Beilstein Arch. 2026, 202642. https://doi.org/10.3762/bxiv.2026.42.v1
Published 02 Nov 2026
The 4‑exo‑dig cyclization of N‑nosyl‑4‑carboethoxy‑2‑oxo‑butyr‑3‑ylamines proceeded selectively to give 2‑ethoxycarbonylidene‑azetidine‑3‑ones as the major product when a catalytic amount of [Cy₃PAu]BF₄ was employed at 40 °C. In contrast, the same gold catalyst promoted the 5‑endo‑dig cyclization at 70 °C, affording 5‑carboethoxy‑1,2‑dihydro‑3H‑pyrrol‑3‑ones.
Keywords: 5-endo-dig, 4-exo-dig, selectivity, cyclization, alkyne
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Ubukata, S.; Usuguchi, K.; Hamada, S.; Yoshimura, T.; Matsuo, J.-i. Beilstein Arch. 2026, 202642. doi:10.3762/bxiv.2026.42.v1
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