Efficient one pot and chemoselective synthesis of functionalized 3-bromo-4,5-dihydroisoxazole derivatives via 1,3-dipolar cycloaddition reactions of nitrile oxides
A novel, metal-free and chemoselective approach for the synthesis of 4,5-dihydroisoxazole derivatives has been developed by the reaction of readily accessible starting materials including 4-oxo-4H-chromene-3-carbaldehyde, 1-phenyl-2-(1,1,1-triphenyl-λ5-phosphanylidene)ethan-1-one and dibromoformaldoxime under mild conditions in the presence of KHCO3.
Asymmetric Michaelreaction of 3-homoacyl coumarins and chromone-fused dienes was developed by employing a chiral squaramide, and a series of coumarin chromone skeletons were furnished in moderate to high yields (up to 99%) and stereoselectivities (up to 98 : 2 dr, 99% ee).
Synthesis and structure elucidation of novel pyrazolyl-2-pyrazolines obtained by the reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with phenylhydrazine
作者:Clementina M. M. Santos、Artur M. S. Silva、József Jekőc、Albert Lévai
DOI:10.3998/ark.5550190.0013.522
日期:——
Novel 3-aryl-5-4-[5-(2-hydroxyphenyl)-1-phenylpyrazolyl]}-2-pyrazolines 2a-g have been prepared by the treatment of 3-(3-aryl-3-oxopropenyl)chromen-4-ones 1a-g with phenylhydrazine in refluxing acetic acid. NMR studies on deuteriochloroform solutions of pyrazolyl-2-pyrazolines 2a-g at different temperatures showed that at room temperature a mixture of diastereomers are present. This diastereoselectivity