Triflate with phenols

Several reports have been made of a successful catalyzed addition/ substitution reaction resulting in direct attachment of phosphorus to aromatic rings. The preparation of mixed triarylphosphines has been accomplished by the reaction of tin- or silicon-substituted diphe-nylphosphines with aryl halides catalyzed by palladium reagents.74 A similar transformation has also been reported using nickel catalysis.75 The addition/substitution of diphenylphosphine to triflate functionalized phenolic linkages has been of use for the preparation of substances as analogues of tyrosine-related amino acid derivatives, accomplished with catalysis by palladium acetate (Equation 4.29).76... 

There has been a summary of the use of insertion reactions of arynes into a-bonds to prepare nrt/io-disubs tituted arenes. A key to the success of these processes is the ability to generate benzyne under mild conditions by the reaction of readily available o-(trimethylsilyl)phenyl triflate with fluoride ions.61 Reaction of amines and their derivatives with benzynes generated in this way has been shown to be an efficient method for the production of N-arylated derivatives, as illustrated in Scheme 8. The method also works well in the O-arylation reactions of phenols and carboxylic acids 62... 

Most Williamson reactions proceed by the 8 2 mechanism, but there is evidence (see p. 446) that in some cases the SET mechanism can take place, especially with alkyl iodides. Secondary alcohols have been converted to the corresponding methyl ether by reaction with methanol in the presence of ferric nitrate nonahy-drate. Vinyl ethers have been formed by coupling tetravinyl tin with phenols, in the presence of cupric acetate and oxygen. " The palladium-catalyzed coupling of vinyl triflates and phenols has also been reported. ... 

Palladium-catalyzed carbonylation of aryl triflates in the presence of an alcohol141 or amine1423 provides a good method for preparation of arenecarboxylic esters and amides from phenols (equation 121). However, palladium-catalyzed cyanation of 5,6,7,8-tetrahydro-2-naphthyl triflate with potassium cyanide failed completely whereas the more reactive tetrakis(triphenylphosphine)nickel(0) could catalyze the same reaction which gives the nitrile in a good yield142b (equation 122). 

Thienyl(phenyl)iodonium salts and other heteroaryl(phenyl)iodonium salts can be used as the selective heteroaryl transfer agents in reactions with phenol ethers. These heteroarylations occur at room temperature in the hexafluoroisopropanol solution in the presence of trimethylsilyl triflate via a SET mechanism [876]. 

The mechanism involves the oxidative addition of the vinyl or aromatic triflate or halide to give an organopalladium intermediate. TransmetaUation with the organostannane forms another organopalladium intermediate with two Pd—C a bonds. A reductive elimination step releases the product and thereby regenerates the palladium(0) catalyst. Vinyl triflates can be made from enolizable aldehydes or ketones and aryl triflates from phenols, but the reaction also works with vinyl and aryl halides. 

As a related reaction, thiophenols are prepared from phenols. For example, the Pd-catalyzed reaction of 2-naphthyl triflate with sodium triisopropylsilane thiolate (56) gives the silyl ether of 2-thionaphthol 57. Deprotection of 57 affords 2-thionaphthol (58) [17]. 

Itami et al. observed that an aryl ester could replace an aryl halide in their azole arylation protocol such a finding led to the first method for Ar-H/Ar-0 couplings and dramatically increased its synthetic utility simply due to the availability of phenols. The Ni(cod)2/dcype catalyst system was active for the coupling of azoles 152 with phenol derivatives such as carbamates, carbonates, mesylates, triflates, and tosylates to afford 2-arylazole products 153A-D in high yields (Scheme 10.53). ... 

Aryne Annulation. Treatment of o-(trimethylsilyl)aryl triflates with TBAT results in the formation of ben-zyne intermediates. Fluoride-induced 1,2-eliminations of o-(trimethylsilyl)aryl triflates, which are readily prepared from phenols, have been shown to provide the respective aryne products, which, at room temperature, precipitously undergo cycloaddition in the presence of Diels-Alder adducts, including, but not limited to, tethered acyclic dienes, tethered enynes (eq 15), azomethine imines (eq 16),ene carbamates, and acetamidoacry-lates (eq 17). ... 

Aliphatic nitriles react slowly with phenols and phenyl ethers in the presence of trifluoromethanesulphonic acid to give ketones after hydrolysis, in a variation of the Houben-Hoesch reaction. The crystalline complex of copper(i) triflate and benzene induces the acylation of aromatic substrates with selenol esters, affording a transition-metal mediated version of the Friedel-Crafts reaction. Aromatic carboxylic acids can be converted into symmetrical diaryl ketones in good yield by treatment of their 5-(2-pyridyl)thioesters with bis-(l,5-cyclo-octadiene)nickel [equation (15)]. In contrast to other methods for preparing symmetrical aromatic ketones, this method allows their preparation from a single starting material. 

In none of our extensive test reactions of aryl halides with benzoic acids carried out in the presence of diverse palladium catalysts, we were able to detect even traces of the unsymmetrical biaryl. Instead, we observed mostly homocoupling and dehalogenation products in some cases along with phenol esters. The conversion of aryl triflates with potassium benzoates did not lead to the desired biaryls, either, but to the phenol esters instead. 

Zheng D, Wan Z, Wu J (2011) Silver triflate catalyzed reaction of 2-tilynylbenztildoxime with phenol a general and facile route to 1-aroxyisoquinolines. Synthesis 2810-2816... 

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