A new regioselective Heck vinylation with enamides. Synthesis and investigation of fluorous-tagged bidentate ligands for fast separation |
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Authors: | Vallin Karl S A Zhang Qisheng Larhed Mats Curran Dennis P Hallberg Anders |
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Affiliation: | Department of Organic Pharmaceutical Chemistry, Uppsala University, BMC, Box-574, SE-751 23 Uppsala, Sweden. |
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Abstract: | Internal ligand-controlled Heck vinylations of enamides were performed with high regioselectivity and delivered moderate to good yields of dienamides. Controlled heating by microwave irradiation accelerated the palladium-catalyzed reactions, and full conversions were achieved after reaction times of only 15-30 min. New bidentate fluorous-tagged 1,3-bis(diphenylphosphino)propane ligands (F-dppp's) were synthesized and examined. The cationic vinylations of the enamides with F-dppp ligands rendered essentially the same alpha-selectivity and catalytic activity as in those vinylations where nonfluorous ligands were employed. After reaction, the fluorous-tagged ligand material was easily removed by convenient solid fluorous phase separation. The high selectivity, simplicity, and generality of the experimental procedure should make this approach to 2-acylamino-1,3-butadienes attractive. |
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