Rhodium-Catalyzed Asymmetric Hydrogenation of 3-Benzoylaminocoumarins for the Synthesis of Chiral 3-Amino Dihydrocoumarins
An asymmetric hydrogenation of 3-benzoylaminocoumarins was achieved for the first time using our BridgePhos-Rh catalytic system, providing chiral 3-amino dihydrocoumarins in high yields (up to 98 %) and with excellent enantioselectivities (up to 99.7 % ee). The relationship between the enantioselectivities of the hydrogenations and the dihedral angles and the resulting π-π stacking effects of the BridgePhos-Rh complexes, which were determined by X-ray diffraction analysis, are discussed. The corresponding hydrogenated products allow for many transformations, providing several chiral skeletons with important physiological and pharmacological activities.
A one-pot [Bmim]OH-mediated synthesis of 3-benzamidocoumarins
The first example of an ionic liquid-promoted one-pot synthesis of 3-benzamidocoumarins from salicylaldehydes and 2-pheny-1,3-oxazolan-5-one via Knoevenagel condensation-ring transformation cascades has been reported. No by-product formation, operational
Yadav, Lal Dhar S.,Singh, Santosh,Rai, Vijai K.
experimental part
p. 2208 - 2212
(2009/08/07)
An efficient and facile synthesis of substituted 3-aminocoumarins under mw irradiation in dry media
A variety of 3-aminocoumarins were prepared by reaction of salicylaldehyde derivatives with benzoylglycine catalyzed by piperidine under microwave irradiation (MWI) and subsequent acid hydrolysis. The structure of products was proven by elemental analysis, IR, NMR and Mass spectra. These investigations will contribute to development of environmentally friendly and inexpensive processes in organic synthesis.
Valizadeh, Hassan,Shockravi, Abbas
p. 475 - 478
(2007/10/03)
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