Rhodium(III)-Catalyzed Regioselective Decarboxylative Cyclization for the Synthesis of 4<i>H</i>-Furo[3,2-<i>c</i>]chromen-4-one Derivatives
作者:Dandan Zha、Hongji Li、Shiqing Li、Lei Wang
DOI:10.1002/adsc.201600974
日期:2017.2.2
This contribution describes a regioselective cyclization of hypervalent iodine reagents (HIR) with propiolic acids in the presence of a rhodium catalyst. The mild decarboxylation can tolerate a wide range of groups and generates 4H‐furo[3,2‐c]chromen‐4‐one derivatives in good isolated yields.
该贡献描述了在铑催化剂存在下用丙酸对高价碘试剂(HIR)的区域选择性环化。轻度的脱羧可以耐受广泛的基团,并以良好的分离产率生成4 H-呋喃[3,2 - c ] chromen-4-one衍生物。
Cyclization of 4-Phenoxy-2-coumarins and 2-Pyrones via a Double C–H Activation
作者:Katrina Mackey、Leticia M. Pardo、Aisling M. Prendergast、Marie-T. Nolan、Lorraine M. Bateman、Gerard P. McGlacken
DOI:10.1021/acs.orglett.6b00751
日期:2016.6.3
Aryl–heteroaryl coupling via double C–H activation is a powerful transformation that avoids the installation of activating groups. A double C–H activation of privileged biological scaffolds, 2-coumarins and 2-pyrones, is reported. Despite the rich chemistry of these molecular frameworks, the yields are very good. Excellent regioselectivity was achieved on the pyrones. This methodology was applied to the synthesis
afford a series of biologically potent fused seven-membered (6–7–6) ring compounds under mild reaction conditions. This reaction was believed to proceed through Friedel–Crafts type sequential carbometallation followed by protonation to produce phenyldibenz[b,f]oxepines. This method was also extended to synthesize seven-membered rings that are fused with coumarins.
Mechanistic studies on the palladium-catalyzed cross-dehydrogenative coupling of 4-phenoxy-2-coumarins: experimental and computational insights
作者:Aisling M. Prendergast、Zhihan Zhang、Zhenyang Lin、Gerard P. McGlacken
DOI:10.1039/c8dt00842f
日期:——
Delineating the mechanistic features of C–H activation in aryl-heteroaryl coupling is an important step in the design of selective, catalytic processes. Herein we use the intramolecular dehydrogenative coupling of 4-phenoxy-2-coumarins as a model study. Computational results and experimental studies suggest that CMD is operative in the cleavage of both C–H bonds, and that the heteroaryl C–H is cleaved
One-pot two-step synthesis of 3-iodo-4-aryloxy coumarins and their Pd/C-catalyzed annulation to coumestans
作者:Niranjan Panda、Irshad Mattan
DOI:10.1039/c7ra12419h
日期:——
efficient protocol for the synthesis of various coumestans from the intramolecular annulation of 3-iodo-4-aryloxy coumarins through C–H activation has been developed. When 3-iodo-4-aryloxy coumarins were treated with 10% Pd/C (0.3 mol% Pd) in the presence of sodium acetate, the corresponding coumestans were produced in good to excellent yield. Reusability of the palladium catalyst was investigated in