Masamichi Shimizu

Nickel‐Catalyzed Homoallylation of Aldehydes and Ketones with 1,3‐Dienes and Complementary Promotion by Diethylzinc or Triethylborane

Regio- and stereoselective homoallylation of saturated aldehydes and ketones to give bishomoallyl alcohols 1,3-anti-1 is achieved with [Ni(acac)2 ] (cat.) and Et2 Zn [Eq. (a)]. This new catalyst system thus complements the previously reported combination of [Ni(acac)2 ] with Et3 B, which offers advantages in the homoallylation of unsaturated and aromatic aldehydes. acac=acetylacetonato.

Novel carbonyl-dependent regioselective allylation via diethylzinc-mediated umpolung of π-allylpalladium

Abstract Palladium-catalyzed allylation of carbonyls (1.1 – 1.5 mmol) with allylic esters 3a-d (1 mmol) in the presence of Pd(PPh 3 ) 4 (0.05 mmol) and Et 2 Zn (2.4 mmol) in THF at room temperature shows marked carbonyl-dependent regioselectivity, providing α-allylation products 5 with benzaldehyde and γ-allylation products 6 with acetone and ethyl acetate.

Unique regio- and stereoselectivity in the allylation of benzaldehyde with 2-substituted allylzincs generated by umpolung of π-allylpalladium

α,β-Disubstituted allylzincs with alkoxycarbonyl as the β-substituent, generated via an umpolung of in situ generated π-allylpalladium by transmetallation with diethylzinc, react with benzaldehyde at the most substituted allylic terminus to provide syn-γ-butyrolactones 4 exclusively, while those with electron-donating Me, i-Pr, or OMOM as the β-substituents react at both allylic termini to give mixtures of syn-2, anti-2 and Z-3. α,β,γ-Trisubstituted allylzincs provide Z,anti-adducts 5 exclusively.