3295-96-3Relevant articles and documents
Versatile etherification of alcohols with allyl alcohol by a titanium oxide-supported molybdenum oxide catalyst: Gradual generation from titanium oxide and molybdenum oxide
Kon, Yoshihiro,Fujitani, Tadahiro,Nakashima, Takuya,Murayama, Toru,Ueda, Wataru
, p. 4618 - 4625 (2018/09/29)
Etherification using allyl alcohol to produce allyl ether via dehydration is a fundamental technique for producing fine chemicals that can be applied to electronic devices. We demonstrate a sustainable method to synthesize allyl ethers from allyl alcohol with various alcohols up to a 91% yield, with water as the sole by-product. In this reaction, the active catalyst is gradually generated as the reaction proceeds through the simple mixing of TiO2 and MoO3. The dispersion of MoO3 on the spent catalyst has been observed by XRD, HAADF-STEM, and STEM-EDS mapping. This catalyst shows excellent catalytic activity by virtue of the highly dispersed nature of MoO3 supported on TiO2, which is reusable at least five times. According to a mechanistic study including the measurement of XPS of MoO3 on TiO2 and control experiments using SiO2 and Al2O3 supports, the suitable reducibility of MoO3 to coordinate the allyl moiety on TiO2 seems to be a key factor for high-yielding syntheses of various allyl ethers even under heterogeneous reaction conditions. The reaction mechanism is considered to be as follows: σ-allyl species are formed from dehydration of the allyl alcohol, followed by a nucleophilic attack by another alcohol against the σ-allyl carbon to give allyl ethers. The developed catalytic system should be suitable for easily handled syntheses of allyl ethers due to the employment of commercially available MoO3 and TiO2 with halide- and organic solvent-free reaction conditions.
Hypervalent (tert-butylperoxy)iodanes generate iodine-centered radicals at room temperature in solution: Oxidation and deprotection of benzyl and allyl ethers, and evidence for generation of α-oxy carbon radicals
Ochiai, Masahito,Ito, Takao,Takahashi, Hideo,Nakanishi, Akinobu,Toyonari, Mika,Sueda, Takuya,Goto, Satoru,Shiro, Motoo
, p. 7716 - 7730 (2007/10/03)
1-(tert-Butylperoxy)-1,2-benziodoxol-3(1H)-one (1a) oxidizes benzyl and allyl ethers to the esters at room temperature in benzene or cyclohexane in the presence of alkali metal carbonates. Since this reaction is compatible with other protecting groups such as MOM, THP, and TBDMS ethers, and acetoxy groups, and because esters are readily hydrolyzed under basic conditions, this new method provides a convenient and effective alternative to the usual reductive deprotection. Oxidation with 1a occurs readily with C-H bonds activated by both enthalpic effects (benzylic, allylic, and propargylic C-H bonds) and/or polar effects (α-oxy C-H bonds), generating α-oxy carbon-centered radicals, which can be detected by nitroxyl radical trapping. Measurement of the relative rates of oxidation for a series of ring-substituted benzyl n-butyl ethers 2d and 2p-s indicated that electron-releasing groups such as p-MeO and p-Me groups increase the rate of oxidation, and Hammett correlation of the relative rate factors with the σ+ constants of substituents afforded the reaction constant ρ+ = -0.30. The large value of the isotope effect obtained for the oxidation of benzyl n-butyl ether 2d (k(H)/k(D) = 12-14) indicates that the rate-determining step of the reactions probably involves a high degree of benzylic C-H bond breaking. The effects of molecular dioxygen were examined, and the mechanism involving the intermediacy of the tert-butylperoxy acetal 5 and/or the hydroperoxy acetal 32 is proposed. Particularly noteworthy is the finding that (tert-butylperoxy)iodane 1a can generate the tert-butylperoxy radical and the iodine-centered radical 33a, even at room temperature in solution, via homolytic bond cleavage of the hypervalent iodine(III)-peroxy bond.
