139165-63-2Relevant articles and documents
A procedure for the preparation of Ti-Beta zeolites for catalytic epoxidation with hydrogen peroxide
Tang, Bo,Dai, Weili,Sun, Xiaoming,Guan, Naijia,Li, Landong,Hunger, Michael
, p. 2281 - 2291 (2014)
Ti-Beta zeolite has been successfully prepared via a reproducible and scalable two-step post-synthesis strategy, which consists of creating vacant T sites with associated silanol groups by dealumination of H-Beta and subsequent dry impregnation of the resulting Si-Beta with titanocene dichloride. The mechanism of Ti incorporation into the framework of Beta is investigated by diffuse reflectance infrared Fourier transform (DRIFT) and multinuclear solid-state nuclear magnetic resonance (SSNMR) spectroscopy. Characterization results obtained from diffuse reflectance ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopy (XPS) reveal that the majority of incorporated Ti species exist in the form of isolated tetrahedrally coordinated Ti(iv) in the zeolite framework while a minority exists in the form of isolated octahedrally coordinated Ti(vi) at framework or extra-framework positions. The obtained Ti-Beta zeolites are highly active and selective catalysts for the epoxidation of unsaturated ketones, e.g. 2-cyclohexen-1-one, with hydrogen peroxide as an oxidant. A quasilinear correlation between the epoxidation rate and the number of framework Ti(iv) species could be drawn evidencing that these Ti(iv) species are responsible for the epoxidation activity of the Ti-Beta zeolites under study. The impact of preparation parameters and reaction conditions on the catalytic performances of the Ti-Beta zeolites in the epoxidation of unsaturated organic compounds with hydrogen peroxide is discussed in detail. the Partner Organisations 2014.
Anionic cyclization approach toward perhydrobenzofuranone: Stereocontrolled synthesis of the hexahydrobenzofuran subunit of avermectin
Sha, Chin-Kang,Huang, Shih-Jung,Zhan, Zhuang-Ping
, p. 831 - 836 (2007/10/03)
A facile anionic cyclization approach toward stereocontrolled synthesis of the hexahydrobenzofuran subunit 3 of avermectin is described. As a model study, treatment of iodo compound 7 with n-BuLi at -100°C effected metal-halogen exchange and subsequent anionic cyclization to afford perhydrobenzofuranone 8. For the total synthesis of subunit 3, compound 9 was dihydroxylated to give diol 10. Protection of the hydroxyl groups of diol 10 gave compound 11. Ketone 11 was then converted into the required enone 12 using Saegusa's protocol. On iodination followed by Luche reduction, enone 12 yielded α-iodo allylic alcohol 14, which on alkylation afforded ether 15. Conversion of the ester unit of 15 into a Weinreb amide group followed by anionic cyclization gave enone 17. 1,4-Addition of (MeOCH2)2CuCNLi2 to enone 17 followed by cleavage of the acetal unit afforded ketone 19. Preferential acetylation of the secondary alcoholic function of 19 afforded compound 20. The stereochemistry of 20 is confirmed by single-crystal X-ray analysis. Elimination of HOAc from 20 gave the crucial olefin 21. Hydrolysis of the acetate unit of 21 followed by protection of the resulting alcoholic function yielded tert-butyldimethylsilyl ether 23. Introduction of a hydroxyl group at the ring junction of 23, using Davis's procedure, finally afforded the hexahydrobenzofuran subunit 3.
