Tandem Addition β-Lithiation−Alkylation Sequence on α,β-Unsaturated Aldehydes
作者:Norma Sbarbati Nudelman、Graciela V. García
DOI:10.1021/jo005698d
日期:2001.2.1
isotopic exchange reactions and trapping of two intermediates, provide clues on the several mechanistic steps of this new reaction. Extended studies revealed that beta-alkyl-substituted alpha,beta-unsaturated aldehydes and aliphatic lithium reagents did not afford good yields of the tandem reaction products, while aromatic lithium reagents gave good results. The aggregation features of the aryllithium
Substitution of allylic alcohols to form a carboncarbonbond is accomplished by a simple reaction of the allylic alcohol itself with an enoxysilane, catalyzed by [Ir(cod)(PPh3)2]X which is activated by H2 molecule. The anion part X of the complexes plays an important role to enhance the rate and product yields of the reactions. The efficacy of the catalyst increases with switching X in the order of
6,6,6-2H3-2E-Hexenal, leaf-aldehyde, has been synthesized in 45% yield and 99.3% purity by reaction of 3,3,3-2H3-n-propyl magnesium bromide with an ethereal solution of 3-trimethylsiloxy-2-propenal (3) prepared in situ. This new one pot procedure alleviates the need to isolate (3) and should prove useful in the synthesis of other E-α,β-unsaturated aldehydes.