Mesoporous monolithic hybrid cellulose-2.5-acetate (CA)/polymer supports were prepared under solvent-induced phase separation conditions using cellulose-2.5-acetate microbeads 8-14 μm in diameter, 1,1,1-tris(hydroxymethyl)propane and 4,4'-methylenebis(phenylisocyanate) as monomers as well as THF and n-heptane as porogenic solvents. 4-(Dimethylamino)pyridine and dibutyltin dilaurate (DBTDL), respectively, were used as catalysts. Monolithic hybrid supports were used in transesterification reactions of vinyl butyrate with 1-butanol under continuous, supported ionic liquid-liquid conditions with Candida antarctica lipase B (CALB) and octylmethylimidazolium tetrafluoroborate ([OMIM(+) ][BF4 (-) ]) immobilized within the CA beads inside the polymeric monolithic framework and methyl tert-butyl ether (MTBE) as the continuous phase. The new hybrid bioreactors were successfully used in dimensions up to 2×30 cm (V=94 mL). Under continuous biphasic liquid-liquid conditions a constant conversion up to 96 % was achieved over a period of 18 days, resulting in a productivity of 58 μmol mg(-1) (CALB) min(-1) . This translates into an unprecedented turnover number (TON) of 3.9×10(7) within two weeks, which is much higher than the one obtained under standard biphasic conditions using [OMIM(+) ][BF4 (-) ]/MTBE (TON=2.7×10(6) ). The continuous liquid-liquid setup based on a hybrid reactor presented here is strongly believed to be applicable to many other enzyme-catalyzed reactions.
Tropane‐derived phosphorus–olefin hybrid ligands bearing various combinations of P‐units (chiral BINOL‐derived units/achiral PPh2‐units) with a tropene skeleton (chiral/achiral) have been synthesized and used in Cu‐catalysed conjugate 1,4‐additions of diethylzinc to cyclic enones and in Rh‐catalysed 1,4‐additions of phenylboronic acid (Hayashi–Miyaura reaction) with cyclic and acyclic enones. Whereas in Cu‐catalysed reactions only moderate yields and ee values (up to 49 % ee) were obtained, up to 97 % ee was observed in the Hayashi–Miyaura reaction with various substrates. The most promising results in both reactions were achieved with ligands 11 and 15, which contain a chiral alkene/achiral P‐unit or an achiral alkene/chiral P moiety, respectively, and where the metal is complexed on the exo side of the tropene skeleton. In contrast, ligands with an endo coordination mode showed only low (13) or no activity (12) in all of the 1,4‐additions. NMR and ESI‐MS experiments revealed the presence of two cationic [RhI(15)2]+ species in solution.
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