The first rhodium‐catalyzed highly chemo‐, regio‐ and enantioselective hydroformylation of cyclopropyl‐functionalized trisubstituted alkenes affording useful chiral cyclopropyl entities is reported. ...Compared to generally used diphosphine ligands for asymmetric catalysis, the modified hybrid phosphorus ligand, named (R,S)‐DTBM‐Yanphos, can convert a series of readily available cyclopropyl‐functionalized trisubstituted alkenes into high‐value chiral cyclopropyl‐functionalized aldehydes with high selectivities (81–98 % ee). Gram‐scale reactions (TON up to 1500) and follow‐up transformations to the corresponding alcohol, acid, esters and nitrile are also presented. Finally, a possible hydroformylation mechanism involving ring‐open‐hydroformylation pathways is proposed based on control and deuteroformylation reactions.
The first rhodium‐diphosphine‐catalyzed highly chemo‐, regio‐ and enantioselective hydroformylation of cyclopropyl‐functionalized trisubstituted alkenes to afford high‐value chiral cyclopropyl entities is reported. Insights into this transformation were established by control, deuteroformylation, and gram‐scale reactions (TON up to 1500). Versatile follow‐up transformations to the corresponding alcohol, acid, esters and nitrile were also demonstrated.
Reported is an iridium catalyst for ortho‐selective C−H borylation of challenging secondary aromatic amide substrates, and the regioselectivity is controlled by hydrogen‐bond interactions. The ...BAIPy‐Ir catalyst forms three hydrogen bonds with the substrate during the crucial activation step, and allows ortho‐C−H borylation with high selectivity. The catalyst displays unprecedented ortho selectivities for a wide variety of substrates that differ in electronic and steric properties, and the catalyst tolerates various functional groups. The regioselective C−H borylation catalyst is readily accessible and converts substrates on gram scale with high selectivity and conversion.
Organization is key: Direct ortho‐selective C−H borylation is extremely challenging. Reported here is the first example for direct ortho‐C−H borylation of valuable secondary aromatic amides, and it involves preorganization through hydrogen‐bond formation between the ligand and the amide group of the substrate. The new iridium catalyst is readily available and yields unprecedented regioselectivity for more than 26 substrates without the need for specific directing groups.
The atom‐ and step‐efficient synthesis of chiral fused tricyclic lactams from readily available ketoesters using cheap ammonium salts as the nitrogen source is reported. This ruthenium‐catalyzed ...system operates through an efficient tandem dynamic kinetic asymmetric reductive amination (ARA)/lactamization and produces chiral fused tricyclic lactams in high yields with excellent diastereo‐ and enantioselectivity (up to >99 % ee, >20 : 1 dr and 98 % yield). The robust method was also applied to the concise synthesis of key intermediates in the synthesis of rivastigmine analogues and chiral N‐heterocyclic carbene catalysts.
An efficient and economical one‐pot approach to chiral fused tricyclic lactams from readily available ketoesters was developed by using cheap ammonium salts as the nitrogen source through ruthenium‐catalyzed tandem dynamic kinetic asymmetric reductive amination/lactamization. This protocol provides highly efficient access to drug intermediates and organocatalysts containing chiral polycyclic N‐heterocycles.
The diagnosis of biliary atresia (BA) remains a clinical challenge because affected infants have signs, symptoms, and serum liver biochemistry that are also seen in those with other causes of ...neonatal cholestasis (non‐BA). However, an early diagnosis and prompt surgical treatment are required to improve clinical outcome. Recently, the relative abundance of serum matrix metalloproteinase‐7 (MMP‐7) was suggested to have discriminatory features for infants with BA. To test the hypothesis that elevated serum concentration of MMP‐7 is highly diagnostic for BA, we determined the normal serum concentration of MMP‐7 in healthy control infants, and then in 135 consecutive infants being evaluated for cholestasis. The median concentration for MMP‐7 was 2.86 ng/mL (interquartile range, IQR: 1.32‐5.32) in normal controls, 11.47 ng/mL (IQR: 8.54‐24.55) for non‐BA, and 121.1 ng/mL (IQR: 85.42‐224.4) for BA (P < 0.0001). The area under the curve of MMP‐7 for the diagnosis of BA was 0.9900 with a cutoff value of 52.85 ng/mL; the diagnostic sensitivity and specificity were 98.67% and 95.00%, respectively, with a negative predictive value of 98.28%. Conclusion: Serum MMP‐7 assay has high sensitivity and specificity to differentiate BA from other neonatal cholestasis, and may be a reliable biomarker for BA.
A rolling bearing is an essential component of a rotating mechanical transmission system. Its performance and quality directly affects the life and reliability of machinery. Bearings’ performance and ...reliability need high requirements because of a more complex and poor working conditions of bearings. A bearing with high reliability reduces equipment operation accidents and equipment maintenance costs and achieves condition-based maintenance. First in this paper, the development of technology of the main individual physical condition monitoring and fault diagnosis of rolling bearings are introduced, then the fault diagnosis technology of multi-sensors information fusion is introduced, and finally, the advantages, disadvantages, and trends developed in the future of the detection main individual physics technology and multi-sensors information fusion technology are summarized. This paper is expected to provide the necessary basis for the follow-up study of the fault diagnosis of rolling bearings and a foundational knowledge for researchers about rolling bearings.
A catalytic route is developed to synthesize bio‐renewable catechol from softwood‐derived lignin‐first monomers. This process concept consists of two steps: 1) O‐demethylation of 4‐n‐propylguaiacol ...(4‐PG) over acidic beta zeolites in hot pressurized liquid water delivering 4‐n‐propylcatechol (4‐PC); 2) gas‐phase C‐dealkylation of 4‐PC providing catechol and propylene over acidic ZSM‐5 zeolites in the presence of water. With large pore sized beta‐19 zeolite as catalyst, 4‐PC is formed with more than 93 % selectivity at nearly full conversion of 4‐PG. The acid‐catalyzed C‐dealkylation over ZSM‐5 zeolite with medium pore size gives a catechol yield of 75 %. Overall, around 70 % catechol yield is obtained from pure 4‐PG, or 56 % when starting from crude 4‐PG monomers obtained from softwood by lignin‐first RCF biorefinery. The selective cleavage of functional groups from biobased platform molecules through a green and sustainable process highlights the potential to shift feedstock from fossil oil to biomass, providing drop ins for the chemicals industry.
Pining for catechol: A catalytic route is developed to synthesize bio‐renewable catechol from pinewood‐derived lignin‐first monomers. The two‐step process consists of O‐demethylation of 4‐n‐propylguaiacol over acidic beta zeolites in hot pressurized liquid water, delivering 4‐n‐propylcatechol, and gas‐phase C‐dealkylation of 4‐propylcatechol providing catechol and propylene over acidic ZSM‐5 zeolites in the presence of water.
Pulsed discharge plasma and its application is one of the promising directions in civilian areas of pulsed power technology. In order to promote the research and development of the theory and ...application technology for pulsed discharge plasma, in this paper, recent progress on the mechanism of nanosecond-pulse gas discharge and the characteristics and applications of typical pulsed plasma at the Institute of Electrical Engineering, Chinese Academy of Sciences is reviewed. Firstly, progress on mechanism of nanosecond-pulse discharge based on runaway electrons and measurement technology of runaway electrons is introduced. Then, the characteristics of three typical discharges, including direct-driven pulsed discharge, pulsed dielectric barrier discharge and pulsed plasma jet, are reviewed. Furthermore, typical plasma applications of pulsed plasma on surface modification and methane conversion are presented.
The configurations, stabilities, electronic, and magnetic attributes of the first row transition metal (TM)-substituted TMC
6
N
7
clusters have been investigated at the PBE level. The results display ...that the first row TM atoms are inclined to replace the N atom which approaches the N atom out of the C–N rings except for Cu and Zn. As for the CuC
6
N
7
and ZnC
6
N
7
clusters, the N atom out of the C-N rings is inclined to be substituted. The ScC
6
N
7
(GS), TiC
6
N
7
(GS), VC
6
N
7
(GS), CoC
6
N
7
(GS), TiC
6
N
7
(a), and CoC
6
N
7
(a) clusters display more structurally stabilities than the pristine C
6
N
8
clusters. The ground-state 3
d
TMC
6
N
7
clusters exhibit more dynamic stabilities than the pristine C
6
N
8
clusters except for Zn. Partial of 4
s
orbital electrons of TM atoms is transferred to the neighbor C atoms. The V, Cr, Mn, and Fe atoms of the ground-state TMC
6
N
7
clusters display the opposite spin to Co and Ni atoms of the ground-state TMC
6
N
7
clusters.
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