A systematic study of benzyl cation initiated cyclization reactions
摘要:
A systematic investigation of benzyl cation initiated cyclization reactions to form six-membered carbocycles is presented. The generation of benzyl cations from benzylic bromides, ethers, and alcohols followed by intramolecular capture provided good yields of cyclized products by use of several different cyclization terminators (e.g., phenyl, alkene, beta-keto ester). A study on the effect of changing the electronic nature of substituents para to the benzyl cation showed that even electron-withdrawing substituents such as quaternary ammonium afford high yields of cyclization products. The formation of five- and seven-membered carbocycles was briefly investigated and found to be less general than the formation of the corresponding six-membered carbocycles.
Enantioselective Alkylation of Aldehydes Using Functionalized Alkylboron Reagents Catalyzed by a Chiral Titanium Complex
作者:Ravindra Kumar、Hiroki Kawasaki、Toshiro Harada
DOI:10.1021/ol4019248
日期:2013.8.16
A practical method is developed for the synthesis of enantioenriched functionalized secondary alcohols through catalytic enantioselective alkylation of aldehydes. Functionalized alkylboron reagents, [FG–(CH2)n]3B (FG = Br, TIPSO, PhtN, CO2iPr, and CN) prepared from terminal olefin precursors by hydroboration, undergo enantioselective addition to aldehydes in the presence of a catalytic amount (5 mol
Palladium-catalyzed Dehydrogenative [3+3] Aromatization of Propyl Ketones and Allyl Carbonates
作者:Kenta Koike、Satoshi Ueno
DOI:10.1246/cl.220032
日期:2022.4.5
A Pd-catalyzed dehydrogenative [3+3] aromatization of 3-phenylpropyl ketones and allylcarbonates has been developed. The reaction gives various di- or tri-substituted aromatic ketones. The reaction consisting of five steps efficiently proceeded in a one-batch, one-manipulation setup. The postulated active species, η3-allyl palladium complex, works as a catalyst for triple dehydrogenations and mono