Physicochemical characterisation of novel tetrabutylammonium aryltrifluoroborate ionic liquids.

While there have been many studies on the physicochemical characterisation of ILs, little work has previously been reported on the properties unique to the trifluoroborate anion. Here we have characterised the thermal properties, viscosity, liquid nanostructure and intramolecular interactions of 15 novel aryltrifluoroborate ILs. These ILs all contained a tetrabutylammonium cation paired with either meta- or para-substituted aryltrifluoroborate anions, or di-anionic substituted aryltrifluroborate anions. It was found that of the 15 samples analysed, 4 would technically be considered molten salts as they have melting points greater than 100 °C. Overall the structure-property relationship trends of these samples are similar to those previously reported for alkyl and perfluoroalkyltrifluoroborate ILs which contained K+ or Cs+ cations, with the big difference being the ILs in this study having considerably lower melting points.

Synthesis of enantiopure cyclopropyl esters from (-)-levoglucosenone.

The biorenewable chiral synthon (-)-levoglucosenone has been converted to enantiopure cyclopropyl esters using the base-promoted carbocyclisation of 4,5-epoxyvalerates. This protocol was applied to the enantiospecific synthesis of the GABAc receptor agonist (1R,2R)-trans-2-aminomethylcyclopropanecarboxylic acid ((-)-TAMP) and its enantiomer. The process was also extended to generate 1,1,2- and 1,2,3-trisubstituted cyclopropanes resulting in a formal synthesis of the selective glutamate receptor antagonist PCCG-4.

Synthesis of allo- and epi-inositol via the NHC-catalyzed carbocyclization of carbohydrate-derived dialdehydes.

A synthesis of carbocyclic sugars from carbohydrate-derived dialdehydes using organocatalysis has been developed. Sorbitol, mannitol, and galactitol were converted via 1,6-tritylation, perbenzylation or permethylation, detritylation, and Swern oxidation into 2,3,4,5-tetra-O-alkyl-dialdoses that were cyclized via the benzoin reaction promoted by a triazolium carbene. Manno- and galacto-configured dialdehydes gave predominantly single inosose stereoisomers in up to 75% yield if the mixture was acetylated prior to isolation while the gluco-dialdehyde afforded a mixture of three stereoisomers in 61% overall yield. The inososes were stereospecifically reduced using sodium borohydride and then deprotected to give allo- and epi-inositol in good yield that confirmed the structural and stereochemical assignments.