan/t-BuCl ratio. Although there is only one report of this reaction, the ability to synthesize mono- and disubstituted furans in a simple manner reflects the potential of this methodology which can be used for preparing substituted furans, that are valuable synthetic materials. [Pg.187]

Other parameters of the palladium(n)-catalysed benzofuran synthesis were explored. Ultimately, it was found that the ideal system employed a 2 1 ligand/palladium ratio (10mol% Pd(OAc)2 and 20mol% ethyl nicotinate) and a substoichiometric amount (20mol%) of NaOAc at 100 °C. With this system in hand, a variety of substituted benzo-furans were accessed (Figure 9.7). The reaction was limited to electron-rich aryl systems the palladation event required a sufficiently nucleophilic arene in order to occur. The aryl subunit, however, tolerated an array of alkyl and alkoxy substitution patterns within the... [Pg.372]

As noted in Chapters 2 and 11, a series of -q -arene complexes of osmium have been prepared, and the reactivity of these species has been studied extensively by Harman. The reactions of iq -arene complexes of Os(II) illustrate how strong backbonding can cause the uncoordinated portion of an aromatic system to be more susceptible to electrophilic attack than the corresponding free arene. ° Osmium(II) pentamine complexes of phenols, anilines, acetanilides, and anisoles react with electrophiles at the uncoordinated portion of the ring. For example, the simple phenol complex in Equation 12.78 reacts with Michael acceptors at the 4-position of the coordinated phenol in the presence of a mild tertiary amine base. This reactivity and selectivity for reaction at the 4-position is greater than the reactivity of free phenol. The reactions of electrophiles with aniline derivatives occur in a similar fashion and lead to products from alkylation of the aromatic ring predominantaly at the 4-position (Equation 12.79). Related reactions occur with complexes of electron-rich five-membered pyrrole and furan heterocycles. Examples of electrophilic attack on -q -pyrrole complexes of Os(II) are shown in Equation 12.80. ... [Pg.475]

Intramolecular palladium-catalyzed alkylations of (hetero)arenes have been pioneered by Wong and Song [25], who described in 1994 a direct benzylation of furans within a domino sequence starting with the intermolecular Suzuki- Miyaura coupling of furylboroxines with o-bis(bromomethyl)arenes (Scheme 19.14). Mixtures of the cross-coupled product and the corresponding homocoupled furan were almost always obtained. [Pg.1436]

The iron-catalyzed alkylation of hetero(arenes) has also been described by employing a similar metallation strategy (Scheme 19.34) [54]. Furan, thiophene, and pyridine proved to be successftd heteroaromatic partners with both primary and secondary alkyl halide electrophiles. Electron-deficient arenes were also efficiently alkylated, but less acidic substrates such as tetrafluoroanisole failed to provide the desired alkylated product... [Pg.1449]

Hydroarylation of alkenes offers a more atom-economical process of catalytic C-H bond alkylation. It involves the transition-metal catalysed formal addition of the arene C-H bond onto C=C bonds. Especially T. B. Gtiimoe and his group have shown that ruthenium(II) catalysts favour the addition of aromatic C-H bonds to an olefin C=C bond. They have used ruthenium(II) catalysts of type TpRu-R(L) (NCMe) (Tp=hydrotris(pyrazolyl)borate) and demonstrated the efficiency of the formation of ethylbenzene via catalytic addition of benzene to ethylene [(Eq. 37)] [113-118]. Analogously the same type of catalyst TpRu-R(L)(NCMe) promotes the alkylation by ethylene at C2 position of furan and thiophene [119]. [Pg.145]

Deprotonative alkylation of arene C-H bonds by alkyl iodides and bromides is achieved in the presence of catalytic amounts of iron(III) chloride, /ra s-A,Ar-dimethyl-cyclohexane-1,2-diamine, and 2,2,6,6-tetramethylpiperidin-l-ylmagnesium chloride lithium chloride complex (TMPMgCl LiCl) as a base. Furans, thiophenes, pyridines, and some electron-deficient arenes can be employed in this reaction (Scheme 4-241). ... [Pg.696]


See other pages where Furan arene alkylation is mentioned: [Pg.232]    [Pg.133]    [Pg.134]    [Pg.137]    [Pg.185]    [Pg.204]    [Pg.249]    [Pg.169]    [Pg.96]    [Pg.222]    [Pg.207]    [Pg.116]    [Pg.715]    [Pg.650]    [Pg.266]    [Pg.585]    [Pg.96]    [Pg.491]    [Pg.269]    [Pg.166]    [Pg.235]    [Pg.119]    [Pg.177]    [Pg.356]    [Pg.689]    [Pg.434]   


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Alkyl arenes

Alkyl furans

Alkylated Arenes

Arenes alkylation

Furans alkylation

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