Mechanism of the Regio- and Stereoselective Cyclopolymerization of 1,6-Hepta- and 1,7-Octadiynes by High Oxidation State Molybdenum鈥揑midoalkylidene N-Heterocyclic Carbene Initiators

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• 作者：Katharina Herz ; J枚rg Unold ; Johannes H盲nle ; Roman Schowner ; Suman Sen ; Wolfgang Frey ; Michael R. Buchmeiser
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：July 28, 2015
• 年：2015
• 卷：48
• 期：14
• 页码：4768-4778
• 全文大小：644K
• ISSN：1520-5835

文摘

The regio- and stereoselective cyclopolymerization of a series of 1,6-heptadiynes and 1,7-octadiynes, i.e., of 4,4-bis(ethoxycarbonyl)-1,7-heptadiyne (M1), 4-ethoxycarbonyl-4-(1R,2S,5R)-(鈭?-menthyloxycarbonyl-1,6-heptadiyne (M2), (R,S)-4,5-bis((1R,2S,5R)-(鈭?-menthyloxymethylcarboxymethyl)-1,7-octadiyne (M3), and (S,S/R,R)-4,5-bis((1R,2S,5R)-(鈭?-menthyloxymethylcarboxymethyl)-1,7-octadiyne (M4), by the action of the molybdenum鈥搃midoalkylidene N-heterocyclic carbene (NHC) complexes (Mo(N-2,6-Me₂C₆H₃)(CHCMe₂Ph)(OTf)₂(IMesH₂) (I1), Mo(N-2,6-Me₂C₆H₃)(CHCMe₃)(OTf)₂(IMesH₂) (I2), (Mo(N-2,6-Me₂-C₆H₃)(CHCMe₂Ph)(OTf)(OCH(CF₃)₂)(IMesH₂) (I3), Mo(N-2,6-Cl₂C₆H₃)(CHCMe₃)(OTf)₂(IMes) (I4, IMesH₂ = 1,3-dimesitylimidazolidin-2-ylidene, IMes = 1,3-dimesitylimidazolin-2-ylidene) and by the molybdenum鈥搃midoalkylidene monoaryloxide monopyrrolide (MAP) complexes Mo(N-2,6-iPr₂-C₆H₃)(CHCMe₂Ph)(2,5-Me₂-pyrrolide)(O-2,6-Me₂-C₆H₃) (MAP1), Mo(N-2,6-iPr₂-C₆H₃)(CHCMe₂Ph)(2,5-Me₂-pyrrolide)(O-2,6-Mes₂-C₆H₃) (MAP2), and Mo(N-2-tBu-C₆H₄)(CHCMe₂Ph)(2,5-Me₂-pyrrolide)(O-2,6-Mes₂-C₆H₃) (MAP3) is described. With initiators I1鈥?b>I4, high regioselectivity >96% was observed in the polymerization of M1鈥?b>M4, allowing for virtually selective 伪-insertion. These initiators displayed also high stereoselectivity, allowing for all-trans polyenes with up to 96% syndioselectivity. By contrast, the MAP initiators MAP1鈥?b>MAP3 showed poor regioselectivity (26鈥?2% 伪-selectivity). A polymerization mechanism is proposed that explains for the high stereo- and regioselectivity of the Mo鈥搃midoalkylidene NHC complexes.