33334-31-5Relevant articles and documents
Oxygenation of α-methylstyrene with molecular oxygen, catalyzed by 10-methylacridinium ion via photoinduced electron transfer
Suga, Kyou,Ohkubo, Kei,Fukuzumi, Shunichi
, p. 4339 - 4346 (2003)
Photooxygenation of α-methylstyrene with oxygen occurs efficiently in the presence of 10-methylacridinium perchlorate (AcrH+ClO4-) under visible light irradiation in oxygen-saturated acetonitrile (MeCN) to yield acetophenone as the main oxygenated product. No photoinduced oxygenation of α-methylstyrene occurs in the absence of AcrH+ under otherwise the same experimental conditions. Little photodegradation of AcrH- occurs in the present photocatalytic system, which provides a clean method of photoinduced oxygenation reaction with molecular oxygen, alternate to the ene reaction of singlet oxygen. The photocatalytic oxygenation of α-methylstyrene with oxygen is shown to proceed via photoinduced electron transfer from α-methylstyrene to the singlet excited state of AcrH- (1AcrH+*) on the basis of the fluorescence quenching of 1AcrH+* by α-methylstyrene, the quantum yield determination, and the detection of radical intermediates by laser flash photolysis and ESR measurements.
Visible light-promoted dihydroxylation of styrenes with water and dioxygen
Yang, Bo,Lu, Zhan
, p. 12634 - 12637 (2017/12/02)
An efficient visible light promoted metal-free dihydroxylation of styrenes with water and dioxygen has been developed for the construction of vicinal alcohols. The protocol was operationally simple with a broad substrate scope. The mechanistic studies demonstrated that one of the hydroxyl groups came from water and the other one came from molecular oxygen. Additionally, the β-alkyoxy alcohols could also be obtained using a similar strategy.
Titanium-Catalyzed Diastereoselective Epoxidations of Ene Diols and Allylic Alcohols with β-Hydroperoxy Alcohols as Novel Oxygen Donors
Adam, Waldemar,Peters, Karl,Renz, Michael
, p. 3183 - 3189 (2007/10/03)
β-Hydroperoxy alcohols 1-4 serve as effective tridentate oxygen donors for the highly diastereo-selective, titanium-catalyzed epoxidation of ene diols 5a-e. Thus, in contrast to the bidentate tert-butyl hydroperoxide, the usual oxygen donor employed in Sharpless-type epoxidations and known to work poorly for polyhydroxy substrates, the tridentate β-hydroperoxy alcohols efficiently replace the tridentate epoxy diol products 6a-e in the titanium template and thereby the catalytic cycle is sustained by replenishing with efficacy the loaded complex necessary for the oxygen transfer. Irrespective of the substitution pattern of the double bond or the configuration (erythro versus threo) of the diol functionalities in the ene diol substrate, high diastereoselectivities are observed for the epoxy diol products. The high stereochemical control is due to the rigid transition state for the oxygen transfer, which is imposed by the multiple titanium-oxygen bonding and coordination in the titanium template. The observed erythro selectivity for the ene diol derives from the additional bonding of its homoallylic hydroxy group to the titanium center, which fixes the substrate conformation in such a way that the oxygen atom to be transferred approaches from the side of the allylic oxygen functionality (cf. loaded complex A). This additional binding of the bidentate ene diol in the titanium template is also manifested in the enhanced reactivity of the ene diol versus the monodentate allylic alcohols. Nevertheless, the less reactive allylic alcohols also display a high erythro selectivity, provided these monodentate substrates possess 1,2-allylic strain. For the first time a direct, diastereoselective, and catalytic epoxidation of ene diols has been made available for synthetic applications, without recourse to protection group methodology.
