Scarpi Dina, Turchi Giovanni, Fazzini Matteo, Favero Lucilla, Occhiato Ernesto G
Dipartimento di Chimica "U. Schiff", Università degli Studi di Firenze, Via della Lastruccia 13, Sesto Fiorentino, Florence 50019, Italy.
Dipartimento di Farmacia, Università degli Studi di Pisa, Via Bonanno 33, Pisa 56126, Italy.
J Org Chem. 2025 May 23;90(20):6743-6754. doi: 10.1021/acs.joc.5c00433. Epub 2025 May 13.
An easy approach to the enantioselective synthesis of five-, six-, and seven-membered ring-fused cyclopentadienes (85-99% ee) is based on the Au(I)-catalyzed cycloisomerization of enantiomerically pure or enriched propargyl vinyl ethers, which occurs with complete central-to-axial-to-central chirality transfer. DFT calculations show that the formation of a nonplanar σ-Au(I)-pentadienyl cation intermediate having a helical configuration, which quickly cyclizes to form the target cyclopentadiene, accounts for the lack of erosion of the initial optical purity. From a synthetic point of view, when the cyclopentadienes are subjected to a quick 1,5- shift and cannot be isolated as pure regioisomers, they can be trapped by suitable dienophiles during or immediately after the gold(I)-catalyzed cycloisomerization to form more complex polycyclic compounds. The synthesis of an enantiomerically pure α-tertiary amine was realized to demonstrate the usefulness of this approach.
一种对映选择性合成五元、六元和七元环稠合环戊二烯（对映体过量率为85-99%）的简便方法基于金（I）催化的对映体纯或富集的炔丙基乙烯基醚的环异构化反应，该反应具有完全的中心-轴向-中心手性转移。密度泛函理论计算表明，具有螺旋构型的非平面σ-金（I）-戊二烯基阳离子中间体的形成，该中间体迅速环化形成目标环戊二烯，这解释了初始光学纯度没有降低的原因。从合成角度来看，当环戊二烯进行快速的1,5-迁移且不能作为纯区域异构体分离时，它们可以在金（I）催化的环异构化过程中或之后立即被合适的亲双烯体捕获，以形成更复杂的多环化合物。实现了对映体纯α-叔胺的合成，以证明该方法的实用性。
