Electrochemical Fluorination of Anthracene Derivatives. II

Abstract

The controlled potential electrolyses of anthracene(I), 9-methylanthracene(II), and 9-phenylanthracene(III) in acetonitrile solutions containing (CH3h NF.2HF led to the formation of fluoro derivatives in the 9-and 10-positions. Yields were limited by dimer formation. The products from the electrolyses areconsistent with the involvement of radical cations as intermediates.

Syntheses of 9,10-disubstituted anthracenes derived from 9,10-dilithioanthracene

“…9-fluoro-10-bromoanthracene, available by bromination of 9-fluoroanthracene, with Mg affords the Grignard reagent; reaction with perchloryl fluoride gives the difluoride in an unspecified yield percent.16 A seven-step route from octahydroanthracene also provides the difluoride.17 Finally, electrolysis of anthracene in an acetonitrile solution of (CH3)4NF-2HF gives 9,10-difluoroanthracene in 0.1% yield. 18 We find that reaction of 9,10-dilithioanthracene with 7V~tert-butyl-jV-fluorobenzenesulfonamide19'20 yields difluoride 2d in one step in 60% yield after column chromatography. Attempted reaction with N-fluoro-2,4,6-trimethylpyridinium triflate21 led only to proton abstraction and anthracene formation; in fact, the literature suggests that lithium salts are not good starting materials for fluorinations with the N-fluoropyridinium inflates.21® Attempted reaction of 9,10-dilithioanthracene with XeF2 (-78 -» +23 °C) afforded a complex mixture of products, one of which as the desired difluoride (2d) as confirmed by mass spectrometry and TLC comparison with an authentic sample.…”