Unexpected Skeletal Rearrangement in the Gold(I)/Silver(I)-Catalyzed Conversion of 7-Aryl-1,6-enynes to Bicyclo[3.2.0]hept-6-enes via Hidden Brønsted Acid Catalysis

详细信息    查看全文

• 作者：Nana Kim ; Rachel E. M. Brooner ; Ross A. Widenhoefer
• 刊名：Organometallics
• 出版年：2017
• 出版时间：February 13, 2017
• 年：2017
• 卷：36
• 期：3
• 页码：673-678
• 全文大小：442K
• ISSN：1520-6041

文摘

Cycloaddition of an isotopically labeled 7-phenyl-1,6-enyne catalyzed by a mixture of LAuCl [L = P(t-Bu)₂o-biphenyl)] and AgSbF₆ forms the corresponding 6-phenylbicyclo[3.2.0]hept-6-ene with concomitant scrambling of the olefinic CPh (C6) and CH (C7) groups of the product. The extent of C6/C7 scrambling was sensitive to the nature of the silver salt and was likewise observed in the cycloaddition of the 7-phenyl-1,6-enyne catalyzed by mixtures of [LAuNCMe]⁺SbF₆^– and Brønsted acids such as HOTf. These observations and low-temperature NMR analysis of organic and organometallic intermediates in the cycloaddition process were in accord with a mechanism for C6/C7 scrambling initiated by protonation of free bicyclo[3.2.0]hept-7-ene to generate a bicyclo[3.2.0]heptyl cation that undergoes reversible alkyl migration, presumably involving bicyclo[4.1.0]- and bicyclo[3.1.1]heptyl cations prior to elimination of the C7 proton.