Wansheng Liu

Oxidation of hydrazones by hypervalent organoiodine reagents: Regeneration of the carbonyl group and facile syntheses of α-acetoxy and α-alkoxy azo compounds

Abstract Various hydrazone derivatives of α-keto esters were prepared. The carbonyl group was readily regenerated in high yield from phenylhydrazones through oxidative hydrolysis using hypervalent organoiodine(III) reagents—either bis(trifluoroacetoxy)-iodobenzene (BTIB) in aqueous acetonitrile or hydroxy(tosyloxy)iodobenzene (HTIB) in chloroform. α-Acetoxy phenyl- or methylazo compounds were readily synthesized by oxidation of the corresponding hydrazones with iodobenzene diacetate (IBDA) in dichloromethane or acetic acid. α-Methoxy phenyl- or methylazo compounds were also prepared by oxidation of the hydrazones in methanol. The mechanisms of the oxidation reactions are discussed.

The invention of radical reactions. Part XXXVI. Synthetic studies related to 3-deoxy-D-manno-2-octulosonic acid (KDO)☆

Abstract An application of the Barton ester based radical reactions in carbohydrate chemistry is described. The chain-elongation reaction with ethyl α-trifluoroacetoxy acrylate 2 , followed by treatment with phenylhydrazine provided 3-deoxy-α-hydrazono-octulosonates 8a,b , derivatives of KDO and its gluco -isomer in good yield.

The invention of radical reactions. Part XXXVIII. Homologation of car☐ylic acids with acrylamide and synthetic studies of 3-deoxy-D-arabino-2-heptulosonic acid (DAH) and its 4-epimer

Alkyl radicals generated from O-acyl derivatives of N-hydroxy-2-thiopyridone added onto acrylamide at room temperature to form crystalline 2-(2-pyridylsulfanyl)-car☐amides. Desulfurization of the latter by nickel boride at room temperature afforded primary amides in quantitative yield. 3-Deoxy-D-arabino-2-heptulosonic acid (DAH), its 4-epimer, and their derivatives were effectively synthesized from commercial D-ribonolactone by similar radical chemistry.

A new and concise synthesis of 3-deoxy-D-arabino-2-heptulopyranosonic acid (DAH) and derivatives through the radical chemistry of Barton esters

Abstract Barton ester-based radical chemistry was applied in the synthesis of 3-deoxy-D- arabino -2-heptulopyranosonic acid ( DAH ) from commercial D-ribonolactone. The radical reaction with olefin 2 , followed by aqueous work-up, provided the seven-carbon sugar compounds 5 and 6 (3:1) in 60% yield. Removal of the isopropylidene groups from 5 and hydrolysis of the ethyl ester yielded the DAH barium salt quantitatively.

Radical homologation of d-gluconic acid: highly diastereoselective synthesis of d-gluco-KDO derivatives

Abstract d -glucono 1,5-lactone was converted to O-protected d -gluconic acids. The latter were transformed to gluco-KDO derivatives using Barton ester-based radical chemistry with high diastereoselectivity.

Two Carbon Homologation of Carboxylic Acids Using Acrylamide as a Radical Trap

Abstract Photolysis of O-acyl derivatives of N-hydroxy-2-thiopyridone in the presence of acrylamide in dichloromethane furnished crystalline 2-(pyridine-2-thiyl)-carboxamides. Desulfurization of the latter by nickel boride afforded primary amides in excellent yields.

New and Convenient Syntheses of Anhydro-2-alkyl-3-iminothiazolo-[3,2-a]pyridinium Hydroxide Derivatives

Abstract The 2-alkyl derivatives of anhydro-3-trifluoroacetyliminothiazolo[3,2- a ]pyridinium hydroxide were synthesized in quantitative yield by treatment of either 2-(pyridine-2-thiyl)-carboxamides or the corresponding nitriles with trifluoroacetic anhydride in dichloromethane.

Oxidation of 2-phenylhydrazono-γ-butyrolactone: a novel ring expansion rearrangement leading to tetrahydro-1,3-oxazine-2,4-dione derivatives

2-Hydroxy-2-phenylazo-γ-butyrolactone 3a, prepared from oxidation of phenylhydrazone 1a, either decomposes to form α-keto-γ-butyrolactone 2a in 80% yield or rearranges to tetrahydro-1,3-oxazine-2,4-dione derivative 4a in 95% yield under different conditions.