The synthesis of mixed carbonates from alcohols, dialkyl azodicarboxylate and tris(dimethylamino)-phosphine

Removal of Triphenylphosphine Oxide by Precipitation with Zinc Chloride in Polar Solvents

While the use of triphenylphosphine as a reductant is common in organic synthesis, the resulting triphenylphosphine oxide (TPPO) waste can be difficult to separate from the reaction product. While a number of strategies to precipitate TPPO are available, none have been reported to work in more polar solvents. We report here that mixing ZnCl₂ with TPPO precipitates a TPPO-Zn complex in high yield in several common polar organic solvents. The solvent compatibility of this procedure and the reliability of the precipitation in the presence of polar functional groups were examined to show the utility and limitations of this method.

N-Heterocyclic carbene-mediated redox condensation of alcohols

N-Heterocyclic carbenes (NHCs) with a variety of oxidants promote the Mitsunobu-type coupling reactions of alcohols with phenols, carboxylic acids, and phthalimide.

The Mitsunobu reaction in the 21st century

Recent advancements in the condensation of alcohols with pronucleophiles by the Mitsunobu reaction are described.

The HERON reaction — Origin, theoretical background, and prevalence

The origin of the HERON reaction is reviewed from a historical perspective and shown to have its foundation in the unusual properties of bisheteroatom-substituted amides, so-called anomeric amides. The reaction involves migration of anomerically destabilized oxo-substituents on an amide nitrogen to the amide carbon and dissociation of the amide bond. Computational work providing a theoretical basis for the reaction is presented, together with physical organic measurements that support results therefrom. The rearrangement has been observed in a number of chemical transformations of N-alkoxy-N-aminoamides, reactions of 1-acyloxy-1-alkoxydiazenes, N-alkoxy-N-aminocarbamates, N-alkoxyhydroxamic acids, as well as in the gas-phase reactions of N-acyloxy-N-alkoxyamides.Key words: HERON reaction, anomeric amides, rearrangements, hindered esters, concerted reactions.

A safe and mild synthesis of organic carbonates from alkyl halides and tetrabutylammonium alkyl carbonates

A safe and mild procedure for the synthesis of mixed organic carbonates is described. Reaction of commercially available tetrabutylammonium methoxide and ethoxide with carbon dioxide yields the corresponding methyl and ethyl tetrabutylammonium carbonates (TBAMC and TBAEC). The reactions of these new compounds with several different alkyl halides give methyl and ethyl carbonates in high yields. The use of classic toxic and harmful chemicals such as phosgene and carbon monoxide is avoided.