Green Aerobic Oxidation of Thiols to Disulfides by Flavin–Iodine Coupled Organocatalysis
作者:Hiroki Iida、Marina Oka、Ryo Kozako
DOI:10.1055/a-1520-9916
日期:2021.7
molecular iodine successfully promoted the aerobicoxidation of thiols to disulfides under metal-free mild conditions. The activation of molecular oxygen occurred smoothly at room temperature through the transfer of electrons from the iodine catalyst to the biomimetic flavin catalyst, forming the basis for a green oxidative synthesis of disulfides from thiols.
Primary alcohols are converted into dialkyl disulfides via heating in situ generated O-alkyl S-difluoro(ethoxycarbonyl)methyl xanthates from ethyl bromodifluoroacetate and potassium xanthates, prepared from primary alcohols and carbon disulfide in the presence of KOH. The reaction mechanism is suggested as an alkyl C[1,3] shift followed by a radical mechanism. This extends to the Chugaev elimination
Free-Radical Addition of Heteroarenethiols and Heteroarylmethanethiols to Hexyne and Phenylacetylene. Chemical Behavior of the Transient .beta.-Sulfanylvinyl Radicals
作者:Luisa Benati、Laura Capella、Pier Carlo Montevecchi、Piero Spagnolo
DOI:10.1021/jo00129a039
日期:1995.12
The free-radical reaction of a number of heteroarenethiols (including 2-thiophene-, 2-benzo[b]furan-and 2-benzo[b]thiophenethiol) and heteroarylmethanethiols (including 2-furyl-, 2-thienyl-, and 3-thienylmethanethiol) with hex-1-yne and phenylacetylene has been investigated in benzene solution both at 100 degrees C in the presence of AIBN and at room temperature in the presence of BEt(3)/O-2. Under both of these conditions the above thiols generally furnished transient 2-sulfanylvinyl radicals through regioselective addition of corresponding sulfanyl radicals to the terminal alkyne carbon, but 2-benzo[b]furanthiol failed to react with either alkyne in the presence of BEt(3)/O-2 and unexpectedely gave 2-(ethylsulfanyl)benzo[b]furan to a significant extent. The produced 2-(2-heteroarylsulfanyl) vinyl radicals largely preferred to undergo intermolecular H-abstraction reaction rather than intramolecular 5-endo cyclization onto the heteroaryl moiety of the 2-sulfanyl substituent. The 2-[(2-thienylmethyl)sulfanyl]- and, especially, 2-[(2-furylmethyl)sulfanyl]vinyl radicals, besides H-abstraction, promptly underwent intramolecular B-exo cyclization to give spiro radicals that interestingly underwent beta-scission of their respective C-S and C-O bond resulting in ring cleavage of the original heteroaryl group. The 2-[(3-thienylmethyl)sulfanyl]vinyl radicals did not exhibit any similar B-exo cyclization, but did undergo a 6-endo cyclization to a very slight extent.
Generation of Thiols by Biotransformation of Cysteine−Aldehyde Conjugates with Baker's Yeast
作者:Tuong Huynh-Ba、Walter Matthey-Doret、Laurent B. Fay、Rachid Bel Rhlid
DOI:10.1021/jf026198j
日期:2003.6.1
Baker's yeast was shown to catalyze the transformation of cysteine-furfural conjugate into 2-furfurylthiol. The biotransformation's yield and kinetics were influenced by the reaction parameters such as pH, incubation mode (aerobic and anaerobic), and substrate concentration. 2-Furfurylthiol wets obtained in an optimal 37% yield when cysteine-furfural conjugate at a 20 mM concentration wets anaerobically incubated with whole cell baker's yeast at pH 8.0 and 30 degreesC. Similarly to 2-furfurylthiol, 5-methyl-2-furfurylthiol (11%), benzylthiol (8%), 2-thiophenemethanethiol (22%), 3-methyl-2-thiophenemethanethiol (3%), and 2-pyrrolemethanethiol (6%) were obtained from the corresponding cysteine-aldehyde conjugates by incubation with baker's yeast. This work indicates the versatile bioconversion capacity of baker's yeast for the generation of thiols from cysteine-alclehyde conjugates. Thanks to its food-grade character, baker's yeast provides a biochemical tool to produce thiols, which can be used as flavorings in foods and beverages.
Pseudo Five-Component Synthesis of 3-(Hetero)arylmethyl-2,5-di(hetero)-aryl-Substituted Thiophenes via Sonogashira–Glaser Cyclization Sequence
The Sonogashira-Glaser sequence combined with a microwave-assisted cyclization is a powerful tool to synthesize unsymmetrically substituted conjugated thiophenes. A variety of 3-(hetero)arylmethyl-2,5-di(hetero)aryl-substituted thiophenes could be synthesized in moderate to excellent yields using a single Pd/Cu catalyst system. The presented method is strikingly simple to perform using commercially available starting materials. The obtained trisubstituted oligothiophene derivatives are interesting molecules for materials science.