10.1039/b311894k
The research discusses the solvent-free Wittig olefination using stabilized phosphoranes, which is aimed at addressing environmental concerns, safety considerations, and cost containment by reducing the use of solvents in chemical reactions. The study explores the scope and limitations of this procedure, demonstrating that neat mixtures of arene/hetarenecarbaldehydes, alkanals, and alkenals react exothermally with alkyl (triphenylphosphoranylidene)acetates to produce the corresponding alkenes with generally high yields and short reaction times. The research concludes that while most of the phosphoranes used are stable under microwave irradiation, some are not, and that many of the reactions are exothermic, with microwave irradiation being beneficial in certain cases.
10.1016/S0040-4020(01)96078-8
The research focuses on the enantioselective syntheses of D- and L-ribo- and arabino-C,S-phytosphingosines, which are biologically important compounds found in plant sphingolipids and human brain and kidney lipids. The purpose of the study was to develop practical syntheses of these homochiral compounds from (R)-2,3-O-isopropylidene glyceraldehyde, utilizing key steps such as (Z)-selective olefination, selective monobenzoylation, Mitsunobu-type introduction of nitrogen, and osmylation. The conclusions drawn from the research indicate that the method is efficient, using inexpensive reagents and simple conditions suitable for gram-scale synthesis, and it also allows for the preparation of N- and O-protected derivatives, which could be useful for incorporating these compounds into biologically active ceramide and cerebroside structures. Chemicals used in the process include (R)-2,3-O-isopropylidene glyceraldehyde, phosphorane, benzoyl chloride, triphenylphosphine, diethyl azodicarboxylate, phthalimide, N-methyl-morpholine-N-oxide, osmium tetroxide, and various other reagents for protection and deprotection steps, as well as for chromatographic separation and analysis.
