Crystalline diazonium trifluoroacetate salts
Pd-catalyzed C-C coupling
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
-We have developed a very mild procedure for the synthesis of crystalline aryldiazonium trifluoroacetate salts in high yields under anhydrous conditions. Over thirty mono- or polyfunctional aniline derivatives have been diazotized by this method, including water- and acid-sensitive substrates. The o- and p-hydroxyaryldiazonium salts, derived from the corresponding anilines, could be deprotonated by treatment with K2CO3 to yield pure diazoquinones. NMR and UV/Vis spectra have been recorded for all the synthesized salts; the data are in good agreement with the rather limited published data and constitute a first extensive report of 13C-NMR chemical shifts in diazonium salts. An excellent linear relationship emerged between Brown's substituent constants s+p and the 13Cipso chemical shifts. The diazonium salts obtained proved to be much more soluble in organic solvents than their tetrafluoroborate counterparts. They were tested in Pd-mediated coupling reactions of various Carbon-Carbon double bonds, and were found to give good yields within short reaction times under very mild conditions. We believe that diazonium trifluoroacetates represent a very attractive alternative to diazonium tetrafluoroborates.
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