作者:Jonas J. Koenig、Thiemo Arndt、Nora Gildemeister、Jörg-M. Neudörfl、Martin Breugst
DOI:10.1021/acs.joc.9b01083
日期:2019.6.21
very mild, metal-free reaction conditions using molecular iodine as the catalyst. A variety of different divinyl ketones including aromatic systems undergo the iodine-catalyzed reaction with moderate to very good yields in both polar and apolar solvents. Our mechanistic studies indicate that the Nazarov system is activated through a halogen bond between the carbonyl group and the catalyst, and other
A Cr(salen)-based metal–organic framework as a versatile catalyst for efficient asymmetric transformations
作者:Qingchun Xia、Yan Liu、Zijian Li、Wei Gong、Yong Cui
DOI:10.1039/c6cc06019f
日期:——
A porous Cr(salen)-MOF can serve as an efficient and effective heterogeneous catalyst for a series of important asymmetric transformations including Nazarov cyclization, aminolysis reaction, Diels-Alder and hetero Diels-Alder reactions, resulting...
Original phosphorodithioic acid diesters were prepared according to an improvedsynthesis of 3,3′-disubstituted H8-BINOL derivatives. In preliminary experiments, these new Brønsted acids were tested as organocatalysts in three reactions. They promoted the Nazarov cyclisation with mixed selectivities, the Mannich reaction with good enantioselectivity and they catalyzed efficiently the alkylation of
Stronger acid, higher speed: The pKa values of a range of binol‐derived Brønstedacids of three different types were measured and found to correlate directly with the catalytic properties of the acids: higher rate constants kI were observed for more acidicBrønstedacidcatalysts (see plot; binol=1,1′‐bi‐2‐naphthol).
较强的酸,较高的速度: 测量了三种不同类型的由多元醇衍生的布朗斯台德酸的p K a值,发现与酸的催化性能直接相关:对于更酸性的布朗斯台德,观察到较高的速率常数k I酸催化剂(请参阅图表;二元醇= 1,1'-bi-2-萘酚)。
2,2′-Biphenol/B(OH)<sub>3</sub> Catalyst System for Nazarov Cyclization
A novel catalyst system—a combination of the readily available 2,2′-biphenol with the inexpensive, nontoxic, and eco-friendly B(OH)3—promoted the Nazarov cyclization of activated and inactivated divinyl ketones to afford the corresponding cyclopentenones up to 96% yield under, in a cis-selective manner. Compared with the conventional harsh conditions with hazardous reagents, user-friendly method was established with bench-stable and easy-to-handle reagents.