title: A new regioselective Heck vinylation with enamides. Synthesis and investigation of fluorous-tagged bidentate ligands for fast separation.
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.
authors.affiliation: Department of Organic Pharmaceutical Chemistry, Uppsala University, BMC, Box-574, SE-751 23 Uppsala, Sweden.
authors.forename: Karl S A
authors.initials: KS
authors.lastname: Vallin
authors.forename: Qisheng
authors.initials: Q
authors.lastname: Zhang
authors.forename: Mats
authors.initials: M
authors.lastname: Larhed
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Curran
authors.forename: Anders
authors.initials: A
authors.lastname: Hallberg