98777-24-3Relevant articles and documents
Enantioselective Halo-oxy- and Halo-azacyclizations Induced by Chiral Amidophosphate Catalysts and Halo-Lewis Acids
Lu, Yanhui,Nakatsuji, Hidefumi,Okumura, Yukimasa,Yao, Lu,Ishihara, Kazuaki
supporting information, p. 6039 - 6043 (2018/05/14)
Catalytic enantioselective halocyclization of 2-alkenylphenols and enamides have been achieved through the use of chiral amidophosphate catalysts and halo-Lewis acids. Density functional theory calculations suggested that the Lewis basicity of the catalyst played an important role in the reactivity and enantioselectivity. The resulting chiral halogenated chromans can be transformed to α-Tocopherol, α-Tocotrienol, Daedalin A and Englitazone in short steps. Furthermore, a halogenated product with an unsaturated side chain may provide polycyclic adducts under radical cyclization conditions.
Investigation into phenoxonium cations produced during the electrochemical oxidation of chroman-6-ol and dihydrobenzofuran-5-ol substituted compounds
Hong, Mei Peng,Webster, Richard D.
, p. 2169 - 2175 (2008/09/19)
(Chemical Equation Presented) A series of chroman-6-ol and dihydrobenzofuran-5-ol based compounds with structures similar to vitamin E were examined by cyclic voltammetry and controlled potential electrolysis. The compounds displayed characteristic voltammetric features that enabled their electrochemical behavior to be interpreted in relation to the oxidation mechanism for vitamin E. The electrochemical experiments indicated the presence of several oxidized species: cation radicals, phenoxyl radicals, phenoxonium ions, hemiketals, and p-quinones, whose lifetimes varied depending on the extent of methylation of the aromatic ring (R1, R2, R3) and the nature of substituents R4 and R5.
Enantioselective palladium-catalyzed total synthesis of vitamin E by employing a domino Wacker-Heck reaction
Tietze, Lutz F.,Stecker, Florian,Zinngrebe, Julia,Sommer, Konrad M.
, p. 8770 - 8776 (2007/10/03)
An enantioselective total synthesis of vitamin E in which a novel palladium-catalyzed domino reaction was employed as the key step is described. This reaction allows the formation of the chiral chroman framework and the concurrent introduction of part of the side chain of vitamin E. The sequence comprises an enantioselective Wacker cyclization and a subsequent Heck reaction. Accordingly, reaction of alkenylphenol 12 with methyl vinyl ketone (13) in the presence of catalytic amounts of Pd(OTFA)2 (TFA = trifluoroacetate), the enantiopure ligand (S,S)-Bn-BOXAX (8b; Bn = benzyl, BOXAX = 2,2′-bis(oxazolyl)-1,1′-binaphthyl, and p-benzoquinone (9) as an oxidant gives access to chiral chroman 10 with an enantioselectivity of 97% ee in 84% yield. Chroman 10 is then converted into 24 by an aldol condensation reaction with (3R)-3,7-dimethyloctanal (11). Subsequent 1,2-addition of methyllithium, elimination of water, and hydrogenation yields vitamin E.