Reactivity of dehydroacetic acid in organic synthesis

This review reports the reactivity of dehydroacetic acid, which considered to be a very reactive organic compound. The structure of the title compound was investigated. The condensation reactions with primary amines led to the preparation of a variety of heterocyclic ring systems, including bispyran, pyrazole, thiazole, pyridine, pyrimidine, thiazine, thiazepine, and diazepine ring systems. On the other hand, the condensation reaction with aldehydes led to the formation of 1,5-benzodiazepines, pyran, and pyranopyran heterocyclic ring systems. The reaction mechanisms were discussed. The bibliography includes 130 references.     

Trifluoromethanesulfonic Hydrazides

We succeeded to observe at low temperature in reactions of trifluoromethanesulfonic anhydride and trifluoromethanesulfonyl chloride with hydrazine, phenyl hydrazine, and 1,1-dimethylhydrazine a formation of the corresponding trifluoromethanesulfonic hydrazides that at heating to room temperature decomposed liberating nitrogen and affording trifluoromethanesulfinic acid. 2-Phenyl-2H-1,2,3-triazole-4-carboxylic hydrazide reacted with trifluoromethanesulfonic anhydride to furnish trifluoro-N'-(2-phenyl-2H-1,2,3-triazol-4-ylcarbonyl)methane-sulfonic hydrazide that decomposed at heating with elimination of trifluoromethanesulfinic acid and nitrogen yielding 2-phenyl-2H-1,2,3-triazole-4-carbaldehyde.     

Organotellurinic acid anhydrides as selective oxidants in organic synthesis

Several aryltellurinic acid anhydrides have been compared for their oxidising properties in acetic acid. Very high yields of quinones and disulphides can be obtained under conditions where phenols are not oxidised.     

D-奎尼酸: 一个多用途的手性合成子

综述了D-奎尼酸在各种环状和链状生物活性化合物合成中的应用。奎尼酸分子中特有的顺式γ-羟基羧酸的结构单元提供了区别分子中各种羟基,以及进行其它区域选择性和立体选择性控制的方便途径。奎尼酸的结构特征以及其价廉、易得的优点,使之成为一个有用的而且重要的手性合成子。     

Trifluoromethanesulfonic acid as a catalyst for the formation of dansylhydrazone derivatives

Trifluoromethanesulfonic acid (TFMSA) is presented as a new, efficient catalyst in the pre-column fluorescent derivatization of the 3-ketosteroid budesonide with dansylhydrazine and compared to the commonly used catalyst trifluoroacetic acid. With TFMSA the derivatization reaction may be carried out at room temperature, with a considerably higher reaction rate compared to previously used acids. The chromatograms also show that TMFSA results in less formation of spurious peaks from the reagent. Derivatization of steroid solutions ranging from 0.5 to 64 μM could be performed using identical reaction conditions.     

Triacetic acid lactone as a bioprivileged molecule in organic synthesis

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Use of Trifluoromethanesulfonic Acid in Fischer Glycosylations

Abstract

The Fischer glycosylation₁ is one of the standard reactions in carbohydrate chemistry, in which a reducing sugar is reacted under acid catalysis with a simple alcohol to give a glycoside. Hydrochloric acid is the classical catalyst, but other proton, Lewis acid, or acid form ion echange resins have also been used. Now, the use of trifluoromethanesulfonic acid (triflic acid) as a catalyst is communicated.     

Trifluoromethanesulfonic acid catalyzed isomerization of kinetic enol derivatives to the thermodynamically favored isomers

Trifluoromethanesulfonic acid catalyzed isomerization of kinetic enol derivatives to the thermodynamically favored isomers was developed. Under the present conditions, kinetic enol phosphates, enol acetates and benzoates, and enol sulfonates were smoothly isomerized to produce the corresponding thermodynamically favored isomers in good to excellent yields.     

Electrochemical studies of sulfonates in non-aqueous solvents: Part III. Trifluoromethanesulfonic acid as a strong acid in dipolar aprotic solvents and acetic acid

Dissociation of trifluoromethanesulfonic acid in non-aqueous solvents has been investigated mainly by conductometry and compared with that of p-toluenesulfonic, methanesulfonic, fluorosulfuric and perchloric acids. The solvents used are dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, n-butyronitrile, propylene carbonate, acetonitrile, nitromethane, methyl isobutyl ketone and acetic acid. Trifluoromethanesulfonic acid is completely dissociated in rather basic solvents such as dimethyl sulfoxide, dimethylacetamide and dimethylformamide, while it is associated to some extent in the other solvents, especially in methyl isobutyl ketone and acetic acid. The strength of trifluoromethanesulfonic acid is almost the same as that of perchloric acid in all the solvents. Dissociation constants of the other acids are also obtained.     

Epoxy-silanes in organic synthesis

Stereoselective reactions involving functionalised β,γ epoxysilanes and epoxide-allylsilanes provide a range of synthetically useful transformations.     

Recent Applications of Trifluoromethanesulfonic Anhydride in Organic Synthesis

Trifluoromethanesulfonic anhydride has been widely used in synthetic organic chemistry, not only for the conversion of various oxygen-containing compounds to the triflates, but also for the electrophilic activation and further conversion of amides, sulfoxides, and phosphorus oxides. In recent years, the utilization of Tf₂O as an activator for nitrogen-containing heterocycles, nitriles and nitro groups has become a promising tool for the development of new valuable methods with considerable success. In addition, Tf₂O has been used as an efficient radical trifluoromethylation and trifluoromethylthiolation reagent due to the contained SO₂CF₃ fragment, and significant progress has been made in this area. This review summarizes the recent progress in the applications of Tf₂O in the above two aspects, and aims to illustrate the role and potential application of this reagent in organic synthesis.     

Terpenes in organic synthesis

A seven-step synthesis ofS-(+)-hydroprene (S-1) in 20 % overall yield starting fromS-(+)-3,7-dimethyl-1,6-octadiene (2) of 55+-10 % optical purity is described. The introduction of an optical enhancement step in the synthetic sequence at the stage ofS-(–)-3,7-dimethyl-1-octanol (9) raises the optical purity ofS-1 from 50 % to 80 %.For part 13, see. ref.¹ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 342–348, February, 1993.     

Terpenes in organic synthesis

All four stereoisomers of 2,6-diniethyloctan-1-ol, the nearest precursors of the title formates, were synthesized in five to eight stages, with configurational purity ranging from 41 to 96 %, employing a stereodivergent scheme based on the partial hydrolysis of two pseudoracernic substrates, (2RS,6R)-2,6-dimethyloct-1-yl formate and (2RS,6S)-2,6-di-methyloct-1-yl acetate, in the presence of porcine pancreatic lipase (PPL). Configurations and diastereomeric compositions of the alcohols thus obtained were determined by correlating the latter with (S,S)-4,8-diniethyldecanal, prepared on the basis of enantioselective biohydrogenation of (R)-2,6-dimetliylocta-2,7-dienal with bakers' yeast, and by comparing the [α]_D values of the alcohols with their NMR data and/or with those of their (S)-MTPA derivatives. The attractant potency of stereoisomeric 2,6-diniethyloct-1-yl formates towardsTribolium confusum was found to vary depending on their diastereomeric composition. The configuration at C(6) exerts some influence on the stereoselectivity of the PPL-catalyzed hydrolysis of pseudoracemic 2,6-dimethyloct-1-yl formates.[/p]     

Phase managed organic synthesis 2. A new polymer assisted synthesis of acid anhydrides.

A solid-phase copolymer of 4-vinylpyridine is shown to be a highly effective reagent/ catalyst for the synthesis of acid anhydrides from mixtures containing equimolar quantities of carboxylic acids and acid chlorides. The process may be carried out in batch or column mode.     

Trifluoromethanesulfonic acid-catalyzed solvent-free bisindolylation of trifluoromethyl ketones

A trifluoromethanesulfonic acid-catalyzed solvent-free bisindolylation reaction of indoles with alkyl and aryl trifluoromethyl ketones has been developed. The trifluoromethyl-substituted bisindolylalkane derivatives were synthesized in moderate to excellent yields.     

Computer-aided organic synthesis

It is tempting for those in the field of organic synthesis to liken the process of retrosynthesis to a game of chess. That the world chess champion was recently defeated by a computer leads us to think that perhaps new and powerful computing methods could be applied to synthetic problems. Here the analogy between synthesis and chess is outlined. Achievements in the 35-year history of computer-aided synthetic design are described, followed by some more recent developments.