Copper-mediated synthesis of coumestans via C(sp 2 )-H functionalization: Protective group free route to coumestrol and 4′- O -methylcoumestrol
作者:Mayuri M. Naik、Vijayendra P. Kamat、Santosh G. Tilve
DOI:10.1016/j.tet.2017.07.057
日期:2017.9
A simple and efficient two step synthesis of coumestans is described. The key reaction in the synthesis is the use of easily available Cu(OAc)2 for CH functionalization of 3-(2-hydroxyphenyl)coumarin to give coumestan ring system via formal oxidative cyclization. This approach provided a short protective group free route to naturallyoccurring coumestrol and 4′-O-methylcoumestrol.
A copper-catalyzed intramolecular cross dehydrogenative C–O coupling reaction of 2′-hydroxyl-3-arylcoumarins was developed. This protocol provided a facile and efficient strategy for the construction of natural coumestans and derivatives in moderate to high yields. This transformation exhibited good functional group compatibility and was amenable to substrates with free phenolic hydroxyl groups.
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
A concise and efficient approach to the syntheses of coumestan analogues has been developed. The underpinning strategy involves a FeCl3-mediated direct intramolecular oxidative annellation of 4-hydroxy-3-phenyl-2H-chromen-2-one derivatives. Utilizing this synthetic protocol, a variety of coumestan derivatives were conveniently obtained from readily available reagents.
Palladium(II)-Catalyzed C–H Bond Activation/C–C and C–O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans
作者:Kashmiri Neog、Ashwini Borah、Pranjal Gogoi
DOI:10.1021/acs.joc.6b01966
日期:2016.12.2
A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C–H bondactivation/C–O and C–Cbond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology