Polymeric and Macrocyclic Ureas Based on Meta-Substituted Aromatic Diamines

Abstract

The condensation reactions of the structurally similar monomers 1,3-phenylenediamine (1a) and 2,6-diaminopyridine (1b) with N,N-carbonyldiimidazole have been compared. Whereas the reaction of 1a resulted in an amino terminated oligomeric polyurea, a mixture of two macrocyclic trimers and one macrocyclic tetramer was obtained in the case of 1b. The three components of the mixture could be isolated by extraction with DMSO at different temperatures. The structure of the macrocyclic compounds was investigated by means of NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy.

Formamidine Ureas as Tunable Electrophiles

“…[7] Recently, well-defined polymeric structures containing large numbers of amidine groups were reported. [8] The uses of formamidines in organic synthesis have been quite diversified, including such roles as auxiliaries in asymmetric synthesis, [9] protecting groups for primary amines, [10] electrophiles, [11] and linkers in solid-phase synthesis. [12] General routes to formamidines and related compounds are dominated by condensation (amine + formamide) [13] and exchange (amine + formamidine acetals) [10,14] processes.…”

Formation of Oligomeric and Macrocyclic Ureas Based on 2,6-Diaminopyridine

“…23 Surprisingly, the 1 H NMR spectra of the reaction products based on dimer 1 (see Figure 1) and 2,6diaminopyridine, 23 respectively, do not differ strongly from each other. These are exactly the same reaction conditions as used earlier for the conversion of 2,6-diaminopyridine.…”

“…These are exactly the same reaction conditions as used earlier for the conversion of 2,6-diaminopyridine. 23 Moreover, the residual water in the solvent is not involved in the exchange process, that is, no fast proton exchange but conformational exchange causes NH signal broadening. Three doublet signals at 7.22, 7.26 as well as 7.46 ppm and a signal group of three overlapping triplets centred at 8.29 ppm can be assigned to the protons of pyridine rings.…”

“…The latter can be achieved in the presence of a suitable hydrogen-bonding complement, such as naphthyridyl templates. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The approach described here is based on our earlier study 23 dealing with the synthesis of polymeric and macrocyclic ureas based on aromatic diamines. They found that these materials formed closed cyclic structures rather than oligomers by intramolecular hydrogen bonding.…”

Rational design of all organic polymer dielectrics

“…For each predicted structure, the calculated values of the band gap (E g ), total (E t ) and electronic (E e ) part of dielectric constants are also listed. efforts 39 . Measurements were performed on pressed pellets of the synthesized polymers.…”