ChemInform Abstract: Scope and Limitations in Palladium-Catalyzed Substitution Reactions of Unsaturated Fused Lactones.

✍ Scribed by V. K. AGGARWAL; N. MONTEIRO; G. J. TARVER; R. MCCAGUE

• Publisher: John Wiley and Sons
• Year: 2010
• Weight: 33 KB
• Volume: 28
• Category: Article
• ISSN: 0931-7597
• DOI: 10.1002/chin.199749131

✦ Synopsis

Scope and Limitations in Palladium-Catalyzed Substitution Reactions of Unsaturated Fused Lactones.

-A range of α-substituted lactones of type (I) are prepared in order to study how electronic and steric factors influence the rate of the substitution reaction. The rates are found to increase with increasing electron-withdrawing ability of the substituent and there is a strong correlation between rate and pKa of the corresponding substituted acetic acids, with exception of R1 or R2 = OH. The endo-hydroxy lactone (Ib) reacts much faster than expected, whereas the exo analogue (Ic) reacts much slower than expected. Generally, the reaction rates of the endo isomers are higher than those of the exo isomers. Lactones with unactivated leaving groups like (Ia) undergo efficient coupling with good nucleophiles, whereas with less reactive nucleophiles poor results are obtained. In contrast, lactones with activated leaving groups like (Ib) react efficiently with a broad range of nucleophiles