Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan.
J Am Chem Soc. 2021 Nov 10;143(44):18400-18405. doi: 10.1021/jacs.1c10109. Epub 2021 Oct 29.
We report herein a zinc-catalyzed β-allylation of cyclopropanols with Morita-Baylis-Hillman (MBH) carbonates with retention of the cyclopropane ring. The reaction is promoted by a zinc aminoalkoxide catalyst, affording cyclopropyl-fused α-alkylidene-δ-valerolactone derivatives in moderate to good yields. Mechanistic experiments suggest that the present reaction does not proceed via direct β-C-H cleavage of the cyclopropanol, but involves zinc homoenolate and its enolization to generate a key bis-nucleophilic species. α-Allylation of this "enolized homoenolate" with MBH carbonate would be followed by regeneration of the cyclopropane ring and irreversible lactonization. The enolized homoenolate mechanism has also been proven to allow for β-functionalization with alkylidenemalononitrile as the reaction partner. A sequence of the present reaction and known cyclopropanol transformation provides an opportunity to transform a simple cyclopropanol into α,β- or β,β-difunctionalized ketones.
我们在此报告了一种锌催化的环丙醇与 Morita-Baylis-Hillman（MBH）碳酸酯的 β-烯丙基化反应，保留了环丙烷环。该反应由锌氨基醇盐催化剂促进，以中等至良好的收率得到了环丙基稠合的α-亚烷基-δ-戊内酯衍生物。机理实验表明，该反应不是通过环丙醇的直接β-C-H 断裂进行的，而是涉及锌偕胺肟和其烯醇化生成关键的双亲核物种。该“烯醇化偕胺肟”与 MBH 碳酸酯的α-烯丙基化反应，随后是环丙烷环的再生和不可逆的内酯化。烯醇化偕胺肟机理也被证明允许与亚甲基丙二腈进行β-官能化反应。本反应序列和已知的环丙醇转化为将简单的环丙醇转化为α,β-或β,β-二官能化酮提供了机会。
