Current Organic Chemistry - Volume 15, Issue 19, 2011

While microwave dielectric heating had been widely exploited in several organic chemistry areas to accelerate and improve reactions yields, it has not been often applied to phosphorus chemistry since the beginning of the 21th century. Recently, there has been an important increase in the number of reported uses of microwave in several fields of phosphorus chemistry. This review focuses on a literature survey of the uses of microwave “flash heating” in this chemistry area. Where possible, the relative advantages of this methodology will be compared to classical heating.

This review presents a recent progress in coordination and organometallic chemistry of metal complexes of chelating ligands with pyridine backbone, particularly bidentate [PN] and tridentate [PNP] aminophosphine ligands. The preparation of the ligands, their metal complexes, and the subsequent reactivity studies along with structural properties are discussed.

Approaches for the preparation of pyridazines and fused pyridazines are reviewed. Some corrections about errors in the old literature are given and discussed. The %yields of selected examples are optimized.

A new series of organocatalysts able to catalyse Diels-Alder cycloaddition reactions of α,β-unsaturated aldehydes was studied from both synthetic and theoretical perspectives. The importance of the imidazolidinone scaffold and the influence of the functional groups upon the formation of the reactive species was evaluated. Moreover taking into account that all these new organocatalysts gave the exo-cycloadducts as the major isomers with high selectivity a theoretical study was realized to try and define the essential features determining the observed stereochemical preference.

The synthesis of galacturonate disaccharides has been performed from suitable protected monosaccharides. The use of orthogonal protecting groups allowed us to obtain both methyl galacturonates and galacturonic acid precursors as glycosylation donors or acceptors from a unique monosaccharide derivative. The protecting groups used allowed selective introduction of a fatty acid chain to the non-reducing end of a disaccharide. Furthermore, we explored the preparation of galacturonate conjugated to a carrier protein, and determined the number of sugar residues coupled to the protein by MALDI-MS.

Novel Donor-π-Acceptor triphenylamine-based dyes were synthesized and characterized with regard to their photophysical and photoelectrochemical properties by introducing the ethynyl-2-thienyl moiety as spacer (YS-1). The modification of the donor triphenylamine, performed by intodroducing two p-methoxy groups gave the YS-2 dye. Experimental results showed that the UV-Vis absorption spectra changed exhibiting the increasing of the molar extinction coefficient as well as the red-shift in dichloromethane solution. The maximum power conversion efficiency under standard global AM 1.5 illumination for YS-1 was 4.1% rising to 5.3% when the cell was sensitized with YS-2. The interpretation of the improvement and the discussion of the experimental results were corroborated by Time-Dependent Density-Functional Theory calculations, carried out for the photosensitizers in vacuo and in solution. In particular, the effects on the spectroscopic properties of the dyes due to the presence of the solvent and to the common deprotonation of the carboxylic unit in polar solvents have been investigated.

The synthesis and characterisation of new germylated fatty acid methyl esters and fatty alcohols as novel precursors for structured dendritic materials are described. Hydrogermylation of terminal and internal C=C double bonds by arylgermanes occurred under radical initiation using azo-bis-isobutyronitrile (AIBN) and peroxides. The reactivity depends essentially on the double bond position of the fatty derivatives (intern versus extern), the size of the arylgermane and the sensitivity of the Ge-H bond to radical initiators. More challenging hydrogermylation was also performed starting from glyceryl trioleate affording the functionalised germylated triacylglyceride in quantitative yield. In aqueous polar and non-polar solvents, the germylated di- and tri-esters and their alcohol analogues self-assembled into functional nano- and microstructures (nanoparticles, micrometer spheres and lamellar forms). These structures might provide a strategy toward nanostructured materials having bio-mimetic functions or drug delivery applications.