Diastereocontrol in Asymmetric Allyl–Allyl Cross-Coupling: Stereocontrolled Reaction of Prochiral Allylboronates with Prochiral Allyl Chlorides
摘要:
Palladium-catalyzed allyl-ally cross-coupling was investigated with substituted prochiral allylic boronates. These reactions deliver products bearing adjacent stereocenters, and the issue of diastereocontrol is therefore paramount. Under appropriately modified conditions, this allyl allyl coupling strategy was found to apply to a range of substrates, generally occurring with high enantioselectivity (92:8 to >99:1 er) and good diastereoselection (4:1 to 14:1 dr).
reaction of alkylhalides with lanthanum metal have been shown. The reduction of alkyl iodide with 1/3 equiv of lanthanum metal efficiently proceeded to give the corresponding reductive dimerized products along with the formation of reduction and dehydroiodination products. In the case of alkyl bromides and chlorides, the reaction did not proceed under the same reaction conditions as that of alkyl iodides;
Deoxygenative Dimerization of Benzylic and Allylic Alcohols, and Their Ethers and Esters Using Lanthanum Metal and Chlorotrimethylsilane in the Presence of a Catalytic Amount of Iodine and Copper(I) Iodide
作者:Toshiki Nishino、Yutaka Nishiyama、Noboru Sonoda
DOI:10.1246/bcsj.76.635
日期:2003.3
Benzylic and allylic alcohols were deoxygenatively dimerized by a treatment with lanthanum metal and chlorotrimethylsilane in the presence of a catalytic amount of iodine, giving the corresponding coupling products, alkanes, in moderate-to-good yields. This dimerization reaction was dramatically accelerated by the addition of a catalytic amount of copper(I) iodide. Similarly, ethers and esters were
The reaction of 1-arylpropenyl-lithium (1a–c) with t-alkylbromides proceeds by either a nucleophilic substitution or single electron transfer mechanism, the preferred pathway being a function of electronicsubstituenteffects and the absence or presence of tetramethylethylenediamine or hexamethylphosphoramide.
Atmospheric oxygen was used for the first time as an oxidant in metal-catalyzed homocoupling of Grignard reagents. These manganese- or iron-catalyzed reactions are efficient, cheap, and eco-friendly. They are applicable to the large-scale synthesis of symmetrical conjugated compounds.
Oxo-rhenium catalyzed reductive coupling and deoxygenation of alcohols
作者:Gabrielle R. Kasner、Camille Boucher-Jacobs、J. Michael McClain、Kenneth M. Nicholas
DOI:10.1039/c6cc00537c
日期:——
Representative benzylic, allylic and [small alpha]-keto alcohols are deoxygenated to alkanes and/or reductively coupled to alkane dimers by reaction with PPh3 catalyzed by (PPh3)2ReIO2 (1). The newly discovered reductive coupling reaction...