Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Chemical Process Development, Bristol-Myers Squibb, New Brunswick, New Jersey, 08903, USA.
Angew Chem Int Ed Engl. 2021 Oct 18;60(43):23182-23186. doi: 10.1002/anie.202108499. Epub 2021 Sep 17.
The 1,4-diacyloxylation of 1,3-cyclohexadiene (CHD) affords valuable stereochemically defined scaffolds for natural product and pharmaceutical synthesis. Existing cis-selective diacyloxylation protocols require superstoichiometric quantities of benzoquinone (BQ) or MnO , which limit process sustainability and large-scale application. In this report, reaction development and mechanistic studies are described that overcome these limitations by pairing catalytic BQ with tert-butyl hydroperoxide as the stoichiometric oxidant. Catalytic quantities of bromide enable a switch from trans to cis diastereoselectivity. A catalyst with a 1:2 Pd:Br ratio supports high cis selectivity while retaining good rate and product yield. Further studies enable replacement of BQ with hydroquinone (HQ) as a source of cocatalyst, avoiding the handling of volatile and toxic BQ in large-scale applications.
1,3-环己二烯（CHD）的 1,4-二酰氧基化反应为天然产物和药物合成提供了有价值的立体化学定义骨架。现有的顺式选择性二酰氧基化反应需要超化学计量的苯醌（BQ）或 MnO2，这限制了工艺的可持续性和大规模应用。在本报告中，描述了通过将催化 BQ 与叔丁基过氧化氢配对作为化学计量氧化剂来克服这些限制的反应开发和机理研究。催化量的溴化物能够实现从反式到顺式非对映选择性的转变。Pd:Br 摩尔比为 1:2 的催化剂支持高顺式选择性，同时保持良好的反应速率和产物收率。进一步的研究使我们能够用氢醌（HQ）代替 BQ 作为共催化剂的来源，从而避免了在大规模应用中处理挥发性和有毒的 BQ。
