A low pressure microflow system was developed for palladium-catalyzed multiphase carbonylation reactions in an ionic liquid. The microflow system resulted in superior selectivity and higher yields in carbonylative Sonogashira coupling and amidation reactions of aryl iodides compared to the conventional batch system.
Theoretical investigations were performed
for typical iridium complexes,
Ir(C∧N)3, Ir(C∧N)2(C’∧N’), Ir(C∧N)2(N ∧O) and Ir(C∧N)2(O∧O), at the MCSCF+SOCI+SOC//B3LYP/SBKJC+p
level of theory. For Ir(dfppy)2(pic) (so-called FIrpic) and its related complexes, the introduction
of a fluoride into ppy ligands provides a blue shift
of about 20 nm for emission spectra, while the replacement of a pic ligand by an acac ligand does not seriously
affect the emission spectra of these complexes. It is proposed that
the homo-cis,hetero-O-cis isomer
(HC-5f, see text) of FIrpic should be used as a brighter
blue-color material instead of the homo-N-trans isomer
(HNT-5f). The energy difference between these isomers
is less than 1 kcal/mol, and the energy barrier of the isomerization
between these isomers is calculated to be larger than 30 kcal/mol.
It was also found that the use of two ancillary ligands, such as Ir(C∧N)(N ∧O)2 and Ir(C∧N)(O∧O)2, is unfortunately
inappropriate to energetically lift the π* orbital.
A photochemical [2+2] cycloaddition reaction was executed in a microflow system using glass-made microchannels having 1000-μm width and 500-μm depth. The reaction of cyclohexenones with vinyl acetates in a microflow system under irradiation (300 W, Hg lamp) gave [2+2] cycloaddition products in good yield with a residence time of 2 h, which is a remarkably shortened reaction time compared with a batch system using the same light source.
Tributyltin hydride-mediated radical reactions of organic halides were successfully carried out in a continuous flow system using a microreactor. The reactions proceeded within a very short period of time, coupled with quickly decomposing radical initiators such as V-65 and V-70. The continuous flow reaction system was applied to gram scale synthesis of a key intermediate for furofuran lignans.
SummaryRadical-based carbonylation reactions of alkyl halides were conducted in a microflow reactor under pressurized carbon monoxide gas. Good to excellent yields of carbonylated products were obtained via radical formylation, carbonylative cyclization and three-component coupling reactions, using tributyltin hydride or TTMSS as a radical mediator.
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