Sulfur trifluorides

When the 2-hydroxy group of a monosaccharide reacts with (diethylamino)sulfur trifluoride (DAST), quantitative and stereoselective rearrangements are observed (K.C Nico-laou, 1986). This reaction may simultaneously introduce fluorine to C-1 and a new oxygen, sulfur, or nitrogen residue to C-2 with inversion of configuration. 

The high cost of SF and the incomplete use of fluorine justify its use only for inaccessible ben2otrifluorides. The related Hquid S—F reagent, (diethylarnino)sulfur trifluoride (DAST), (C2H )2NSF2, also effects similar transformations with aromatic carboxyhc acids (108). 

Compounds bearing C(=S)-NH-C-C-OH fragment ((3-hydroxy thioamide) can also undergo cyclodehydration to form thiazoline derivatives. The utility of this strategy has been demonstrated in the synthesis of halipeptins A and D <06JA4460>. Exposure of 73a/b with (diethylamino)sulfur trifluoride (DAST) brings about intramolecular cyclization to provide thiazolines 74a/b, which are advanced precursors to halipeptins A and D. 

Although the sulfur trifluoride compounds are generally useful as selective agents for conversion of carbonyl and carboxyl groups to difluoromethylene and trifluoromethyl groups, variations in reaction conditions are often necessary.7 Thus the reaction of aromatic ketones requires heating at 150°. Since the reaction with aliphatic aldehydes and ketones is exothermic, it is advan-... 

Caution Protective gloves shovM be worn when handling diethylamino-sulfur trifluoride because this material can cause severe HF bums. 

Treatment of 53 with DAST [(diethylamino)sulfur trifluoride] in methylene chloride provided 57 in 50% yield. Compound 57 was treated with osmium tetroxide at 5 °C in the presence of NMO (4-methylmopholine N-oxide) for 18 h to provide 58 and 59, which were separated by silica-gel chromatography. Compounds 58 and 59 were treated with sodium periodate at 5 °C for 18 h to provide 60 and 61 respectively. Compounds 60 and 61 were treated with CDsMgl followed by NaB CN to give 62 in 20% and 50% yields, respectively. 

FLIJORINATTON Acetyl hypofluoritc. Cesium fluoroxysulfate. (Diethylamino)-sulfur trifluoride. 

A useful fluorinating reagent. Readily converts the -OH group of an alcohol to -F. Deoxy-Fluor Reagent [bis-(2-methoxyethyl) amino sulfur trifluoride] has been found to be more stable.1... 

Diethylamino)sulfur trifluoride, 110 Formylation (see also Carbonylation) Vilsmeier reagent, 341 Fragmentation reactions Cerium(IV) ammonium nitrate, 67 Copper(II) acetate-Iron(II) sulfate, 85 Lead tetraacetate, 155 Friedel-Crafts alkylation Aluminum chloride, 15... 

Dichloro-2,2-difluoroethylene, 105 (Diethylamino)sulfur trifluoride, 110 Reduction reactions (see also Deoxygenation, Reductive. . . ) of acetals and ketals Dibromoalane, 237 Diisobutylaluminum hydride, 237 Triethylsilane-Tin(IV) chloride, 237 of acetates and other esters to alkanes Nickel boride, 197 Triphenylsilane, 334 of acyl halides to alcohols Sodium cyanoborohydride-Tin(II) chloride, 280... 

Tributyltin hydride, 316 O-Glycosides Allyl chloroformate, 9 Boron trifluoride etherate, 43 (Diethylamino)sulfur trifluoride, 110 Silver(I) trifluoromethanesulfonate,... 

Tributyltin hydride, 316 Tributyltinlithium, 319 Trichloroacetonitrile, 321 Other carbohydrates (Diethylamino)sulfur trifluoride, 110 Triethyloxonium tetrafluoroborate, 44 Carbonates (see also Enol carbonates) Carbon dioxide, 65 Di-/-butyl dicarbonate, 94 Carboxylic acids (see also Dicarbonyl compounds, Unsaturated carbonyl compounds)... 

Halo sulfur compounds ra-Chloroperbenzoic acid, 112 (Diethylamino)sulfur trifluoride,... 

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trifluoride ( DAST" M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

BICY CLOl 3.3.0]OCTANE-3,7-DlONES Dimethyl 1,3-acetonedicarboxylate. BIS(DIARYLMETHYL) ETHERS (Diethylamino) sulfur trifluoride. 

In the reaction of benzyl 3-azido-5-0-benzoyl-3,6-dideoxy-a-L-talofuranoside (4) with (diethylamino)sulfur trifluoride (DAST) the anomeric alkoxyl group migrated to the C-2 position and a fluorine atom entered into C-l from the P-side to give the 2-benzyl ether 5 having P-l-galacto configuration [101]. Methyl 2-0-benzoyl-5-0-... 

A systematic study of the reaction of different glycos-2- and 3-uloses with (diethylamino)sulfur trifluoride (DAST) was performed480 for the preparation of gem-difluorides. gem-Difluorination of glycos-2-uloses may take place effectively, but only if the neighboring groups have the same configuration, as shown in the following examples. 

Scheme 13. The seleno linkage in 56 and a 1,2-seleno-migration (56—>57) provided access to 2-deoxy-saccharides such as 60 and orthoesters such as 61 (mCPBA, meta-chloro perbenzoic acid DAST, diethylamonium sulfur trifluoride).

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