Cyclic Guanidines as Efficient Organocatalysts for the Synthesis of Polyurethanes

Abstract

International audienceA systematic survey of basic/nucleophilic organocatalysts for the polyaddition in bulk of polyols, PEG-600, and PTMO-650, to isophorone diisocyanate (IPDI) has been performed. Guanidines were shown to be very efficient catalysts for the urethane linkage formation. Bicyclic penta-alkylated guanidines such as MTBD led to polyurethane molecular weight and dispersity that are in the range of those observed with tin-based catalysts such as DBTDL. Tetra-alkylated guanidine such as TBD was shown to be a weaker catalyst as compared to pentaalkylated guanidines, as a result of its high reactivity toward isocyanate, resulting in the formation of a less nucleophilic urea. Although the mechanism has not yet been firmly established, these experiments suggest that a nucleophilic-catalysis mechanism, involving the attack of one of the nitrogen of the guanidine onto the unsaturated system of the isocyanate, should not be totally ruled out with such strong Bronsted base catalysts

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

“…1,8-diazabicyclo [5,4,0] undec-7-ene, DBU) have been shown to accelerate the reaction between diols and diisocyanates; however, their overall efficiencies remain low compared to tin catalysts. [28] Landais and Cramail have disclosed very interesting results showing the enhanced catalytic activity of bicyclic pentaalkylated guanidines (MTBD), [29,30] leading to PU molar masses similar to those obtained with tin catalysts. Recently, Destarac and al.…”

“…This confirms a competition between the nucleophilic and basic activations that can be attributed to guanidine compounds as already mentioned by Alsarraf. [29] The use of the adduct (pre-dissolved in 1-mL THF before addition to the macrodiol) as catalyst in the IPDI-PPG reaction resulted in a clear enhancement of the kinetics, as shown in Figure 4. Its catalytic efficiency seems rather similar or even a little higher than that of TMG under these conditions (60 °C); the shapes of all the curves are also quite similar and do not particularly suggest a regeneration of the parent guanidine in the case of the adduct, contrary to Alsarraf's latent catalysts.…”

“…Following the promising results obtained by Alsarraf et al [29,30] and by Maliverney [36], the kinetics of the reaction between IPDI and PPG-2000 was first monitored in the presence of 1 mol% of catalyst (with respect to the NCO groups, i.e. between 0.19 and 0.50 wt%) chosen among five different guanidine derivatives with different basicities [37][38][39] (see Table 1 in supporting information).…”

Polyurethane-coated silica particles with broad-spectrum antibacterial properties

“…[28][29][30] Moreover, the polymer is relatively low cost, and the material properties are easily tailored through structural variation of the monomers. 31,32 Thus, it would be highly desirable to prepare polyurethane-coated silica particles with antibacterial properties as a direct and cost-effective approach for water/air purification.…”

Guanidines from ‘toxic substances’ to compounds with multiple biological applications – Detailed outlook on synthetic procedures employed for the synthesis of guanidines

“…Guanidines were shown to be very efficient catalysts for the urethane linkage formation. [166] A novel library of chiral guanidines featuring a tartaric acid skeleton was developed from diethyl L -tartrate, by Wang and group in 2013. These guanidines are easily accessed with tunable steric and electronic properties.…”