Role of imine isomerization in the stereocontrol of the Staudinger reaction between ketenes and imines

Experimental and computational studies reveal the importance of isomerization pathways in the Staudinger reaction between ketenes and imines. In the studied cases, the stereochemistry is determined by the pre-cycloaddition isomerization step.

Hermann Staudinger – Organic chemist and pioneer of macromolecules

To commemorate the centenary of the birth of modern polymer science, a review of the life and accomplishments of Hermann Staudinger is given within the framework of the first half of the twentieth century. Staudinger is remembered for his discovery of ketenes and the Staudinger reaction, but his greatest contribution to chemistry was in developing the concept of macromolecules, for which he received the Nobel Prize in 1953.

Controlled Synthesis of Polyphosphazenes with Chain-Capping Agents

N-alkyl phosphoranimines were synthesized via the Staudinger reaction of four different alkyl azides with tris(2,2,2-trifluoroethyl) phosphite. N-adamantyl, N-benzyl, N-t-butyl, and N-trityl phosphoranimines were thoroughly characterized and evaluated as chain-capping compounds in the anionic polymerization of P-tris(2,2,2-trifluoroethoxy)-N-trimethylsilyl phosphoranimine monomer. All four compounds reacted with the active chain ends in a bulk polymerization, and the alkyl end groups were identified by 1H-NMR spectroscopy. These compounds effectively controlled the molecular weight of the resulting polyphosphazenes. The chain transfer constants for the monomer and N-benzyl phosphoranimine were determined using Mayo equation.

The Usefulness of Trivalent Phosphorus for the Synthesis of Dendrimers

Dendrimers are hyperbranched macromolecules, which are synthesized step-by-step by the repetition of a series of reactions. While many different types of dendrimers are known, this review focusses on the use of trivalent phosphorus derivatives (essentially phosphines and phosphoramidites) for the synthesis of dendrimers. The first part presents dendrimers constituted of phosphines at each branching point. The other parts display the use of trivalent phosphorus derivatives during the synthesis of dendrimers. Different types of reactions have been applied to phosphines. The very first examples of phosphorus-containing dendrimers were obtained by the alkylation of phosphines. Then, several families of dendrimers were elaborated by reaction of phosphoramidites. Such a type of reaction is the base of the solid phase synthesis of oligonucleotides; it has been applied in particular for the synthesis of dendrimers constituted of oligonucleotides. Finally, the Staudinger reaction between phosphines and azides afforded different families of dendrimers, and was at the origin of accelerated methods of synthesis of dendrimers. Besides, the reactivity of the P=N-P=S linkages created by this reaction led to very original dendritic structures.

Late-stage ligand functionalization via the Staudinger reaction using phosphine-appended 2,2′-bipyridine

Phosphine-appended-2,2′-bipyridine serves as a platform for late-stage ligand modifications to install a series of functionalized arenes, including those containing Brønsted and Lewis acidic groups.

Synthesis of 1,2,3-Triazole-Containing Furanosyl Nucleoside Analogs and Their Phosphate, Phosphoramidate or Phoshonate Derivatives as Potential Sugar Diphosphate or Nucleotide Mimetics

<p>The synthesis of a variety of novel, rather stable and potentially bioactive nucleoside analogs and nucleotide mimetics based on xylofuranose scaffolds and comprising a 1,2,3-triazole moiety as a surrogate for a nucleobase or a phosphate group is reported. Isonucleosides embodying a 3-<i>O</i>-(benzyltriazolyl)methyl moiety at C-3 were accessed by using the Cu(I)-catalyzed “click” 1,3-dipolar cycloaddition between 3-<i>O</i>-propargyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranose and benzyl azide as the key step. Related isonucleotides comprising a phosphate or a phosphoramidate moiety at C-5 were obtained via 5-<i>O</i>-phosphorylation of acetonide-protected 3-<i>O</i>-propargyl xylofuranose followed by “click” cycloaddition or by Staudinger reaction of a 5ʹ-azido <i>N</i>-benzyltriazole isonucleoside with triethyl phosphite, respectively. Hydroxy, amino- or bromomethyl triazole 5ʹ-isonucleosides were synthesized through thermal cycloaddition between 5-azido 3-<i>O</i>-benzyl/dodecyl-1,2-<i>O</i>-isopropylidene-α-D-xylofuranoses and propargyl alcohol, propargylamine or propargyl bromide, respectively. The regiochemical outcome of the cycloaddition reactions was influenced by nature of the alkyne hetero substituent (alkyne CH₂X substituent). The 5´-isonucleosides were converted into their [(xylofuranos-5-yl)triazolyl]methyl phosphate, phosphoramidate and phosphonate derivatives as prospective sugar diphosphate mimetics by an appropriate method involving treatment with diethyl phosphorochloridate or a Michaelis-Arbuzov reaction. 4-Phosphonomethyl-1-xylofuranos-5ʹ-yl triazoles were converted into 1,2-<i>O</i>-acetyl glycosyl donors and subsequently subjected to nucleosidation with uracil leading to the corresponding uracil nucleoside 5ʹ-(triazolyl)methyl phosphonates, whose structure potentially mimics that of a nucleoside diphosphate. </p> <p><b> </b></p>