Mercapto fluoride

Dann and Dimmling showed that (2,5-dimethyl-3-thienylthio)acetic acid (86) may by cyclized to 4,6-dimethyl-2,3-dihydrothieno[3,4-6]-thiophen-3-one (87) by anhydrous hydrogen fluoride, and then reduced to 4,6-dimethylthieno[3,4-b]thiophene (88). The latter was obtained by cyclization of acetal (89) synthesized from 3-mercapto-2,S-c ethylthiophene (90) and bromoacetaldehyde dimethylacetd using hydrogen fluoride at 70°-80°. The synthetic route is illustrated by Scheme 6. 

Substituted-6-methyltriazolo[3,4-/ ][l,3,5]thiadiazines 229 are obtained in 18-88% yield by the bis-Mannich reaction of 3-substituted-5-mercapto-l,2,4-triazoles 226 and formaldehyde in the presence of acid (Scheme 42) <1999SC2027, 2001SC2841>. It has been found that the pH of the reaction mixture plays an important role and the optimum pH is in the range 5-6. Addition of a catalytic amount of potassium fluoride to the reaction further enhanced the overall yield <2001JHC929>. Chiral 1,3,5-thiadiazines are obtained when a chiral amine such as S(—)-a-phenylethylamine is used. 

Other complexing agents used to eliminate or reduce the influences of metal ions on the determination of hydride forming elements are cyanides, thiocyanates, tartaric acid, citric acid, ammonium fluoride, and 2-mercapto-propionic acid. 

SCHEME 8.7 Schematic illustration of the process of ozone prelrealment, graft copolymerization PVDF with PMA, preparation of PVDF-g-PPMA membrane with clickable surface by phase inversion, preparation of functional PVDF-g-P[PMA-cZ/ck-MPS] membranes via surface thiol-yne click reaction of thiols on the PVDF-g-PPMA membrane, and preparation of PVDF-g-P[PMA-c//ck-P-CD] membranes via surface alkyne-azide click reaction on the PVDF-g-PPMA membranes. PVDF, poly(vinylidene fluoride) PMA, propargyl methacrylate MPS, 3-mercapto-l-propanesulfonic acid sodium salt azido-fl-CD, mono(6-azido-6-desoxy)-P-cyclodexIrin. Reprinted with permission from Reference 168. Copyright 2011 American Chemical Society. 

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