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

Abstract

The syntheses of two AB2 monomers, aminodicarboxylic acid (1) and aminodicarbonyl azide (2), and their model reactions for the one-pot synthesis of dendritic aromatic poly(urea-amide)s using the two AB2 monomers were carried out. The model reaction of 2 and p-tolyl isocyanate produced the target urea with two acyl azide groups in 93% yield at 25 °C for 30 min in tetrahydrofuran (THF). The Curtius rearrangement from an acyl azide to an isocyanate was completed at 140 °C for 30 min in THF. The isocyanate produced via the Curtius rearrangement readily reacted with aniline to give a urea compound in 93% yield. p-Tolyl isocyanate selectively reacted with an amine group of 1 to give a urea with end carboxylic acid groups. The end carboxylic acid groups of the urea could be activated with a condensing agent, diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (DBOP), and the condensation of the active amide with 2 provided an amide with acyl azide end groups.

Dendritic Polyurea Polymers

“…Similar to the concept presented by Kumar and Meijer, Okaniwa et al published a related A 2 B building block for branched polyurea synthesis (Figure ). The preparation involves 5 steps, however, the overall yield cannot be specified from the information given in the paper.…”

Microporous polyurethanes: Synthesis and investigation of the mechanism of the pore formation

“…2 was heated in toluene during which it undergoes Curtius rearrangement to form CHDI. The conversion of azide to isocyanate was confirmed by FTIR studies 30. CHDI was directly reacted with TCD‐DM in DMAc at 80 °C to yield polyurethane P‐1 .…”

“…After 0.5 h of the reaction, an aliquot of the reaction mixture was submitted for FTIR analysis. By comparing the FTIR spectra of the acyl azide and the isocyanate, it was found that the peak at 2141 cm −1 corresponding to the CON 3 group is vanished and a new peak at 2261 cm −1 corresponding to the NCO group was observed, which confirmed the formation of isocyanate 30. The clear solution was cooled to –20 °C using an ice–salt bath, and a mixture of TCD‐DM (0.36 g, 1.80 mmol, for polymer P‐1 ) and DBTDL (2 drops) in dry DMAc (2 mL) was added dropwise.…”

Blocked isocyanates: from analytical and experimental considerations to non-polyurethane applications

“…135 More recently, Gody et al used the Curtius rearrangement on an azide containing RAFT agent, and the reaction between an amine and an isocyanate for polymer-polymer coupling. 136 Additionally, the Curtius rearrangement has been further utilized in the afore-mentioned synthesis of dendritic/hyperbranched polymers using blocked isocyanates, with Okaniwa and co-workers producing dendritic poly(amide-urea)s, 137 and Sivakumar and Nasar synthesizing amine and hydroxyl terminated hyperbranched polyurethanes. 138 Another application was shown by Sagi et al who used a blocked isocyanate polymer backbone to produce self-immolative polymers able to be used as molecular sensors.…”