Fluorinated Analogs of Organosulfur Compounds from Garlic (): Synthesis and Chemistry.

We report the first syntheses-from commercially available 3-chloro-2-fluoroprop-1-ene ()-of key garlic-derived compounds containing sp-fluorine. We also report synthesis of fluoro-5,6-dihydrothiopyrans by trapping 2-fluorothioacrolein (). Thus, difluoroallicin (, -(2-fluoro-2-propenyl) 2-fluoroprop-2-ene-1-sulfinothioate) is prepared by peracid oxidation of 1,2-bis(2-fluoro-2-propenyl)disulfane (). -2-Fluoro-2-propenyl-l-cysteine (2-fluorodeoxyalliin, ), synthesized from cysteine and characterized by X-ray crystallography, is oxidized to its -oxide, 2-fluoroalliin (). The latter, with alliinase-containing powdered fresh garlic, gives a mixture of , allicin (), and isomers of monofluoroallicin (), indicating that serves as a substrate for garlic alliinase. Upon heating, generates transient , which dimerizes giving difluoro vinyl dithiins and . Ethyl acrylate trapping of affords 5- and 6-substituted 3-fluoro-5,6-dihydro-4-thiopyrans ( and ). In 1,1,1,3,3,3-hexafluoro-2-propanol (HEFP) as solvent, is converted into trifluoroajoene ((,)-1-(2-fluoro-3-((2-fluoro-2-propenyl)sulfinyl)prop-1-en-1-yl)-2-(2-fluoro-2-propenyl)disulfane; ). Liquid sulfur converts to a (CH=CFCH)S mixture (n = 4-15), characterized by UPLC-(Ag)-coordination ion spray-mass spectrometry.