Diethylzinc‐Mediated Allylation of Carbonyl Compounds Catalyzed by [(NHC)(PR
<sub>3</sub>
)PdX
<sub>2</sub>
] and [(NHC)Pd(η
<sup>3</sup>
‐allyl)Cl] Complexes
作者:Alexandre Flahaut、Krimo Toutah、Pierre Mangeney、Sylvain Roland
DOI:10.1002/ejic.200900891
日期:2009.12
reaction was investigated with this complex. [(IMesMe)(PPh3)PdI2] catalyzes the allylation of aromatic (except 4-nitrobenzaldehyde) and aliphatic aldehydes (including enolizable aldehydes) with cinnamyl acetate to give the corresponding homoallylic alcohols in 57–98 % yields and diastereoselectivities ranging from 70:30 to 92:8. The allylation of acetone also takes place under the same conditions, leading
Reinvestigation of the Lewis Acid-mediated Reaction of 3-Aryl-substituted Allyltin Reagents toward Aldehydes. Divergent Stereocontrol of the Product by Lewis Acids
作者:Yutaka Nishigaichi、Akio Takuwa
DOI:10.1246/cl.1994.1429
日期:1994.8
3-Arylallyltin reagents including cinnamyltin stereoselectively gave anti-adducts in the ZnCl2-mediated reaction toward aldehydes in a donating solvent via the 6-membered cyclic transition state. In contrast, the BF3-mediated reaction gave syn-adducts via the acyclic transition state. The present result corrects the previously reported stereochermcal determination of the BF3-mediated product.
cinnamyl halides also showed good diastereoselectivity favoring the anti-product. Mechanistic studies using proton NMR techniques suggested that the additive (i.e., CuCl2, TiCl3, PdCl2) could accelerate the formation of allyltin intermediate, but this step was shown not to be the most important for the allylation. Thus we proposed that the Lewis acid catalysis effect exerted by the additive was the main