Diphenyl ether analog synthesis

Pentafluorophenylcopper is representative of a series of fluori-nated organocopper compounds that are highly soluble in organic solvents, more thermally stable than their hydrocarbon analogs, and useful as synthetic intermediates. " Pentafluorophenylcopper has been used to introduce the pentafluorophenyl groups and as a reagent for an improved Ullman diphenyl ether synthesis. It is... 

In order to circumvent the problem of low yields in the usual Ullmann reaction, most syntheses of bisbenzylisoquinoline alkaloids have formed the diphenyl ether linkages at an early stage and confronted the problem of isomer separation later. In the case of phaeantharine (18) (Section II,A,3), which has no asymmetric carbons, this approach was clearly preferred. This synthesis exemplifies the use of Reissert alkylation as a key step (9,269). Several analogs of bisbenzylisoquinoline alkaloids were prepared in an analogous manner (270,271). One... 

The base or nucleophile in the Dow phenol process is aqueous NaOH that needs to be heated to 300° C, which is only possible at a pressure of 200 bar. This conconction is only just capable of deprotonating chlorobenzene to benzyne or of adding to the latter subsequently. Thus, there is no analogous synthesis of diaryl ethers from sodium phenolates and haloben-zenes. And as expected, the product resulting from the Dow process did not contain more than 15% of diphenyl ether. 

Our first synthetic analog (3) contains the three amide bonds involved in H-bonding to the carboxylate terminus as well as the key diphenyl ether functionality. The synthesis of (3) shown in scheme 1, involves a multistep sequence from 3-cyanophenol and D-(or L-) dinitrotyrosine. The nmr of (3) shows the 2-H proton resonance of the benzylamine ring to be shifted upfield... 

Freund and Wolf10 reported that 2,4-diphenyl-l,2,4-thiadiazolidine-3,5-dithione was formed by heating l,3-diphenyl-2-thiourea with thiophosgene in benzene whereas, a 1,3-thiazetidine was produced at lower temperatures in ether (see Section II). Ohande181 has reported that 3,5-diamino-l,2,4-thiadiazoles are formed by the reaction of thiopseudoureas with carbon disulfide in the presence of bromine. Use has also been made of thioureas in the synthesis of 1,3,4-thiadiazolines (79) via reaction with the halohydrazones 78.185,186 The analogous reaction with solenoureas was recently reported by Bulka and Ehlers187 to yield 1,3,4-selenadiazolines. 

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