TY - JOUR

T1 - Comparative Study of the Retention of Catalytic Activity of Halonium and Chalconium Cations in the Presence of Crown Ethers

AU - Путнин, Иван Олегович

AU - Сысоева, Александра Александровна

AU - Коваленко, Алексей Валерьевич

AU - Болотин, Дмитрий Сергеевич

PY - 2025/7/10

Y1 - 2025/7/10

N2 - Previous studies have established that efficient electrophilic activation can be achieved through σ-hole interactions. However, the behavior of σ-hole donors in the presence of sterically demanding nucleophiles, which are ubiquitous in biological systems, remains insufficiently explored. To address this knowledge gap, we performed 1H NMR titrations of four crown ethers with the halogen bond donor dibenziodolium triflate. 15-crown-5 was selected for detailed kinetic studies as the most effective σ-hole acceptor. The Schiff base condensation was monitored by 1H NMR spectroscopy using halonium and chalconium catalysts, both in the presence and absence of 15-crown-5. For comparative purposes, control experiments were conducted with silver triflate as a conventional Lewis acid. The observed rate decrease in the presence of 15-crown-5 was attributed to substrate sequestration by the crown ether. In contrast, AgOTf lost its catalytic activity due to the formation of a 15-crown-5-Ag+ complex. Our results demonstrate that while conventional Lewis acids require carefully optimized reaction conditions, σ-hole donors maintain catalytic activity with bulky nucleophiles. These findings highlight the potential of σ-hole donors as robust organocatalysts.

AB - Previous studies have established that efficient electrophilic activation can be achieved through σ-hole interactions. However, the behavior of σ-hole donors in the presence of sterically demanding nucleophiles, which are ubiquitous in biological systems, remains insufficiently explored. To address this knowledge gap, we performed 1H NMR titrations of four crown ethers with the halogen bond donor dibenziodolium triflate. 15-crown-5 was selected for detailed kinetic studies as the most effective σ-hole acceptor. The Schiff base condensation was monitored by 1H NMR spectroscopy using halonium and chalconium catalysts, both in the presence and absence of 15-crown-5. For comparative purposes, control experiments were conducted with silver triflate as a conventional Lewis acid. The observed rate decrease in the presence of 15-crown-5 was attributed to substrate sequestration by the crown ether. In contrast, AgOTf lost its catalytic activity due to the formation of a 15-crown-5-Ag+ complex. Our results demonstrate that while conventional Lewis acids require carefully optimized reaction conditions, σ-hole donors maintain catalytic activity with bulky nucleophiles. These findings highlight the potential of σ-hole donors as robust organocatalysts.

UR - https://www.mendeley.com/catalogue/4f953657-409c-3149-9808-3cae787de5cb/

U2 - 10.1039/d5ob00584a

DO - 10.1039/d5ob00584a

M3 - Article

VL - 23

SP - 7197

EP - 7205

JO - Organic and Biomolecular Chemistry

JF - Organic and Biomolecular Chemistry

SN - 1477-0520

IS - 30

ER -