Selenol esters aromatic

Friedel-Crafts acylation.1 The complex (CuOTf)2C6H (5, 151-152) induces acylation of aromatics by selenol esters. Other copper salts (Cu20, CuCI2) are... 

In 1962 Renson et al. reported that a variety of selenol esters can be synthesized by the reaction of the appropriate acyl chlorides with selenols in the presence of pyridine. - Selenols can easily be prepared from elemental selenium and the corresponding Grignard reagents. In addition to simple selenol esters, a,P-unsaturated selenol esters (4) and (5) and o-substituted aromatic selenol esters (6) have been obtained by this method, as shown in Scheme 1. Butyl selenol esters are generally colorless or light yellow liquids, whereas the phenyl or substituted phenyl selenol esters are white solids, which are easily purified by recrystallization. More recently other groups have used Renson s method to synthesize similar selenol esters. " ... 

Areneselenyl magnesium bromide has been reported to react with /7-substituted benzoyl halides, giving aromatic selenol esters " as the first examples exhibiting liquid crystal properties (equation 2). ... 

Diaryl diselenides reacted with carbon monoxide (5-100 atm) at 100-200 °C, in the presence of Co2(CO)s as a catalyst, to give the corresponding selenol esters of aromatic carboxylic acids in 21-96% yields (equation 14)P... 

Moreover, the selenol esters can acylate reactive arenes and heteroaromatic compounds when cop-per(I) triflate is employed as the selenophilic metal cation. - The acylation of aromatics by use of the benzene complex of copper(I) triflate (43 Scheme 12) was complete within an hour at room temperature, with benzene as solvent, and the acylation products were obtained in high yields. Intramolecular acylation was examined successfully, as shown in equation (20). 

It was reported that UV irradiation of o-substituted aromatic selenol esters (54) led to the S//-[l]ben-zoselenino[2,3-b]pyridine (55) ring system via a selenol ester-seleninone transformation. ... 

Abe and co-workers revealed that the photochemical [2+2] cycloaddition (Pa-terno-Biichi reaction) of silyl enol ethers 86 of selenol esters to aromatic aldehydes affords the 3-selanyl-3-siloxyoxetanes 87 (trans cis=65 35-85 15) regio-selectively in good to high yields (Eq. 57) [110]. 

Macrolactonization has been accomplished using Thiol and selenol esters can also be prepared in one pot from carboxylic acids using (1) reaction of the intermediate (2) with aromatic thiols or selenols is complete within a few minutes in DMF, while aliphatic thiols require a few hours. Formation of the phenylthiol ester of IV-Cbz-L-phenylalanine was accompanied by only slight racemization. N,N -Carbonyldi-sym-triazine can be used in place of (1), with similar results. 

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. 

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