Maki Minakawa

Enantioselective Allylic Amination of Trifluoromethyl Group Substituted Racemic and Unsymmetrical 1,3-Disubstituted Allylic Esters by Palladium Catalysts

The palladium-catalyzed regio- and enantioselective allylic amination of trifluoromethyl group substituted racemic and unsymmetrical 1,3-disubstituted allylic esters has been accomplished. The enantioselective formation of the α-type allylic amines was attained by the dynamic kinetic asymmetric transformation (DYKAT).

Direct dehydrative esterification of alcohols and carboxylic acids with a macroporous polymeric acid catalyst.

A macroporous polymeric acid catalyst was prepared for the direct esterification of carboxylic acids and alcohols that proceeded at 50-80 °C without removal of water to give the corresponding esters with high yield. Flow esterification for the synthesis of biodiesel fuel was also achieved by using a column-packed macroporous acid catalyst under mild conditions without removal of water.

Ruthenium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1-Arylallyl Esters

The regio- and enantioselective allylic amination of racemic monosubstituted allylic esters, such as 1-arylallyl acetates, with cyclic secondary amines has been accomplished. The RuCl3/(S,S)-ip-pybox catalyst system has effectively catalyzed the reaction to afford the enantiomerically enriched branch-type allylic amines with perfect regioselectivity and high enantioselectivity.

Copper-Catalyzed Intermolecular Hydroamination of Internal Alkynes with Anilines and Amines

The copper-catalyzed regioselective intermolecular hydroamination of the aryl and trifluoromethyl group or electron-withdrawing group substituted internal alkynes with amines has been accomplished. The reaction was effectively catalyzed by the ligand-free Cu(OTf)2 and afforded the intended amine derivatives in good yields after treatment of NaBH3CN.

Iron-catalyzed [2 + 2 + 2] cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes

Iron-catalyzed [2 + 2 + 2] intermolecular cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes afforded the corresponding trifluoromethyl group substituted benzene derivatives in high yield with excellent selectivity.

In-Water and Neat Batch and Continuous-Flow Direct Esterification and Transesterification by a Porous Polymeric Acid Catalyst

A porous phenolsulphonic acid—formaldehyde resin (PAFR) was developed. The heterogeneous catalyst PAFR was applied to the esterification of carboxylic acids and alcohols, affording the carboxylic acid esters in a yield of up to 95% where water was not removed from the reaction mixture. Surprisingly, the esterification in water as a solvent proceeded to afford the desired esters in high yield. PAFR provided the corresponding esters in higher yield than other homogeneous and heterogeneous catalysts. The transesterification of alcohols and esters was also investigated by using PAFR, giving the corresponding esters. PAFR was applied to the batch-wise and continuous-flow production of biodiesel fuel FAME. The PAFR-packed flow reactor that was developed for the synthesis of carboxylic acids and FAME worked for four days without loss of its catalytic activity.

Driving an equilibrium acetalization to completion in the presence of water

Formation of an acetal from a carbonyl substrate by condensation with an alcohol is a classical reversible equilibrium reaction in which the water formed must be removed to drive the reaction to completion. A new method has been developed for acetalization of carbonyl substrates by diols in the presence of water. Complexation of poly(4-styrenesulfonic acid) with poly(4-vinylpyridine) generates a catalytic membrane of polymeric acid at the interface between two parallel laminar flows in a microchannel of a microflow reactor. The catalytic membrane provides a permeable barrier between the organic layer and water-containing layer in the reaction, and permits discharge of water to the outlet of the microreactor to complete the acetalization. Condensation of a variety of carbonyl substrates with diols proceeded in the presence of water in the microflow device to give the corresponding acetals in yields of up to 97% for residence times of 19 to 38 s.

Dual Pd and CuFe2O4 Nanoparticles in a Core/Shell Silica Microsphere

Significance: A dual catalyst containing Pd and CuFe2O4 nanoparticles in a core/shell silica microsphere (SiO2@CuFe2O4-Pd) for selective hydrogenation of arylacetylenes to styrenes was described. A sequential modification of SiO2 with CuFe2O4 and Pd nanoparticles led to the formation of the dual catalyst SiO2@CuFe2O4-Pd. The hydrogenation of arylacetylenes was performed in hexane under H2 (1 atm) using SiO2@CuFe2O4-Pd to give the corresponding styrenes in 98–99% conversion with 73–98% selectivity. Comment: SiO2@CuFe2O4-Pd was prepared on the basis of the authors’ previous work (Chem. Mater. 2008, 20, 6738). The SiO2@CuFe2O4-Pd catalyst was recovered by using an external magnet and reused in the hydrogenation of phenylacetylene (1st use: 98% conversion, 98% selectivity; 2nd use: 99% conversion, 98% selectivity; 3rd use: 98% conversion, 97% selectivity). SiO2@CuFe2O4-Pd was characterized by powder X-ray diffraction, TEM, EDX, HR-SEM, ICP, fielddependent magnetization, etc. 1) Cu(NO3)2⋅2.5H2O, Fe(NO3)3⋅9H2O, Igepal CO-520, EtOH/n-octyl ether 363–573 K then dried at 353 K 2) annealed at 773 K SiO2 SiO2@CuFe2O4 SiO2@CuFe2O4-Pd : CuFe2O4 : Pd