Rapid 18 F- and 19 F-Difluoromethylation through Desulfurative Fluorination of Transient N-, O-, and C-Linked Dithioles.

The difluoromethyl group plays an important role in modern medicinal and agrochemistry. While several difluoromethylation reagents have been reported, these typically rely on difluoromethyl carbenes or anions, or target specific processes. Here, we describe a conceptually unique and general process for O-H, N-H and C-H difluoromethylation that involves the formation of a transient dithiole followed by facile desulfurative fluorination using silver(I) fluoride. We also introduce the 5,6-dimethoxy-1,3-benzodithiole (DMBDT) function, which undergoes sufficiently rapid desulfurative fluorination to additionally support 18 F-difluoromethylation. This new process is compatible with the wide range of functional groups typically encountered in medicinal chemistry campaigns, and the use of Ag18 F is demonstrated in the production of 18 F-labeled derivatives of testosterone, perphenazine, and melatonin, 58.0±2.2, 20.4±0.3 and 32.2±3.6 MBq µmol-1 , respectively. We expect that the DMBDT group and this 18 F/19 F-difluoromethylation process will inspire and support new efforts in medicinal chemistry, agrochemistry and radiotracer production.

trans-Trifluoromethyltetrafluorosulfanyl Chloride: Selective Synthesis and Reaction with Diazo Compounds.

trans-Trifluoromethyltetrafluorosulfanyl chloride (trans-CF3SF4Cl) is a unique reagent for the incorporation of the CF3SF4 group into organic compounds. However, CF3SF4Cl was prepared from hazardous reagents or formed as mixture of trans and cis isomers in low yield. Herein, a silver-promoted selective synthesis of trans-CF3SF4Cl under safe gas-reagent-free conditions is described. Furthermore, the synthetic application of trans-CF3SF4Cl is demonstrated through the new trifluoromethyltetrafluorosulfanylation of α-diazo carbonyl compounds.

Fluorodesulfurization of Thionobenzodioxoles with Silver(I) Fluoride.

Difluorobenzodioxole is an important functional group found in both pharmaceuticals and agrochemicals. The late-stage introduction of this functional group is challenged by typical fluorination conditions of HF and strong oxidants. Here, we demonstrate that a range of difluorobenzodioxoles can be prepared from catechols in two steps through conversion into thionobenzodioxoles, followed by desulfurative fluorination with silver(I) fluoride. These mild reaction conditions are compatible with a variety of functional groups and enable access to a range of functionalized difluorobenzodioxoles.

Quaternary Ammonium Trifluoromethoxide Salts as Stable Sources of Nucleophilic OCF3.

The reaction of nucleophilic tertiary amines with trifluoromethyl and pentafluoroethyl methyl ethers provides quaternary ammonium trifluoromethoxide (NR4OCF3) and pentafluoroethoxide (NR4OCF2CF3) salts, respectively, in good yields. The new trifluoromethoxide salts disclosed herein are uniquely stable for extended periods of time in both the solid state and in solution, which complements contemporary reagents. Here we describe the preparation of a range of NR4OCF3 salts, their long-term stability, and utility in substitution reactions.

Base-Catalyzed Transesterification of Thionoesters.

Here we report a convenient synthesis of thionoesters by base-catalyzed transesterification. Benzyl and alkyl thionobenzoates and thionoheterobenzoates were efficiently prepared using various alcohols catalyzed by the corresponding sodium alkoxide. This methodology features a broad substrate scope, good to excellent yields, short reaction times, while simultaneously driving the reaction toward completion through the removal of the methanol byproduct. We also report the conversion of a small collection of thionobenzoates into the corresponding α,α-difluorobenzyl ethers to demonstrate the conversion of alcohols into difluorobenzyl or difluoroheterobenzyl ethers, a process that could prove useful for lead optimization in medicinal chemistry.