671 K
16 pp.
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TitleControlled Synthesis of Polyenes by Catalytic Methods. Progress Report, December 1, 1989 -- November 30, 1992
Author(s)Schrock, R. R.
Publication Date1992
Report NumberDOE/ER/13564--11
Unique IdentifierACC0152
Other NumbersLegacy ID: DE92015286; OSTI ID: 5225994
Research OrgMassachusetts Institute of Technology, Cambridge, MA (United States). Department of Chemistry
Contract NoFG02-86ER13564
Sponsoring OrgU.S. Department of Energy (USDOE), Washington, DC (United States)
Subject400201 -- Chemical & Physicochemical Properties; Copolymers; Progress Report; 37 Inorganic, Organic, Physical and Analytical Chemistry; Polyenes; Chemical Preparation; Alkynes; Polymerization; Progress Report; Molybdenum Complexes; Organometallic Compounds
KeywordsChemical Reactions; Complexes; Document Types; Hydrocarbons; Organic Compounds; Organic Polymers; Polymers; Synthesis; Transition Element Complexes
Related Web PagesRichard Schrock, Robert Grubbs, and Metathesis Method in Organic Synthesis
AbstractA more direct approach to polyenes by the direct polymerization of acetylenes has been achieved. We were able to show that polymerization of acetylene itself can be controlled with a well- characterized alkylidene catalyst, but only if a base such as quinuclidine is present in order to slow down the rate of propagation relative to initiation. (Quinuclidine may also stabilize vinylalkylidene intermediates formed in the reaction). Unfortunately, living polyenes were no more stable than isolated polyenes, and so this approach had its limitations. Direct polymerization of acetylene by Mo(CH-t-Bu)(NAr)(O-t-Bu){sub 2} was more successful, but inherent polyene instability was still a problem. The most important result of the past grant period is the finding that dipropargyl derivatives (HC=CCH{sub 2}XCH{sub 2}C=CH; X = CH{sub 2}, C(CO{sub 2}R){sub 2}, SiR{sub 2}, etc.), which have been reported to be cyclopolymerized by various classical catalysts by as yet unknown mechanisms, are polymerized by Mo(CH-t-Bu)(NAr)[OCMe(CF{sub 3}){sub 2}]{sub 2} in dimethoxyethane. We speculate that intramolecular formation of a five-membered ring in the product of {alpha} addition is fast enough to yield another terminal alkylidene on the time scale of the polymerization reaction, while a six-membered ring is formed in a reaction involving a more reaction terminal alkylidene. Either intermediate alkylidene, but most likely the terminal alkylidene, could react with additional monomer to lead to growth of a chain having dangling triple bonds that eventually could be employed to form crosslinks.
671 K
16 pp.
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