The aromatic C(sp
)-H functionalization of unprotected naphthols with
-phenyl-
-diazoesters under mild conditions catalyzed by CuCl and CuCl
exhibits high efficiency and unique
-selectivity. In this ...study, the combination of density functional theory (DFT) calculations and experiments is employed to investigate the mechanism of C-H functionalization, which reveals the fundamental origin of the site-selectivity. It explains that CuCl-catalyzed
-selective C-H functionlization is due to the bimetallic carbene, which differs from the reaction catalyzed by CuCl
via monometallic carbene. The results demonstrate the function of favourable H-bond interactions on the site- and chemo-selectivity of reaction through stabilizing the rate-determining transition states in proton (1,3)-migration.
A range of qinghaosu （artemisinin） analogues were synthesized from modified dihydroqinghao acid/aldehyde using dark singlet oxygen to trigger off the key step of the trioxane formation. The newly ...accessed 1,2,4-trioxanes featured a side chain extended from the carbon corresponding to the lactone carbonyl group of qinghaosu through a stable carbon-carbon single bond instead of an acetal oxygen-carbon bond in most similar analogues in the literature Biotin and various amines were also connected to the qinghaosu core, respectively, through such a linear tether in efforts to develop hybrids and potentially useful probes in search of the in vivo targets.
The aromatic C(spsup.2)-H functionalization of unprotected naphthols with α-phenyl-α-diazoesters under mild conditions catalyzed by CuCl and CuClsub.2 exhibits high efficiency and unique ...ortho-selectivity. In this study, the combination of density functional theory (DFT) calculations and experiments is employed to investigate the mechanism of C-H functionalization, which reveals the fundamental origin of the site-selectivity. It explains that CuCl-catalyzed ortho-selective C-H functionlization is due to the bimetallic carbene, which differs from the reaction catalyzed by CuClsub.2 via monometallic carbene. The results demonstrate the function of favourable H-bond interactions on the site- and chemo-selectivity of reaction through stabilizing the rate-determining transition states in proton (1,3)-migration.
In order to solve the problem of starting a surface mounted permanent synchronous magnet motor(SPMSM) with unknown initial position, this paper proposed a method for locating the initial position ...based on discrete Fourier transform feature extraction and polarity identification of forward and reverse pulse excitation. Based on the traditional high frequency voltage injection method of pulse vibration, this paper studied a new method of location feature extraction. The discrete Fourier transform is used to replace the filter to simplify the algorithm structure, and at the same time, this can also avoid amplitude attenuation and phase shift caused by filtering. In addition, for the polarity compensation of the estimated position, this paper designed a forward and reverse pulse excitation method with multi-position check and DC bias compensation, which overcomes the common problem that the current peak discrimination is easily affected by the bias voltage. The proposed method does not depend on the convex polarity of the motor structure, and effectively solves the problem that the surface mounted permanent synchronous magnet is difficult to locate the initial position. Finally, a prototype platform is built for experimental analysis. The results show that the proposed method can detect the initial position of the motor quickly and accurately in the static state, had has strong practicability and robustness.
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