The Boron-Catalyzed Polymerization of Dimethylsulfoxonium Methylide. A Living Polymethylene Synthesis
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- 作者：Brett B. Busch ; Manuel M. Paz ; Kenneth J. Shea ; Chad L. Staiger ; Jonathan M. Stoddard ; James R. Walker ; Xian-Zhi Zhou ; and Huide Zhu
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：April 10, 2002
- 年：2002
- 卷：124
- 期：14
- 页码：3636 - 3646
- 全文大小：185K
- 年卷期：v.124,no.14(April 10, 2002)
- ISSN：1520-5126
文摘
Trialkyl and aryl organoboranes catalyze the polymerization of dimethylsulfoxonium methylide(1). The product of the polymerization is a tris-polymethylene organoborane. Oxidation affords lineartelechelic 
-hydroxy polymethylene. The polymer molecular weight was found to be directly proportionalto the stoichiometric ratio of ylide/borane, and polydispersities as low as 1.01-1.03 have been realized.Although oligomeric polymethylene has been the most frequent synthetic target of this method, polymericstar organoboranes with molecular weights of 1.5 million have been produced. The average turnoverfrequency at 120 
C in 1,2,4,5-tetrachlorobenzene/toluene is estimated at >6 × 106 g of polymethylene(mol boron)-1 h-1. The mechanism of the polyhomologation reaction involves initial formation of a zwitterionicorganoborane·ylide complex which breaks down in a rate-limiting 1,2-alkyl group migration with concomitantexpulsion of a molecule of DMSO. The reaction was found to be first order in the borane catalyst and zeroorder in ylide. DMSO does not interfere with the reaction. The temperature dependence of the reactionrate yielded the following activation energy parameters (toluene, 
H
= 23.2 kcal/mol, S = 12.6 caldeg/mol, G = 19.5 kcal/mol; THF, H = 26.5 kcal/mol, S = 21.5 cal deg/mol, G = 20.1 kcal/mol).
-hydroxy polymethylene. The polymer molecular weight was found to be directly proportionalto the stoichiometric ratio of ylide/borane, and polydispersities as low as 1.01-1.03 have been realized.Although oligomeric polymethylene has been the most frequent synthetic target of this method, polymericstar organoboranes with molecular weights of 1.5 million have been produced. The average turnoverfrequency at 120 C in 1,2,4,5-tetrachlorobenzene/toluene is estimated at >6 × 106 g of polymethylene(mol boron)-1 h-1. The mechanism of the polyhomologation reaction involves initial formation of a zwitterionicorganoborane·ylide complex which breaks down in a rate-limiting 1,2-alkyl group migration with concomitantexpulsion of a molecule of DMSO. The reaction was found to be first order in the borane catalyst and zeroorder in ylide. DMSO does not interfere with the reaction. The temperature dependence of the reactionrate yielded the following activation energy parameters (toluene, H = 23.2 kcal/mol, S = 12.6 caldeg/mol, G = 19.5 kcal/mol; THF, H = 26.5 kcal/mol, S = 21.5 cal deg/mol, G = 20.1 kcal/mol).