efficiently undergo nucleophilic addition reactions with allylstannanes in the presence of GdCl3·6H2O in acetonitrile under extremely mild reaction conditions to give the corresponding homoallylic alcohols in excellent yields and with high chemoselectivity.
aerobic oxidative cyclization of β,γ-unsaturated hydrazones for the preparation of pyrazole derivatives has been developed. The hydrazonyl radical promoted the cyclization, along with a concomitant C═Cbondcleavage of β,γ-unsaturated hydrazones. This process has been verified via several control experiments, including a radical-trapping study, an 18O-labeling method, and the identification of the possible
highly efficient Pd/Xiang-Phos catalyzedenantioselective carboetherification of alkenyl oximes with either aryl or alkenyl halides, delivering various chiral 3,5-disubstituted and 3,5,5-trisubstituted isoxazolines in good yields with up to 97 % ee. The sterically bulky and electron-rich (S,Rs)-NMe-X2 ligand is responsible for the excellent reactivities and enantioselectivities. The salient features of this
SnCl2-mediated carbonyl allylation of aldehydes and ketones in ionic liquid
作者:Long Tang、Li Ding、Wei-Xing Chang、Jing Li
DOI:10.1016/j.tetlet.2005.11.022
日期:2006.1
In ionicliquid [bmim]BF4, SnCl2·2H2O acts as an inexpensive and efficient metal salt for carbonyl allylation. By applying ionicliquid, some previously reported serious operational problems associated with the SnCl2-mediated allylation reaction are avoided. Furthermore, ketones, which are less reactive than aldehydes, can also be allylated in high yields with this system.
A substituent effect study on the reactivity and steneoselectivity of the Lewis acid mediated addition of allyl- and crotylstannanes to arylaldehydes indicates that the reaction proceeds via a polar antiperiplanar transition state with the exception of 2,4,6-trimethylbenzaldehyde, for which a cyclic pathway competes with the open pathway.