Lewis base catalysis proved to be more efficient, and the highest asymmetric induction for allylation of ortho-fluorobenzaldehyde reached 82 % ee, which is comparable to other used catalytic conditions. In cases of ortho-vinylbenzaldehyde, the Keck allylation provided the product in 88 % ee. An enantioenriched homoallylicalcohol was used as the starting material for the synthesis of a sertraline
我们报告了在路易斯碱(N,N-二氧化物)、路易斯酸(凯克烯丙基化)和布朗斯台德酸催化下邻位取代苯甲醛烯丙基化的系统研究。邻-卤代苯甲醛被用作醛底物,并特别关注邻-乙烯基和炔基苯甲醛,它们可能作为有趣的合成子用于制备更复杂的手性化合物。在催化条件下实现了类似的对映选择性。在邻卤苯甲醛的情况下,路易斯碱催化被证明更有效,邻氟苯甲醛烯丙基化的最高不对称诱导达到 82% ee,与其他使用的催化条件相当。在邻乙烯基苯甲醛的情况下,Keck 烯丙基化提供 88% ee 的产物。
Synthesis of Biaryl Compounds Using Tandem Ruthenium-Catalyzed Ring-Closing Metathesis
Tandem ring‐closing enyne metathesis (RCEM)/ring‐closing olefin metathesis (RCM) of tetraenynes with Grubbs second‐generation catalyst, followed by elimination, was found to be a new and efficient synthetic approach to biaryl compounds. A preliminary asymmetric version of this approach, which used homochiral Ru–alkylidene catalysts, is also presented.
The synthesis of several natural products’ frameworks is carried out by means of a diastereoselective intramolecular Pauson–Khand reaction promoted by molecular sieves. Diastereoselectivity is achieved only if a coordinating group is present at a convenient distance from the alkene moiety. Naphthalenes can be obtained directly under refluxing toluene conditions.
experimental conditions have been developed for an efficient catalyticPauson–Khandreaction. These are based on the use of a mixture of molecular sieves and tert-butanol as inducers of the process. This mixture, with the appearance of a paste, is able to adsorb CO, thus improving the conversion and making it possible to effect the reactions in the absence of a CO atmosphere. The protocol is applied