1,721,049 research outputs found
Cravotto HECK REACTION WITH VERY LOW LIGANDLESS CATALYST LOAD ACCELERATED BY MICROWAVES OR SIMULTANEOUS MICROWAVES/ULTRASOUND IRRADIATION
No full textStructural determination of coumarin derivatives. Diels-Alder adducts using 3-methylene-2,4-chromanedione as trapping agent
No full textWith a series of unsatured compounds, 3-methylene-2,4-chromanedione can behave as ambident heterodiene or as dienophile affording the hetero-Diels-Alder and Diels-Alder adducts, respectively. The structural analysis aimed at identifying the peculiar spectral parameters of these adducts, has been performed via multidimensional NMR experiments supported by Molecular Mechanics calculations
Epoxidation studies on lathyra-6(17), 12-dienes. Revised structure of the Euphorbia factor L1
No full textThe Chemistry of Coumarin Derivatives .6. Diels-alder Trapping of 3-methylene-2,4-chromandione - A New Entry To Substituted Pyrano[3,2-c]coumarins
No full text3-Methylene-2,4-chromandione (1) can be generated from dicumarol or from paraformaldehyde and 4-hydroxycoumarin. 1 is a versatile substrate for cycloaddition reactions. Depending on the reaction partner, 1 can behave as an ambident heterodiene or as a dienophile. The reaction was investigated with a series of olefins and dienes, including several isoprenoids. Some generalizations could be drawn and rationalized in terms of HOMO-LUMO interactions. The reaction of 1 and certain asymmetrically substituted olefins gives pyrano[3,2-c]coumarins in a highly regio- and chemoselective way. As an application of this reaction to natural products chemistry, a concise (three steps) synthesis of the prenylated coumarin (+/-)-isoferprenin (35a) is reported
4-HYDROXYCOUMARIN AND RELATED SYSTEMS: SITOSELECTIVITY OF THE MITSUNOBU REACTION WITH PRENYL ALCOHOLS
No full textA straightforward entry into enantiomerically enriched beta-amino-alpha-hydroxyphosphonic acid derivatives
No full textThe asymmetric aminohydroxylation (AA) reaction of beta-substituted vinylphosphonates under Sharpless protocol followed by hydrolysis afforded beta-amino-alpha-hydroxyphosphonic acids in moderate to good ee. (C) 1998 Elsevier Science Ltd. All rights reserved
- …
