Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

Abstract

The thermal stability of pseudocyclic and cyclic N-heterocycle-stabilized (hydroxy)aryl- and mesityl(aryl)-λ3-iodanes (NHIs) through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is investigated. Peak decomposition temperatures (T peak) were observed within a wide range between 120 and 270 °C. Decomposition enthalpies (ΔH dec) varied from −29.81 to 141.13 kJ/mol. A direct comparison between pseudocyclic and cyclic NHIs revealed high T peak but also higher ΔH dec values for the latter ones. NHIs bearing N-heterocycles with a high N/C-ratio such as triazoles show among the lowest T peak and the highest ΔH dec values. A comparison of NHIs with known (pseudo)cyclic benziodoxolones is made and we further correlated their thermal stability with reactivity in a model oxygenation.

On the Use of Differential Scanning Calorimetry for Thermal Hazard Assessment of New Chemistry: Avoiding Explosive Mistakes

“…There are other thermal hazard tests available, such as accelerating rate calorimetry (ARC), reaction calorimetry, impact sensitivity or explosivity tests, but none are as ubiquitous or simple to use as the humble DSC. Recently, there have been studies seeking to characterise and compare the thermal and process hazards of compound classes, such as peptide‐coupling reagents, oxidisers, N‐heterocyclic iodanes, diazo compounds, and cage alkyl motifs; or processes such as Pd‐catalysed cross‐coupling, TIPS‐EBX and NaH with DMF/DMSO/DMAc …”

Heterocyclic Hypervalent Iodine(III) Compounds with Fused Benziodazole and Tetrazole Rings (I-Substituted Tetrazolo[1,5-b][1,2]Benziodazoles)

“…Certain HV iodine(III) compounds are known for their explosive nature and their exothermic degradation upon heating or even friction, 86 but to the best of our knowledge, systematic studies and correlations between structure and stability have not yet been published. As mentioned, both BIAT-Cl 4 and BIAT-OAc 6 are highly oxidizing.…”

Iodolopyrazolium Salts: Synthesis, Derivatizations, and Applications

“…[52][53][54] Our group is interested in the synthesis and reactivity of N-heterocyclic stabilized iodanes (NHIs) as well as their monovalent iodoarenes as pre-catalysts. [55][56][57][58][59] Recently, we investigated several hydroxy(tosyloxy) species as oxidants, including C-and Nbound pyrazole and indazole derivatives. [57,58] Herein, we want to report the synthesis of cyclic, pyrazole-substituted iodolium salts (benzo [4,5]iodolo [3,2-c]pyrazol-4-ium (bis)triflates) and their versatile utilization as intermediates for pyrazole functionalization strategies as well as their application as potent halogen bonding (XB) donors.…”