Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Main Authors: Keshaba N. Parida, Gulab K. Pathe, Shimon Maksymenko, Alex M. Szpilman
• Format: Article
• Language: English
• Published: Beilstein-Institut 2018-05-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: 1,4-diketones; enolates; enolonium species; hypervalent iodine; ketones; umpolung
• Online Access: https://doi.org/10.3762/bjoc.14.84

Due to their closely matched reactivity, the coupling of two dissimilar ketone enolates to form a 1,4-diketone remains a challenge in organic synthesis. We herein report that umpolung of a ketone trimethylsilyl enol ether (1 equiv) to form a discrete enolonium species, followed by addition of as little as 1.2–1.4 equivalents of a second trimethylsilyl enol ether, provides an attractive solution to this problem. A wide array of enolates may be used to form the 1,4-diketone products in 38 to 74% yield. Due to the use of two TMS enol ethers as precursors, an optimization of the cross-coupling should include investigating the order of addition.