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Nucleophilic hydroarylation

Product predictions for nucleophilic additions to C q, based on AMI calculations, show that among the many possible isomers a few are energetically favored [29]. Two areas within the molecule can be distinguished, which are the inert belt at the equator and the more reactive CgQ-like double bonds at the poles (Figure 3.4). Experimentally, hydroalkylation and hydroarylation reactions of C q under quantitative HPLC control yield predominantly one isomer of each C7oHR[4]. [Pg.80]

No racemisation is observed during the Pt(IV)-catalysed cyclisation of chiral propargyl ethers to chromenes. The PtCU catalyst appears to activate selectively the triple bond to nucleophilic attack by the arene and enables this well-established route to chromenes to be carried out under mild, neutral conditions and with a variety of substrates (Scheme 12) <03T8859>. A Pt-catalysed 6-endo hydroarylation of an alkynone combined with an intramolecular Michael addition are the key steps in a synthesis of the rotenoid deguelin <030L4053>. [Pg.411]

Murakami and coworkers reported a further use for this rhodium migration [80, 81]. Instead of protonolysis, they noticed that the aryl rhodium species after the vinylic to aryl migration is nucleophilic enough to attack an ester moiety in an intramolecular fashion to afford a cyclic ketone. Thus, an internal alkyne equipped with ester groups at a specific place was subjected to the rhodium-catalyzed hydroarylation conditions (Scheme 21). Indeed, the desired ketone was obtained in an 89% yield. Not only methyl esters can serve as acylation agents ethyl esters and isopropyl esters are also suitable substrates. [Pg.162]

Hydroarylation can also be mediated by Au(I) and Au(III) (Scheme 33) (384). In the case of aryl substituted alkynes, the Au(III) Ji complex undergoes electrophilic aromatic substitution with the electron-rich arene to give aLkenyl-Au(III) complex, which is immediately protonated by the H generated upon C C bond formation. For the Au(I)-catalyzed hydroarylation, the cationic gold complex k coordinates the alkyne, with subsequent nucleophilic attack by the arene from the opposite face leading to an alkenyl-gold complex, which is protonated to the desired products. The nature of the reaction causes the regioselectivity of this reaction to be sensitive to electronic rather than steric factors. [Pg.403]

The addition of sulfur nucleophiles to alkynes is a less developed transformation. However, Yamamoto described the attack of the sulfur atom of aryl thioethers to afford benzothiophenes (equation 31). More recently, it has been showed that propargylic thioethers or thioacetals undergo migration to give carbenes that cyclize in hydroarylation processes and thiocarbamates that evolve by propargylic rearrangement. Thiosilanes can perform as both sulfur nucleophiles and silicon electrophiles in intramolecular reactions to afford benzothiophenes (equation 32). ... [Pg.6582]

C.i.a. Sequential Hydroarylation (Hydroalkenylation)/Cyclization. Since the cis stereochemistry of addition pushes the substituents of the acetylenic moiety to the same side of the olefinic double bond, a cyclization reaction can follow the addition step when these substituents bear suitable nucleophilic and electrophilic centers, and the whole process resembles a valuable straightforward methodology for the preparation of cyclic compounds (Scheme 20). Cyclization can occur under hydroarylation(hydroalkenylation) conditions—either before or after the substitution of the carbon-hydrogen bond for the carbon-palladium bond—or by subjecting the isolated hydroarylation(hydroalkenylation) product to suitable reaction conditions. This strategy has been employed successfully to develop new routes to various heterocycles. [Pg.1345]

Electron-rich phenyl rings are also suitable nucleophiles for the intramolecular gold-catalyzed hydroarylation of allenes. Thus, dihydroquinoline and chromene derivatives are accessible by treating allenic anilines or allenic aiylethers with a cationic gold catalyst (Scheme 4-14). Because of the limited stability of... [Pg.443]

Intermolecular hydroarylations of terminal allenes with highly nucleophilic methoxyarenes are catalyzed by cationic phosphite gold(l) complexes. The addition takes place regioselectively at the unsubstituted allene terminus and affords ( )-allylated benzene derivatives with moderate-to-high yields. [Pg.444]

First gold-catalyzed reaction of aiienes, ketones as nucleophiles and step-wise two-fold hydroarylation... [Pg.146]

Even though less studied than the O- and A-nucleophiles, other important H-X bonds can participate in hydrofunctionalization catalyzed by gold. Hence, the intermolecular hydroarylation i.e. bond addition) of allenes... [Pg.333]

A highly electrophilic phosphite gold(I) catalyst was applied to the intramolecular allene hydroarylation reaction to give a vinyl-substituted carbocycle [17], This cyclization proceeds effectively in cases where the aryl groups are electron-rich arene nucleophiles. A dimethoxybenzene bearing an allene group furnished a vinyl-substituted tetralin derivative in 85% yield (Scheme 18.18). From the mechanistic... [Pg.464]

The reaction has been carried out with differently substituted alkynol derivatives and oxygen-, nitrogen-, and carbon-centered nucleophiles and applied to the synthesis of enantiomerically pure [3.3.1]bicyclic systems from the chiral pool. The mechanism parallels the one proposed for the hydroalkoxylation/hydroarylation sequence. [Pg.280]


See other pages where Nucleophilic hydroarylation is mentioned: [Pg.435]    [Pg.485]    [Pg.159]    [Pg.570]    [Pg.6583]    [Pg.1342]    [Pg.225]    [Pg.486]    [Pg.488]    [Pg.435]    [Pg.438]    [Pg.439]    [Pg.442]    [Pg.442]    [Pg.372]    [Pg.473]    [Pg.1342]    [Pg.146]    [Pg.149]    [Pg.88]    [Pg.255]    [Pg.387]    [Pg.334]   
See also in sourсe #XX -- [ Pg.73 ]




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Hydroarylation

Hydroarylations

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