N₂O₄ Chemisorbed onto n‐Propylsilica Kryptofix 21 and Kriptofix 22 as Two New Functional Polymers for the Fast Oxidation of Urazoles and 1,4‐Dihydropyridines

Abstract

3‐Chloropropylsilica was reacted with Kriptofix 21 or 22 in the presence of triethylamine to form N‐propylsilica Kryptofix 21 and Kriptofix 22. Then N2O4 was added to each of these polymers to chemisorb onto cavity of aza‐crown ethers. These functionalized polymers were applied for the fast and simple oxidation of urazoles and 1,4‐dihydropyridines, respectively.

{[[K.18-Crown-6]Br3}n: A tribromide catalyst for the catalytic protection of amines and alcohols

“…In this continuation of our studies on the host-guest chemistry of crown ethers [18,[21][22][23][24] on the synthesis and application of tribromide reagents [18,19,21,22] and the protection of organic functional groups [21,22,25,26], we report that {[K.18-crown-6]Br3}n is an excellent catalyst for the tert-butoxycarbonylation of various amines and TMS and THP of alcohols under mild conditions. Thus, we prepared a range of tert-butoxycarbonylated amines under the following reaction conditions: amines (1 mmol), Diboc (1 mmol), {[K.18-crown-6] Br3}n (0.001 mmol), and ethanol (5 ml) as the optimized solvent for this reaction (Scheme 1 and Table 2).…”

“…Chemicals were purchased from Merck. The protected products were characterized by the comparison of their spectral (IR, 1 H-NMR, and 13 C-NMR) and physical data with those of known samples [21][22][23][24][25][26][27][28]. {[K.18-crown-6]Br3}n was prepared according our previously reported procedure [18].…”

Triazolinediones as Highly Enabling Synthetic Tools

“…However, the resulting solution is contaminated by the crown ether, which can dissolve in the utilized solvent. Therefore, the same strategy was applied using silica-supported functional crown ethers, such as the commercially available Kryptofix 21 and Kryptofix 22, making the oxidation system heterogeneous . The biggest advantage of this solid-supported oxidant is the easy workup by filtration, the enhanced stability of the active species, and the possibility to recover the solid support and retreat it with a N 2 O 4 gas stream.…”