Regio- and Stereoselective Cyclopolymerization of Functional 1,6-Heptadiynes and 1,5-Hexadiynes: Rationalizing Catalyst Activity with Monomer Structure
Final Report Abstract
1. The cyclopolymerization propensity of various 1,6-heptadiynes, 4-aza-1,6- heptadiynes and 4-thia-1,6-heptadiynes by modified Grubbs-Hoveyda initiators has been explored and confirmed. 2. The presence of heteroatoms in the 4-position of 1,6-heptadiynes, e.g., of N or S results in an intermediary coordination to the metal center. Concomitantly, polymerization is either shut down and cyclization occurs instead, or ß-insertion occurs to a significant extent. 3. The examples demonstrated are the first ß-insertions in the Ru-alkyidene-triggered cyclopolymerization of 1,6-heptadiynes. 4. Consequently, quaternization of the amine or substitution by electron withdrawing groups such as aryl groups reduces this coordination to the metal center and allows for the cyclopolymerization of these monomers. 5. Schrock initiators can be tuned to a significant extent and allow for the quantitative cyclopolymerization of most 1,6-heptadiynes, however, in order to obtain high regioselectivity in insertion, a careful tuning is required. Correlations between the initiator’s structure and the mode of insertion have been carried out. “Pseudo-halide” derivatives of Schrock initiators cannot compete with tuned Grubbs-Hoveyda type initiators in terms of activity and selectivity in cyclopolymerization. 6. The cyclopolymerization of various 1,6-heptadiynes including ionic ones by the action of modified Grubbs-Hoveyda initiators can be accomplished in ionic liquids (ILs). Usually, yields are higher in ILs than in standard organic solvents. The regioslectivity in insertion is preserved. 7. Novel Ru-alkylidens bearing diazepin-2-ylidenes have been prepared. Their cyclopolymerization propensity is comparable to the one of the parent imdiazolin-2-ylidene-derived initiators. 8. Substitution of the two Cl-ligands in a Grubbs-Hoveyda initiator by either isothiocyanate or isocyanate results in highly active cyclopolymerization initiators. 9. A mechanism that explains for the high α-insertion selectivity in cyclopolymerization with modified Grubbs-Hoveyda initiators has been established and more recently been confirmed by quantum chemical calculations. Furthermore, these calculations outline the necessity of substituting the Cl-ligands in the parent Grubbs-Hoveyda initiators by electron-withdrawing groups, e.g., trifluoroacetates. 10. Finally, the cyclopolymerization of 1,6-heptadiynes has successfully been extended to the one of 1,7-octadiynes, a so far unprecedented chemistry. Both modified Grubbs- Hoveyda initiators and tunes Schrock initiators allow for high regioselectivities in insertion. On the contrary, 1,5-hexadiynes cannot be cyclopolymerized, neither by modified Grubbs-Hoveyda- nor by Schrock initiators.
Publications
- "Synthesis, X-ray Structure and Reactivity of m-(CF3COO)2-[Mo(N-2,6-i-Pr2-C6H3)(CHCMe2Ph)(OOCCF3)(Et2O)]2, the First Bis(trifluoroacetate) Derivative of a Schrock Catalyst". J. Organomet. Chem., Vol. 691, 5391- 5396, 2006
M. R. Buchmeiser, D. Wang, S. Naumov, K. Wurst
- "Peculiarities of the RuIV-Alkylidene Triggered Cyclopolymerization of N-(bis(alkyloxy)aryl)-Containing 1,6-Heptadiynes". Macromol. Symp., Vol. 254, 370-374, 2007
C. Schmidt, M. R. Buchmeiser
- "Cyclopolymerization of N,N-Dipropargylamines and N,N-Dipropargyl Ammonium Salts". Macromolecules, Vol. 41, 1919-1928, 2008
Y. S. Vygodskii, A. S. Shaplov, E. I. Lozinskaya, P. S. Vlasov, I. A. Malyshkina, N. D. Gavrilova, P. S. Kumar, M. R. Buchmeiser
- "Factors Relevant for the Regioselective Cyclopolymerization of 1,6-Heptadiynes, N,N-Dipropargylamines, N,N- Dipropargylammonium Salts, and Dipropargyl Ethers by RuIV-Alkylidene-Based Metathesis Initiators". J. Am. Chem. Soc., Vol. 131, 387-395, 2009
P. S. Kumar, K. Wurst, M. R. Buchmeiser
- "Isocyanate- and Isothiocyanate-Derived RuIV-Based Alkylidenes: Synthesis, Structure, and Activity". Chem. Asian J., Vol. 4, 1275-1283, 2009
P. S. Kumar, K. Wurst, M. R. Buchmeiser
- "Novel Cyclopolymerization Derived Conjugated Polyenes: Smart Materials for Electronics and Sensors". NATO Science for Peace and Security Series A. Chemistry and Biology, (E. Khosravi, Y.Yagci, Y. Savelyev, Eds.), 303-317, Klymer, Dordrecht, 2009
M. R. Buchmeiser
- "Ru-Alkylidene Metathesis Catalysts Based on 1,3- Dimesityl-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidenes: Synthesis, Structure, and Activity". Organometallics, Vol. 28, 1785-1790, 2009
P. S. Kumar, M. R. Buchmeiser
- “Cyclopolymerization of N,N-Dipropargyl-3,4- dialkoxyanilines by Schrock and Grubbs-Hoveyda Initiators: Influence of Initiator Structure on the Mode of Insertion”. D. Wang, Macromol. Chem. Phys. 2011
C. Schmidt, M. R. Buchmeiser
(See online at https://doi.org/10.1002/macp.201100211)
