Novel acid catalysed 1,4-addition-type ring-opening polymerisation of cyclic phosphorimidates

Imide-Amide Rearrangement of Cyclic Phosphorimidates: A Mechanistic Study

“…The study presented herein finds full support in the experimental data and is in agreement with the previous proposed mechanism for the polymerisation reaction,20 and reflects the importance of the catalyst for the electrophilic activation of the phosphorimidate molecule. However, it also suggests that the reactivity is controlled by the nucleophilicity of the free phosphorimidate.…”

“…In principle the electronic effects which increase the electrophilicity of the carbon atom should also reduce the nucleophilicity of the imidic nitrogen, being the opposite equally true. The complexation of a phosphorimidate molecule with the Lewis acid yields an adduct in which the carbon atoms are more electrophilic than in the free compound, being this the first step (initiation) of the polymerisation reaction 20. The electronic effects of the substituents, both in the free molecule and in the BF 3 adduct, are responsible for the reactivity observed.…”

“…Optimisation of the polymerisation reaction : In a previous paper20 we reported that the rearrangement of cyclic phosphorimidates 6 proceeds by a two‐step process (Scheme ). In the first step compound 6 undergoes a Lewis acid catalysed 1,4‐addition‐type ring‐opening polymerisation with the formation of the stable oligomeric intermediate 3 .…”

“…Our interest in the development of new synthetic pathways for the preparation of chiral cyclic oxaza and diaza phosphoramides suitable for use in asymmetric chemistry, led us to the study of the Lewis acid catalysed imide–amide rearrangement of cyclic phosphorimidates 19. As a result of this work, we recently reported20 the identification of new types of oligomeric organophosphorus compounds 3 and 4 formed by a novel 1,4‐addition‐type ring‐opening polymerisation of cyclic phosphorimidates and, for the first time, evidence of the intermolecular nature of this rearrangement. The oligomeric compound 3 was identified as being a stable intermediate which originates, upon heating, the previously reported21 rearranged product 5 .…”

Imide–amide rearrangement of oxazaphosphorimidates: studies towards the application to the synthesis of chiral Lewis bases

“…An intermolecular mechanism was found for this system and an oligomeric material 3, resulting from a 1,4-addition-type ring-opening polymerisation (ROP) of the cyclic phosphorimidate 1, was identified as being a stable intermediate of the rearrangement reaction, which occurs with retention of configuration at the carbon atom (Scheme 1). 8,9 We have also established that the most probable mechanism for the 'oligomer-monomer' conversion involves an intramolecular nucleophilic attack of the chain oxygen to the phosphorus atom in a SNi chain reaction with P-O bond cleavage and formation of the cyclic product 2. 9 The aim of the work now reported was to further explore the synthetic possibilities of the imide-amide rearrangement as a key step to the preparation of interesting cyclic chiral diazaphosphoramides.…”