Hyperbranched and linear conjugated polysiloles incorporating arylene ethynylene subunits (6 and 7) were synthesized by the Sonogashira reaction. The two polymers possess unusual phenomena of PL, with gradual addition of water in their THF solution, the intensity of PL firstly increased and then decreased, this may be due to the aggregate-enhanced emission (AEE) effect and aggregation-caused quenching (ACQ) effect. The polymers function as sensitive fluorescent chemosensors for the detection of explosives, such as picric acid (PA) and TNT. The quenching constants of 6 for PA and TNT were 4.7 Â 10 À2 ppm À1 and 4.6 Â 10 À3 ppm À1 , respectively. The quenching constants of 7 for PA and TNT were 8.6 Â 10 À2 ppm À1 and 6.5 Â 10 À3 ppm À1 respectively. The polymer 7 has more detective efficiency for PA and TNT than that of polymer 6, this may be due to the less steric hindrance.
A highly efficient cross-coupling of diarylborinic acids and anhydrides with aryl chlorides and bromides has been effected by using a palladium catalyst system co-supported by a strong σ-donor N-heterocyclic carbene (NHC), N,N'-bis(2,6-diisopropylphenyl) imidazol-2-ylidene, and a strong π-acceptor phosphite, triphenylphosphite, in tert-BuOH in the present of K(3)PO(4)·3H(2)O. Unsymmetrical biaryls with a variety of functional groups could be obtained in good to excellent yields using as low as 0.01, 0.2-0.5, and 1 mol % palladium loadings for aryl bromides and activated and deactivated aryl chlorides, respectively, under mild conditions. A ligand synergy between the σ-donor NHC and the π-acceptor phosphite in the Pd/NHC/P(OPh)(3) catalytic system has been proposed to be responsible for the high efficacy to arylchlorides in the cross-coupling. A scalable and economical process has therefore been developed for synthesis of Sartan biphenyl from the Pd/NHC/P(OPh)(3) catalyzed cross-coupling of di(4-methylphenyl)borinic acid with 2-chlorobenzonitrile.
A telescoped process has been developed for practical preparation of N,O-chelated four-coordinate diarylborinates via direct reaction of N,O-chelate ligands with a diarylborinate solution prepared by removal of magnesium via precipitation from a one-pot reaction of aryl bromides, magnesium, and tributylborate. Ten N,O-chelated diarylborinates of representative N,O-chelate ligands of 2-picolinic acid, quinolin-8-ol, N-dimethylglycine, and amino alcohols were readily obtained in good yields. The telescoped process not only minimizes chemical waste and circumvents tedious purification of diarylborinic acids but also eliminates handling of Grignard reagents and improves compatibility with acid-sensitive groups.
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