The Curtius Rearrangement of Acyl Azides Revisited – Formation of Cyanate (R–O–CN)

Abstract

The Curtius rearrangement is a synthesis of isocyanates (R-N=C=O) by thermal or photochemical rearrangement of acyl acides and/or acylnitrenes. The photochemical rearrangement of benzoyl azide is now shown for the first time to pro-[a] Chemistry Scheme 1.

Do one‐step mechanisms always involve simultaneous evolution of electron density? QTAIM/IQA analysis of the Curtius rearrangement

“…We first analyze the migration for the hydrogen atom. The reaction evolves from the reagent to a more stable product through a barrier of 114.9 kJ mol −1 (100.8 kJ mol −1 if ZPE correction is included), in agreement with experimental and theoretical values for Curtius rearrangements (95‐115 kJ mol −1 ) …”

“…The reaction evolves from the reagent to a more stable product through a barrier of 114.9 kJ mol −1 (100.8 kJ mol −1 if ZPE correction is included), in agreement with experimental and theoretical values for Curtius rearrangements (95-115 kJ mol −1 ). [8,24] 3.1 | Geometries and resonance forms for critical points Table 1 shows the main geometrical parameters for the critical points in the path.…”

Study of photochemical transformations of organic azides by matrix isolation techniques and quantum chemistry

“…7, spectrum 2), except for one rather intense band at 1193 cm 71 , which is absent in the calculated spectrum. 38 The results of our investigations 38,40 were reproduced in the study, 119 and the previously unidentified band was assigned to phenyl cyanate (25) produced in a small amount. Therefore, isocyanate 21 and trace amounts of cyanate 25 are the final products.…”

π‐Conjugated Triazenes and Nitriles: Simple Photoinduced Synthesis of Anilides Using Mild and Metal‐Free Conditions

“…Limitations of these traditional methods include the propensity for some activated species, such as acyl chlorides, to undergo hydrolysis, cleavage of existing protecting groups, and other side reactions . Other activated intermediates, like acyl azides, can also produce unwanted isocyanate by‐products via Curtius rearrangement . Finally, the use of some activated species, such as anhydrides, results in the waste of half of the equivalents of the carboxylic acid used (Scheme , eq.…”

“…[13] Other activated intermedi-ates, like acyl azides, can also produce unwanted isocyanate byproducts via Curtius rearrangement. [14] Finally, the use of some activated species, such as anhydrides, results in the waste of half of the equivalents of the carboxylic acid used (Scheme 1, eq. 1).…”