ChemInform Abstract: PHENYL(TRIMETHYLSILYL)KETENE. SOME KETENE REACTIONS WITH DIAZOMETHANE

Brady, William T.; CHENG, T. C.

doi:10.1002/chin.197804273

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“…19−22 As such, our group has focused on silyl ketenes; not only can these molecules be prepared on the gram scale and stored under common conditions because of the stability provided by the β-silicon effect (i.e., hyperconjugation) but the trialkyl silyl group also provides solubility and tunable steric demands. Reactions of silyl ketenes are relatively few: they can react with diazomethanes to form cyclopropanones and cyclobutanones 23 or undergo [2 + 2] cycloaddition with aliphatic aldehydes in the presence of a Lewis acid, forming β-lactones. 24 Alternatively, hydration of silylketenes has been used to prepare the corresponding αsilylated carboxylic acids, 25 and α-silylated esters have been prepared by reaction of silyl ketenes with alcohols in the presence of ZnX 2 (X = Cl, I).…”

Section: ■ Introductionmentioning

confidence: 99%

Oligomerization of Silyl Ketene: Favoring Chain Extension over Backbiting

et al. 2019

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Silyl ketenes provide an interesting class of molecules to be used as building blocks for highly functional molecules and materials, including as monomers in chain growth polymerizations, whereas previous work suggests that both the carbon–carbon and carbon–oxygen double bond of silyl ketenes can undergo polymerization; no selectivity was observed and secondary reactions occurred. Herein, we report the oligomerization of tert-butyldiphenyl silyl ketene, in which polymerization of the carbon–carbon double bond is accompanied by a Brook rearrangement to give a polysilyl enol ether structure. Computational studies support that this oligomer has a rigid rod structure and is highly polarizable, which is of potential value as a dielectric material. Experimentally, the impact of initiator, solvent, and reaction time is evaluated, and product identity is verified by 2D nuclear magnetic resonance studies. In the presence of a solvent and extended reaction times, intrachain backbiting occurs to yield two cyclic small molecules that were isolated and fully characterized, and mechanisms are proposed for their formation. At shorter reaction time or under solvent-free conditions, linear oligomers were isolated, and use of a bifunctional initiator led to the production of oligomers with molecular weight consistent with that expected based on the monomer-to-initiator ratio and percent monomer consumption. This work illustrates that silyl ketenes are intriguing and exciting building blocks for polymers, and ongoing work addresses the characterization of the physical properties of the materials and identifying conditions for the controlled polymerization of the carbon–oxygen double bond.

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Section: ■ Introductionmentioning

confidence: 99%