Making use of a convenient synthetic approach to prepare the deuterated S-3-(hexan-1-ol)-cysteine by a Michael addition reaction, an analytical method was developed to measure the presence of the cysteine S-conjugate, precursor of 3-sulfanylhexan-1-ol (3-mercaptohexan-1-ol), in must and wine from Petite Arvine vine. The method uses a stable isotope dilution assay with a suitable one-step sample preparation and HPLC-MS detection. The method has limits of detection and quantification of 3 and 10 microg/L, respectively. A correlation between the increase of the precursor concentration and the increase of the degree of rot has been established.

Six different fluoroarenes were submitted to the same transformations. Direct deprotonation with alkyllithium or lithium dialkylamide as reagents and subsequent carboxylation afforded the acids 1, 6, 11, 16, 18, and 23. If the aryllithium intermediate was trapped with iodine rather than with dry ice, an iodofluoroarene (2, 7, 12, 17, 19, and 24) was formed. This, upon treatment with lithium diisopropylamide, underwent deprotonation and iodine migration. The resulting new A carbon-bound metal participating in a synthetic reaction sequence is equivalent to a joker in a card game, being replaceable by virtually anything. Under such circumstances, the principal skill required is to steer the metal to the targeted position. This task is trivial if this position happens to be the most acidic site, which can generally be efficaciously submitted to a hydrogen/metal permutation reaction with an alkyllithium or a lithium dialkylamide. However, depending on the substrate structure, it may prove quite challenging to attack any other position selectively. Among the strategies [1Ϫ2] developed to circumvent this obstacle, the basicity gradient-driven relocation of a heavy halogen and its subsequent replacement by a metal is a particularly attractive option. Its scope and limitations have been explored in the systematic investigation described below.When treated with sec-butyllithium in tetrahydrofuran (THF) at Ϫ75°C, 1,3-difluorobenzene was deprotonated exclusively at the doubly activated position flanked by the two halogens. [3] Carboxylation of the resulting organometallic intermediate produced 2,6-difluorobenzoic acid (1; 78%), [3] while iodolysis afforded 1,3-difluoro-2-iodobenzene (2; 98%). When the latter compound was exposed to lithium diisopropylamide (LIDA) in tetrahydrofuran, it underwent lithiation at a fluorine-adjacent site. The thus generated intermediate, however, could not be trapped as such. It in- [a]

[reactions: see text] 2,4-Difluoropyridine, 2,4-dichloropyridine, 2,4,6-trifluoropyridine, 2,4,6-trichloropyridine and 2,3,4,6-tetrafluoropyridine react with standard nucleophiles exclusively at the 4-position under halogen displacement. However, the regioselectivity can be completely reversed if a trialkylsilyl group is introduced in the 5-position of the 2,4-dihalopyridines or in the 3-position of the 2,4,6-trihalopyridines or 2,3,4,6-tetrahalopyridine. Then only the halogen most remote from the bulky silyl unit (at the 2-position in the case of the 2,4-halopyridines, at the 6-position with the other substrates) gets involved in the exchange process. After removal of the silyl protective group the nucleophile is invariably found to occupy the nitrogen-neighboring position.

Starting from six industrially available fluorinated pyridines, an expedient access to all three tetrafluoropyridines (2-4), all six trifluoropyridines (5-10), and the five non-commercial difluoropyridines (11-14 and 16) was developed. The methods employed for the selective removal of fluorine from polyfluoropyridines were the reduction by metals or complex hydrides and the site-selective replacement by hydrazine followed by dehydrogenation-dediazotation or dehydrochlorination-dediazotation. To introduce an extra fluorine atom, a suitable precursor was metalated and chlorinated before being subjected to a chlorine/fluorine displacement process.

A homologous series of biosurfactants has been synthesized by a novel sustainable biotransformation technique and compared with three other enzymatic processes. 6-O-Alkanoyl-methyl-a-D-glucopyranosides were obtained by lipase mediated esterification of methyl-a-D-glucopyranoside with capric acid C 10:0 , lauric acid C 12:0 , myristic acid C 14:0 , palmitic acid C 16:0 , and oleic acid C 18:1 . Solvent free transformations were compared with the use of ionic liquids and organic solvents. The lipase from Candida antarctica B, immobilized on macroporous acrylic acid beads (Novozyme 435), was employed either untreated or coated with small amounts of ionic liquids. This resulted in superior efficiencies (80%) with 1-butyl-4-methylpyridine hexafluorophosphate [4bmpy][PF 6 ] and broader substrate tolerance in comparison to solvent free transformation. The results show a positive correlation with increasing polarity of the ionic liquids used as liquid film-coating, which was in opposition to the use of the same ionic liquid as solvent. The analysis of the ionic liquid film coated catalyst carriers was performed by optical and scanning electron microscopy (SEM).