In the last decade, N-heterocyclic carbenes (NHCs) have emerged as organic mediators to trigger various polymerization reactions.1This is due to their unique nucleophilic and basic properties that can be finely tuned through their substituent pattern.In this work, we have investigated the reactivity of both 1,3-bis(tert-butyl)imidazol-2-ylidene (NHCtBu) and 1,3-bis-(isopropyl)imidazol-2-ylidene (NHCiPr) towards MMA. The direct 1:1 1,4-nucleophilic addition (top of Figure 1) between a NHC and MMA as Michael acceptor forms a zwitterionic imidazolium enolate.2 It was already reported that 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4 triazol-5-ylidene(TPT) promotes the dimerization of MMA3 (Figure 1, route A). 1,3-Bis(mesityl)imidazol-2-ylidene (NHCMes) selectively forms a single-addition (1:1) product with MMA, whereas NHCtBu directly polymerizes MMA4(routes B and C respectively).In our case, we have observed that NHCiPr yields an unprecedented stable zwitterionic cyclodimer with two molecules of MMA5 (Figure 1, route D). DFT calculations have allowed rationalizing experimental differences between with NHCtBu and NHCiPr. The reactivity of NHCiPr and NHCtButowards miscellaneous (meth)acrylic monomers has been screened experimentally and supported by theoretical considerations  References 1 M. Fevre et al., Chem. Soc. Rev. 2013  , 42, 2142-2172.2 C. Fischer et al., J. Am. Chem. Soc. 2006  , 128, 1472-1473.3 S. I. Matsuoka et al., Org. Lett. 2011  , 13, 3722-3725.4 Y. Zhang et al., Angew. Chem. Int. Ed. 2012  , 51, 2465-2469.5 W. Nzahou Ottou et al., Chem. Eur. J.2014,   DOI: 10.1002/chem.201304492

(Meth)acrylates organopolymerization directly induced by N-heterocyclic carbenes (NHCs)

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.