All Non-Carbon B3NO2 Exotic Heterocycles: Synthesis,Dynamics, and Catalysis

The B₃NO₂ six-membered heterocycle (1,3-dioxa-5-aza-2,4,6-triborinane=DATB), comprising three different non-carbon period 2 elements, has been recently demonstrated to be a powerful catalyst for dehydrative condensation of carboxylic acids and amines. The tedious synthesis of DATB, however, has significantly diminished its utility as a catalyst, and thus the inherent chemical properties of the ring system have remained virtually unexplored. Here, a general and facile synthetic strategy that harnesses a pyrimidine-containing scaffold for the reliable installation of boron atoms is disclosed, giving rise to a series of Pym-DATBs from inexpensive materials in a modular fashion. The identification of a soluble Pym-DATB derivative allowed for the investigation of the dynamic nature of the B₃NO₂ ring system, revealing differential ring-closing and -opening behaviors depending on the medium. Readily accessible Pym-DATBs proved their utility as efficient catalysts for dehydrative amidation with broad substrate scope and functional-group tolerance, offering a general and practical catalytic alternative to reagent-driven amidation.     

4-Hydroxy-2-quinolones. 93. Synthesis and biological properties of 2-hydroxy-4-imino-1,4-dihydroquinoline-3-carboxylic acid N-R-amides

Various methods of synthesizing amides of 2-hydroxy-4-imino-1,4-dihydroquinoline-3-carboxylic acids have been studied. Results of investigations on the antitubercular and antiinflammatory activity of the obtained compounds are discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 542–555, April, 2006.     

取代肉桂酰甘氨酸酯的合成

在N-甲基吡咯烷酮(NMP)促进下,取代肉桂酸(1a^1g)与二氯亚砜(SOCl2)在20℃酰氯化反应0.5 h,再加入甘氨酸乙酯盐酸盐,在40℃下酰胺化反应4 h,n(取代肉桂酸)/n(SOCl2)/n(甘氨酸乙酯盐酸盐)=1.0/1.2/1.4,合成了一系列取代肉桂酰甘氨酸乙酯(2a^2g),其结构经1H NMR、13C NMR、IR和MS(EI)确证。并探讨了NMP促进取代肉桂酰甘氨酸乙酯反应可能的机理。     

Synthesis of new thiazole analogues of pyochelin, a siderophore of Pseudomonas aeruginosa and Burkholderia cepacia. A new conversion of thiazolines into thiazoles

Three pyochelin analogues and their methyl esters all containing a thiazole ring have been synthesised from the same Weinreb amide key intermediate. One of these analogues called HPTT-COOH, a molecule released in the course of pyochelin and yersiniabactin biosynthesis, was efficiently synthesised using a new base induced conversion of the key compound 2′-(2-hydroxyphenyl)-2′-thiazoline-4′-(N-methoxy,N-methyl) carboxamide into 2′-(2-hydroxyphenyl)-2′-thiazole-4′-(N-methoxy,N-methyl) carboxamide.     

Synthesis of modified Weinreb amides: N-tert-butoxy-N-methylamides as effective acylating agents

An efficient preparation of N-methyl-O-tert-butylhydroxylamine hydrochloride has been settled, which allowed the synthesis of modified Weinreb amides. Nucleophilic addition of organolithium and Grignard reagents on these N-tert-butoxy-N-methylamides afforded efficiently the corresponding ketones and reduction with DIBAL furnished the corresponding aldehydes in good yields up to 97%.     

4-hydroxy-2-quinolones. 96. Synthesis and properties of 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid

Alkaline hydrolysis of the ethyl ester of 4-(cyanoethoxycarbonylmethyl)-2-oxo-1,2-dihydroquinoline-3-carboxylic acid is accompanied by decarboxylation with loss of two molecules of CO₂ and leads to 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acid. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 887–893, June, 2006.     

Efficient synthesis of thioesters and amides from aldehydes by using an intermolecular radical reaction in water

The combination of the water-soluble radical initiator, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (VA-044) and the surfactant, cetyltrimethyl-ammonium bromide (CTAB), was found to be the most suitable condition for the effective and direct synthesis of useful active thioesters (pentafluorophenyl thioesters) in water. In addition, the direct amidation of aldehydes was achieved by the addition of the amines to the thioesterification reaction mixture in water.     

Microwave-assisted cleavage of Weinreb amide for carboxylate protection in the synthesis of a (R)-3-hydroxyalkanoic acid

A versatile route for the modular synthesis of (R)-3-hydroxyalkanoic acids, constituents of the naturally biodegradable poly(3-hydroxyalkanoate) polymers, and its application to the synthesis of (R)-3-hydroxydecanoic acid is described. Key steps include a microwave-assisted catalytic transfer hydrogenation and a facile microwave-assisted hydrolysis of an N-methoxy-N-methyl (Weinreb) amide, which enhances the practicality of this protecting group for carboxylic acids.     

4-Hydroxy-2-quinolones. 122. 1-Hydroxy-3-oxo-5,6-dihydro-3H-pyrrolo[3,2,1-<Emphasis Type="Italic">ij</Emphasis>]-quinoline-2-carboxylic acid hetarylamides as potential antitubercular agents

An improved method is reported for the synthesis of a series of 1-hydroxy-3-oxo-5,6-dihydro-3H-pyrrolo[3,2,1-ij]quinoline-2-carboxylic acid hetarylamides. The antitubercular activity of all of the compounds prepared has been studied. The structure-biological activity dependence revealed is discussed. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1023–1033, July, 2007.     

Novel and efficient method for esterification, amidation between carboxylic acids and equimolar amounts of alcohols, and amines utilizing Me2NSO2Cl and N,N-dimethylamines; its application to the synthesis of coumaperine, a natural chemopreventive dieneamide

Various carboxylic esters or amides were prepared in good to excellent yield between carboxylic acids and equimolar amounts of alcohols or amines under very mild conditions (0-45°C; within 3 h) using dimethylsulfamoyl chloride (Me₂NSO₂Cl; 1) combined with N,N-dimethylamines (Me₂NR: 2a; R=Me, 2b; R=Bu). The choice of the sulfamoyl chloride and the amine is crucial for the reaction; that is, sterically uncrowded amines accelerated the present esterification and amidation. This agent had some advantages over methanesulfonyl chloride (3)/amines as for the atom-economy, avoidance of side reactions, and had very high chemoselectivity toward the carboxyl group vs the hydroxyl group; the experiment was performed by the addition of 1 to the mixture of carboxylic acids and alcohols. Application of this method to the synthesis of coumaperine, a chemopreventive natural product, was performed using the present amidation as a key step.