Factors relevant for the regioselective cyclopolymerization of 1,6-heptadiynes, N,N-dipropargylamines, N,N-dipropargylammonium salts, and dipropargyl ethers by Ru(IV)-alkylidene-based metathesis initiators.
The factors relevant for the regioselectivity of insertion of various 1,6-heptadiynes, N,N-dipropargylamines, N,N-dipropargylammonium salts and dipropargyl ethers into different Ru(IV)-alkylidenes, i.e., [Ru(CF(3)COO)(2)(IMesH(2))(CHR), (R = 2,4,5-(MeO)(3)-C(6)H(2) (I1), 2-(2-PrO)-5-NO(2)-C(6)H(3) (I3), 2-(2-PrO)-C(6)H(4) (I4)), [Ru(CF(3)COO)(2)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO(2)-C(6)H(3))] (I2), [Ru(CF(3)COO)(2)(3-mesityl-1-((1'R)-1'-phenylethyl)-imidazolin-2-ylidene)(CH-2-(2-PrO)C(6)H(4))] (I5) and [Ru(C(6)F(5)COO)(2)(IMesH(2))(CH-2-(2-PrO)-C(6)H(4))] (I6), (IMesH(2) = 1,3-dimesitylimidazolin-2-ylidene), is described. (13)C NMR experiments revealed that all polymers synthesized by the action of I1-I6 consisted virtually solely (>95%) of five-membered repeat units, i.e., (cyclopent-1-enylene)-1,2-vinylenes, 3,4-(1H-2,5-dihydropyrrylenium)-3,4-vinylenes, and (2-pentyl-2,5-dihydrofurylene)-3,4-vinylenes, respectively. The (13)C NMR-based assignments were supported by the synthesis of model compounds, i.e., (cyclopent-3-ene-1,1-diyldimethylbis(tris(3,5-dimethoxyphenyl)carboxylate) (MC1) and N-propyl-N-ethyl-2,5-dihydropyrrolium tetrafluoroborate (MC2), as well as by ene-yne cross metathesis reactions of 3-(propargyloxy)-1-octyne (M6) with trimethylallylsilane. In the polymerization of N-ethyl-N,N-dipropargylamine (M9), an intermediate was isolated that sheds light onto the role of heteroatoms in the 4-position of 1,6-heptadiynes in cyclopolymerization. In addition, in the cyclopolymerization of M9 by I4 the product resulting from back-biting has been isolated and explains for the low polymerization propensity of Ru-alkylidenes for N-alkyl-N,N-dipropargylamines.
Kumar
P Santhosh
PS
Leibniz-Institut fur Oberflachenmodifizierung (e. V.) IOM, Permoserstrasse 15, D-04318 Leipzig, Germany.
Wurst
K
K
Buchmeiser
Michael R
MR