Tetrabutylammonium tribromide mediated condensation of carboxylic acids with alcohol

The direct condensation of various carboxylic acids and alcohols was achieved efficiently at reflux temperature under a solvent free condition using a catalytic amount of Tetrabutylammonium Tribromide (TBATB). Chemoselective acylation of primary alcohols in presence of secondary alcohols and phenols has been achieved. Steric factors in carboxylic acids played a crucial role during chemoselective acylation of diols. Reaction under a solvent free condition, absence of any dehydrating agent or use of any special techniques for removal of water and higher yields are the important features of this protocol

Mild and eco-friendly chemoselective acylation of amines in aqueous medium

Amines in the form of amine hydrochlorides are efficiently acylated with anhydrides in an aqueous medium on addition of NaHCO3. Both cyclic and acyclic anhydrides react with equal ease with an amine and amines of various stereo-electronic factors react with the same rates with an anhydride. No chromatographic separation is needed for isolation of the acylated product. Reactions in aqueous medium, innocuous by-products and chemoselective acylation of amines in the presence of phenols and thiols have been achieved with high selectivity

Novel DNA fluorescence probes based on N-[5-(11-functionalised-undecylamino)-9H-benzo[a]phenoxazin-9-ylidene]propan-1-aminium chlorides: synthesis and photophysical studies

Fluorescent benzo[a]phenoxazinium chlorides possessing undecylamino chains with functionalised ending-groups (hydroxyl, carboxylic acid and the ester group) as substituents at the 5-position of the heterocycles were successfully synthesised and characterised. These compounds were used in photophysical studies with DNA, and compared to the corresponding analogue with a non-functionalised terminal (methyl group). It was found that the functionalised terminal exerts a dramatic influence on the type of interaction with the hydroxyl group promoting intercalation, while the ester group promotes groove binding.Fundação para a Ciência e a Tecnologia (FCT) - REDE/1517/RMN/2005Fundo Europeu de Desenvolvimento Regional (FEDER) - POCI 201

Synthesis and photophysical studies of new benzo[a]phenoxazinium chlorides as potential antifungal agents

A set of four new benzo[a]phenoxazinium chlorides possessing ethyl, propyl, decyl and tetradecyl groups at the 9-amino function of the heterocycle along with a propyl group at the 5-amino position was efficiently synthesised. These compounds displayed fluorescence with maximum emission wavelengths of 673 and 685 nm, in anhydrous ethanol and water. All the benzo[a]phenoxazines were evaluated against the yeast Saccharomyces cerevisiae in a broth microdilution assay. It was found that their antifungal activity depended on the variation in the lengths of the aliphatic chains. The highest MIC activity of 1.56 µM was obtained for compound 7 comprising a di-alkylated propyl substituent at 9-amino position and a propyl chain at the 5-amino position of the heterocycle core.FEDER-COMPETE-QREN-EUFSEThanks are due to the Fundação para a Ciência e Tecnologia (FCT, Portugal) for financial support to the NMR portuguese network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to the Research Centres CFUM [PEst-C/FIS/UI0607/2011 (F-COMP-01-0124-FEDER-022711)] and CQ/UM [PEst-C/QUI/UI0686/2011 (FCOMP-01-0124-FEDER-022716)]. A post-doctoral grant to B. R. Raju (SFRH/BPD/62881/2009) is also acknowledged to FCT, POPH-QREN, FSE. This work was supported by the strategic programme UID/BIA/04050/2013 (POCI-01- 0145-FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI).ERDFPOPH-QRENCOMPETE202

A new recyclable ditribromide reagent for efficient bromination under solvent free condition

This article does not have an abstract

1,1'-(Ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) as a recyclable catalyst for acylation

1,1′-(Ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) catalyzes the acylation of structurally diverse alcohols, amines, thiols, and phenols with a variety of aliphatic and aromatic anhydrides. Steric factors in substrates as well as anhydrides and solvent play significant role during the formation of acylates. Chemoselective mono acetylation of symmetrical diols, primary hydroxy group over secondary and phenolic group and amines over phenols has been achieved. The compatibility of the protocol has been shown by the survival of different acid sensitive functionalities under the present reaction condition. The solvent, acetone, reacts with EDPBT giving bromoacetone and HBr, thus suppressing the bromination of substrates otherwise amenable to bromination. The reagent EDPBT being devoid of phase transfer property and owing to the high solubility of its precursor 1,1′-(ethane-1,2-diyl)dipyridinium dibromide (EDPDB) in water, it was possible to isolate pure acylates by an aqueous work-up circumventing the need for further purification. The process is superior owing to the recyclability of the reagent. The spent reagent can be recovered, regenerated, and reused without any significant loss

Chemoselective thioacetalisation and transthioacetalisation of carbonyl compounds catalysed by tetrabutylammonium tribromide (TBATB)

Thioacetals and thioketals of various aldehydes and ketones were obtained directly from carbonyl compounds or by a transthioacetalisation process from cyclic O,O-acetals in the presence of dithiols and a catalytic amount of Tetrabutylammonium Tribromide (TBATB). Chemoselective thioacetalisation of aromatic aldehydes containing an electron-donating group in the presence of an aldehyde containing an electron-withdrawing group, aldehydes in the presence of ketones, aliphatic cyclic ketones in the presence of aromatic ketones and less hindered ketones in the presence of more hindered ketones have been achieved. A cyclic acetal containing an electron-donating group has been chemoselectively transthioacetalised in the presence of an acetal having an electron-withdrawing substituent. These selectivities are due to the intrinsic reactivity of the substrate themselves and are independent of the catalyst and reaction conditions. Shorter reaction times, mild reaction conditions, stability of acid sensitive protecting groups, high efficiencies, facile isolation of the desired products and the catalytic nature of the reagent are the attractive features of the present method

Novel Nile Blue derivatives as fluorescent probes for DNA

Cationic dyes based on benzo[a]phenoxazinium chlorides either mono- or disubstituted with ethyl, octyl and dodecyl groups at the amino side chain at the 9-position of the tetracyclic ring, and possessing a propyl group at the 5-amino position were synthesised, characterised and used in photophysical studies with DNA and in agarose gel electrophoresis assays. Photophysical results showed that compounds with diethyl and octyl substituents intercalated DNA above a phosphate dye ratio of 10. All compounds associated with DNA as evidenced by their use as colored markers of migrating DNA bands in agarose gel electrophoresis experiments.Fundação para a Ciência e a Tecnologia (FCT