Synthesis of furan derivatives. LXXXIV. Kinetic studies of the curtius rearrangement of 5-substituted 2-furoyl azides and related compounds.

One-Pot Synthesis of Dendritic Poly(amide-urea)s via Curtius Rearrangement. 1. Monomer Syntheses and Model Reactions for the Dendritic Poly(amide-urea)s Synthesis

“…From this slope, the activation energy and the frequency factor were estimated to be 58 kJ/mol and 7.62 × 10 11 /mol·dm 3 ·s, respectively. The activation energy was smaller than the value of mono-azide-substituted aromatic compounds previously reported …”

“…The activation energy was smaller than the value of mono-azidesubstituted aromatic compounds previously reported. 19 The three electron-withdrawing groups of 4 appear to enhance the reactivity of the Curtius rearrangement.…”

Photodecomposition of 1H‐Pyrrole Carbonyl Azides: Direct Observation of Singlet 1H‐Pyrrole Carbonyl Nitrenes and Triplet 1H‐3‐Pyrrylnitrene

“…Continuing our interest in the spectroscopy, structure, and decomposition of acyl azides and the reactivity of involving nitrene intermediates, herein, we report a first‐time full characterization of the two simplest pyrroylazides, namely 1 H ‐pyrrole‐2‐carbonyl azide ( 1 ) and 1 H ‐pyrrole‐3‐carbonyl azide ( 5 ). Prior to this study, the knowledge about both azides is rare, only their melting points ( 1 : 101–102 °C; 5 : 91–93 °C) have been reported . In the meantime, the stepwise photodecomposition of both azides via the intermediacy of novel pyrroylnitrenes ( 2 and 6 ) and pyrrylnitrenes ( 4 and 8 ) has been disclosed in cryogenic matrices (Scheme ), the mechanism of which follows the very recently disclosed stepwise decomposition of 2‐ and 3‐furoyl azides via the intermediacy of furoyl‐ and furyl‐nitrenes …”

The Curtius rearrangement: mechanistic insight and recent applications in natural product syntheses

“…1,2 Since then, this reaction known as Curtius rearrangement or Curtius reaction has been widely used in organic synthesis due to the usefulness of isocyanate intermediates. 3–5 Isocyanates can be readily converted to a range of functionalities including amines, urethanes and ureas by reaction with appropriate nucleophiles such as water, alcohols or amines, respectively (Figure 1). 6,7 These structural motifs frequently occur in natural products, pharmaceuticals and agrochemicals.…”