CE07 - Chimie moléculaire

Free-Radical Pathways to Isocyanates – Toward a Green Access to Urethanes and Polyurethanes – NCO-INNOV

Submission summary

The objective of this research program is to develop new methods of access to isocyanates and their derivatives, urethanes and polyurethanes (PU), from cheap and notably bio-sourced raw materials. PU are commodity polymers prepared industrially by adding polyols to polyisocyanates. As the latter are carcinogenic and accessible from highly toxic phosgene, new routes to urethanes and PU must be considered, which will also involve the use of bio-sourced precursors in place of the fossil-based raw materials usually employed.
This isocyanate synthesis project is based on the use of simple and readily available precursors, such as amines and hydrocarbons, and involves activation processes, preferably metal-free, such as photocatalysis under visible, red and near infrared light. The project is organized around 4 main tasks. The first two concern the molecular activation of the above synthons and will be carried out by a team from the ISM at the University of Bordeaux (UB). The third and fourth tasks will consist of an application of the previous methods to the preparation and shaping of polyurethanes and will be developed by LCPO polymer chemists, also at UB.
A new method of access to isocyanates using oxamic acids, generated from the corresponding amines, will thus be considered in a first step (WP1). The decarboxylation of these substrates will be carried out in the presence of an alcohol, by a photochemical process under near-infrared irradiation in order to allow better light penetrability and thus easier scale-up. This approach should provide an easy access to the corresponding urethanes without isolation of the intermediate isocyanate. Two approaches will be tested using a variety of photocatalysts, one based on a process called Triplet-triplet Annihilation - Upconversion (TTA-UC) and another using near infrared absorbing photocatalysts. A second objective (WP2) will be the activation of C-H bonds through photocatalysis and the incorporation of the NCO (isocyanate) function on the carbon skeleton of alkanes, or more generally of poorly functionalized molecules. To do this, we will use hypervalent iodine-based reagents as radical hydrogen atom transfer agents and to incorporate the NCO unit. In each of these tasks, the transformation will be developed on simple model substrates and then extended to naturally occurring compounds.
Finally, in a third part (WP3), the application of the previous methods to the preparation of polyurethanes (PU) will be considered. The possibility to carry out the decarboxylation of bis-oxamic acids through photocatalysis under infra-red light in the presence of polyols should provide a rapid access to PU, in particular bio-sourced PUs. The interest of this approach lies in the high penetrability of IR, allowing a polymerization in bulk (and even without stirring), but also in the opportunity to use the CO2 released during the process as a blowing agent to access polyurethane foams having multiple properties. The insertion of the NCO unit in C-H bonds will also be developed to access diisocyanate units used later in the production of PU by adding polyols (WP4.1), but also for the post-functionalization of polystyrenes and polybutadienes (WP4.2), in order to get highly functionalized polymers, which cannot be prepared through copolymerization.

Project coordination


The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.



Help of the ANR 395,593 euros
Beginning and duration of the scientific project: October 2020 - 42 Months

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