21154-16-5Relevant articles and documents
Visible Light Initiated Photosensitized Electron Transfer Cyclizations of Aldehydes and Ketones to Tethered αβ-Unsaturated Esters: Stereoselective Synthesis of Optically Pure C-Furanosides
Pandey, Ganesh,Hajra, Saumen,Ghorai, Manas K.,Ravi Kumar
, p. 5966 - 5973 (1997)
Photosensitized one-electron reductive activation of aldehydes/ketones tethered with activated olefins leads to efficient cyclization to give diastereoselective cycloalkanols in high yield. The activation is promoted by secondary and dark electron transfer from visible light (405 nm) initiated photosensitized electron transfer generated 9,10-dicyanoanthracene radical anion (DCA.-). The DCA.- is produced by electron transfer using either triphenylphosphine (Ph3P) as sacrificial electron donor (PS-A) or 1,5-dimethoxynaphthalene (DMN) as primary electron donor and ascorbic acid as sacrificial electron donor (PS-B), to light-absorbing DCA. The cyclization is suggested to involve ketyl radical intermediate. High trans diastereoselectivity is observed during the formation of cycloalkanols. This cyclization strategy is further extended for the stereoselective synthesis of optically pure C-furanoside (41), starting from naturally occuring L-tartaric acid. The stereochemistry of 41 is suggested based on the single-crystal X-ray diffraction data.
N-bromosuccinimide (NBS) catalyzed highly chemoselective acetalization of carbonyl compounds using silylated diols and pentaerythritol under neutral aprotic conditions
Karimi, Babak,Hazarkhani, Hassan,Maleki, Jafar
, p. 279 - 285 (2007/10/03)
Various types of carbonyl compounds are efficiently converted to their 1,3-dioxanes and pentaerythritol diacetals by the use of either 1,3-bistrimethylsiloxy propane (A) or 1,3-bistrimethylsilanyloxy-2,2- bistrimethylsilanyloxymethyl propane (D) and a catalytic amount of N-bromosuccinimide (3-10 mol%) under essentially neutral aprotic condition, respectively. A variety of functionalities such as both aliphatic and phenolic -OTBDMS, -OMe, -OBz, furan ring, double bonds and more significantly phenolic -OTHP survived under the present reaction condition. The efficient conversion of two α-tertiary ketones to their cyclic acetals was also achieved using the present protocol.
A FACILE CLEAVAGE OF BENZYLIDENE ACETALS WITH DIISOBUTYLALUMINUM HYDRIDE
Takano, Seiichi,Akiyama, Masashi,Sato, Seiji,Ogasawara, Kunio
, p. 1593 - 1596 (2007/10/02)
Benzylidene acetals of 1,2- and 1,3-glycols are easily cleft by diisobutylaluminum hydride in a toluene solution at 0 deg C - room temperature to give the corresponding monobenzyl ethers of the glycols.In general the reaction proceeds excellently in regioselective manner depending on the stereochemical environment.