Metal‐Free Synthesis of Functional 1‐Substituted‐1,2,3‐Triazoles from Ethenesulfonyl Fluoride and Organic Azides

The boom in growth of 1,4‐disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the Cu^I‐catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1‐substituted‐1,2,3‐triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click‐inspired protocol for the synthesis of 1‐substituted‐1,2,3‐triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal‐free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1‐substituted‐1,2,3‐triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1‐substituted triazolium sulfonyl fluoride salts.     

Metal-Free Synthesis of Functional 1-Substituted-1,2,3-Triazoles from Ethenesulfonyl Fluoride and Organic Azides

The boom in growth of 1,4-disubstituted triazole products, in particular, since the early 2000’s, can be largely attributed to the birth of click chemistry and the discovery of the Cu^I-catalyzed azide–alkyne cycloaddition (CuAAC). Yet the synthesis of relatively simple, albeit important, 1-substituted-1,2,3-triazoles has been surprisingly more challenging. Reported here is a straightforward and scalable click-inspired protocol for the synthesis of 1-substituted-1,2,3-triazoles from organic azides and the bench stable acetylene surrogate ethenesulfonyl fluoride (ESF). The new transformation tolerates a wide selection of substrates and proceeds smoothly under metal-free conditions to give the products in excellent yield. Under controlled acidic conditions, the 1-substituted-1,2,3-triazole products undergo a Michael addition reaction with a second equivalent of ESF to give the unprecedented 1-substituted triazolium sulfonyl fluoride salts.     

Synthesis of a Trisaccharide Repeating Unit Related to Arabinogalactan-Protein (AGP) Polysaccharides 1

Abstract

Starting from L-arabinose and methyl β-D-galactopyranoside, methyl 2,3,4-tri-O-benzyl-6-O-[2,4,6-tri-O-benzoyl-3-O-(23,5-tri-O-benzoyl-α-L-arabinofuranosyl)-β-D-galactopyranosyl]-β-D-galactopyranoside 10 has been synthesized. Removal of protecting groups gave the methyl glycoside 12 of a trisaccharide representative of a repeating unit of arabinogalactan (AGP) polysaccharides.

     

Lanthanide induced paramagnetic shifts—derivation of equilibrium constants and absolute shifts in Eu(DPM)3 systems

Relationships between the magnitude of induced ¹H NMR shifts and the equilibrium conditions in solutions containing lanthanide shift reagents are discussed and applied to the shifts induced in several organic molecules by Eu(DPM)₃. Evidence that monoadduct formation is the predominant equilibrium in these solutions, and values of absolute shifts and equilibrium constants are reported. The results indicate that a contact mechanism makes the major contribution to the observed shifts in 4-methylpyridine. In the case of 2,4,6-trimethylpyridine the observed shifts are largely pseudocontact in origin.     

Anisotropic surface tension and the liquid drop model

The liquid drop model assumes that the surface tension of all nuclei is isotropic. The consequences of relaxing this assumption are studied. First a macroscopic theory of anisotropic surface tension is presented. Then with a particular choice for the functional form of the surface tension tensor, this theory is applied to a charged liquid drop. A small anisotropy in the surface tension can significantly distort a highly charged drop and lower its fission barrier.     

The role of partial saturation of the λ3 ladder in SF6 absorption under high power infrared laser excitation

A rate process model is developed to interpret the experimental results of Smith, Schmid, Tablas and Kompa on the time and intensity dependence of the infrared absorption of SF₆. In this model incoherent excitation of the λ₃ molecular mode by the processes of absorption and stimulated emission is followed by radiationless energy transfer from a maximum level to an inactive mode heatbath. This achieves control of the level population by an empirical transfer rate parameter. Good theoretical fits of the experiment absorption decays are obtained with values of approximately 0.1 ns.