Highly enantio- and diastereoselective transannular ketone–ene reactions are catalyzed by a new chromium(III) triflate tridentate Schiff base complex. Electronically unactivated keto-olefins undergo heteroene reactions at ambient temperature to afford enantioenriched bicyclic alcohols, common structural motifs in natural products. The kinetic resolution of a configurationally stable planar-chiral cyclodecenone
metal-free catalytic system composed of trityl halides and thioureas has been found to be a convenient source for the generation of trityl cation species, and this cooperative catalytic system was proved to be highly effective for intramolecular carbonyl-ene cyclization and [2+2] cycloadditions.
Conceptually different: This allyltransfer reaction is catalyzed by Lewis acids (LAs) and proceeds atom‐economically by disproportionation of the carbonyl groups through organized oxonia‐Cope transition states (see scheme). A stereoselective [n+4] ring enlargement leads to a variety of macrolides with 9‐ to 16‐membered rings.
概念上的不同:烯丙基转移反应是由路易斯酸(LAs)催化的,并且通过有组织的oxonia-Cope过渡态使羰基歧化,从而在原子经济上进行(参见方案)。立体选择的[ n +4]环扩大会生成具有9至16元环的各种大环内酯类化合物。
hydrogen chloride (HCl) and chiral dual-hydrogen-bond donors (HBDs) is applied successfully to highly enantioselective Prins cyclization reactions of a wide variety of simple alkenyl aldehydes. The optimal chiral catalysts were designed to withstand the strongly acidic reaction conditions and were found to induce rate accelerations of 2 orders of magnitude over reactions catalyzed by HCl alone. We propose