Switchable Brønsted Acid‐Catalyzed Ring Contraction of Cyclooctatetraene Oxide Towards the Enantioselective Synthesis of Cycloheptatrienyl‐Substituted Homoallylic Alcohols and Oxaborinanes
作者:Jana Sendra、Oriol Salvado、Manuel Pedrón、Efraim Reyes、Tomás Tejero、Elena Fernández、Pedro Merino、Jose L. Vicario
DOI:10.1002/adsc.202300121
日期:——
studied in detail. We have found that the selectivity can be controlled by the acidity of the catalyst and by the temperature, being able to obtain selectively either the cycloheptatriene carbaldehyde product, arising from a single ring-contraction event, or phenylacetaldehyde that is formed after a second ring contraction process. A complete mechanistic picture of the reaction and a rationale behind the
环辛四烯氧化物在温和条件下使用 Brønsted 酸催化进行两个连续环收缩事件的能力已得到详细研究。我们发现选择性可以通过催化剂的酸度和温度来控制,能够选择性地获得由单一环收缩事件产生的环庚三烯甲醛产物,或在第二次环收缩后形成的苯乙醛过程。基于实验和计算数据,提供了反应的完整机理图和催化剂影响背后的基本原理。最后,这种酸催化的环收缩与原位对映选择性烯丙基化反应,在手性磷酸催化剂存在下进行时,会产生富含对映体的环庚三烯基取代的高烯丙醇。通过铜催化的亲核硼化/环化方案,这些同型烯丙基醇也被转化为富含对映体的氧杂硼烷。