6090-08-0Relevant academic research and scientific papers
Simple, chemoselective hydrogenation with thermodynamic stereocontrol
Iwasaki, Kotaro,Wan, Kanny K.,Oppedisano, Alberto,Crossley, Steven W. M.,Shenvi, Ryan A.
supporting information, p. 1300 - 1303 (2014/02/14)
Few methods permit the hydrogenation of alkenes to a thermodynamically favored configuration when steric effects dictate the alternative trajectory of hydrogen delivery. Dissolving metal reduction achieves this control, but with extremely low functional group tolerance. Here we demonstrate a catalytic hydrogenation of alkenes that affords the thermodynamic alkane products with remarkably broad functional group compatibility and rapid reaction rates at standard temperature and pressure.
Stereocontrolled double ring expansion of fused allylidenecyclopropanes. A novel route to hydroazulenes and other fused bicyclic systems
Shook, Craig A.,Romberger, Matthew L.,Jung, Sang-Hun,Xiao, Manchao,Sherbine, James P.,Zhang, Birong,Lin, Fu-Tyan,Cohen, Theodore
, p. 10754 - 10773 (2007/10/02)
A variety of 1-(phenylthio)-1-(trimethylsilyl)cyclopropanes, fused to five-, six-, and seven-membered rings, have been prepared by several procedures and reductively lithiated by means of aromatic radical anions. The resulting 1-lithio-1-(trimethylsilyl)cyclopropanes have been treated in most cases with α,β-unsaturated aldehydes, followed by potassium tert-butoxide to yield allylidenecyclopropanes. The latter, upon thermal rearrangement either in a sealed tube or in a flash vacuum pyrolysis apparatus, undergo a double ring expansion to cyclopentenocyclohexenes, -cycloheptenes (hydroazulenes), or -cyclooctenes. When the distal double bond of the allylidenecyclopropane possesses a terminal trans substituent, that substituent in the hydroazulene pyrolysis product is predominantly in the exo position (cis to the hydrogen atom at the ring junction carbon atom); cis substituents end up mainly in the endo position. Thus, the ring closure occurs mainly in a conrotatory sense. When the distal unsaturation is incorporated into a ring, a tricyclic system results. Carbonyl functionality can be introduced into either position of the five-membered rings and either of the two carbon atoms adjacent to the ring junction of the seven- or eight-membered ring of the ring expansion products by using appropriately substituted rearrangement substrates. Complete regioselectivity is observed when the original six- or seven-membered ring has a ketone group adjacent to the ring junction; the product is a completely conjugated dienone. Complete regioselectivity in the opposite sense is observed upon rearrangement of the corresponding kinetic silyl enol ether. This methodology is demonstrated by the synthesis of (+)-9-epiledene, containing the gross structural features of the aromadendrene sesquiterpenes, and of (±)-α-bulnesol, a guiazulene sesquiterpene.
