Divergent Construction of Diverse Scaffolds through Catalyst-Controlled C-H Activation Cascades of Quinazolinones and Cyclopropenones.

A transition-metal-catalyzed C-H activation cascade strategy to rapidly construct diverse quinazolinone derivatives in a one-pot manner is reported. The catalysts play an important role in the different transformations. Additionally, the procedure is scalable, proceeds with high efficiency and good chemo-/regio-selectivity, and tolerates a range of functional groups.

fastESN: Fast Echo State Network.

Echo state networks (ESNs) are reservoir computing-based recurrent neural networks widely used in pattern analysis and machine intelligence applications. In order to achieve high accuracy with large model capacity, ESNs usually contain a large-sized internal layer (reservoir), making the evaluation process too slow for some applications. In this work, we speed up the evaluation of ESN by building a reduced network called the fast ESN (fastESN) and achieve an ESN evaluation complexity independent of the original ESN size for the first time. FastESN is generated using three techniques. First, the high-dimensional state of the original ESN is approximated by a low-dimensional state through proper orthogonal decomposition (POD)-based projection. Second, the activation function evaluation number is reduced through the discrete empirical interpolation method (DEIM). Third, we show the directly generated fastESN has instability problems and provide a stabilization scheme as a solution. Through experiments on four popular benchmarks, we show that fastESN is able to accelerate the sparse storage-based ESN evaluation with a high parameter compression ratio and a fast evaluation speed.

Microbial denitrification characteristics of typical decentralized wastewater treatment processes based on 16S rRNA sequencing.

Despite the widespread application of decentralized wastewater treatment (WWT) facilities in China, relatively few research has used the multi-media biological filter (MMBF) facilities to investigate the microorganism characteristics. This study utilizes 16S rRNA high-throughput sequencing (HTS) technology to examine the microbial biodiversity of a representative wastewater treatment (WWT) system in an expressway service area. The pathways of nitrogen removal along the treatment route were analyzed in conjunction with water quality monitoring. The distribution and composition of microbial flora in the samples were examined, and the dominant flora were identified using LEfSe analysis. The FAPROTAX methodology was employed to investigate the relative abundance of genes associated with the nitrogen cycle and to discern the presence of functional genes involved in nitrogen metabolism. On average, the method has a high level of efficiency in removing COD, TN, NH3-N, and TP from the effluent. The analysis of the microbial community identified a total of 40 phyla, 111 classes, 143 orders, 263 families, and 419 genera. The phyla that were predominantly observed include Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Nitrospirae, Bacteroidetes. The results show that the system has achieved high performance in nitrogen removal, the abundance of nitrification genes is significantly higher than that of other nitrogen cycle genes such as denitrification, and there are six nitrogen metabolism pathways, primarily nitrification, among which Nitrospirae and Nitrospira are the core differentiated flora that can adapt to low temperature conditions and participate in nitrification, and are the dominant nitrogen removal flora in cold regions. This work aims to comprehensively investigate the diversity and functional properties of the bacterial community in decentralized WWT processes.

Three-Component Couplings among Heteroarenes, Difluorocyclopropenes, and Water via C-H Activation.

Three-component couplings have been realized for efficiently constructing various nitrogen-containing skeletons via C-H activation, where difluorocyclopropenes have been first identified as coupling partners. Many substrates including sp2 and sp3 C-H substrates were well tolerated, furnishing the corresponding products in good yields. Furthermore, a catalyst-dependent reaction was also developed, enabling divergent construction of two different frameworks. The application value of these reactions was demonstrated in gram-scale experiments with as little as 1 mol % catalyst.

Rh(III)-Catalyzed C-H Olefination Cascades to Divergently Construct Diverse Polyheterocycles by Tuning Manipulations of Directing Groups.

Inspired by the diversity created by nature, organic chemists have been using a divergent strategy to improve the synthetic efficiency of diverse molecules. Transition-metal-catalyzed C-H functionalization has become one of the most straightforward, powerful, and atom-economical methods to construct complex scaffolds. However, C-H activation initiated divergent transformation to prepare diverse molecules is still limited. To address this challenge, we herein developed Rh(III)-catalyzed C-H olefination/annulation reaction cascades to divergently construct diverse polyheterocycles by tuning manipulations of directing groups (DGs). Up to 9 distinct scaffolds were creatively synthesized under simple conditions with good functional group tolerance, chemo-, and regioselectivity. Such a versatile strategy and its extension may encourage researchers to discover more promising manipulations of DGs for transition-metal-catalyzed C-H bond activation, making diverse available targets and materials that would have been previously out of range.

Divergent C-H activation synthesis of chalcones, quinolones and indoles.

We here report a condition-controlled divergent synthesis strategy of chalcones, quinolones and indoles, which was achieved via a C-H activation reaction of N-nitrosoanilines and cyclopropenones. Variations of Ag salts are observed to be crucial for divergently constructing the three distinct chemical scaffolds. A Rh(i)- and Rh(iii)-cocatalyzed decarbonylation/C-H activation/[3+2] annulation cascade reaction was developed for the synthesis of indoles. These methodologies are characterized by mild reaction conditions, high functional group tolerance, and amenability to gram-scale synthesis, providing a reference for future derivation of new chemical scaffolds by C-H activation.

[Formation of W/O microemulsions in TBP-Pd(II)-HCl extraction system and spectroscopic research on the evolution of solution aggregation structure].

The formation of W/O microemulsions in the extraction system TBP-Pd(II)-HCl was investigated. The solution structural evolution of the palladium loaded organic phases, with the variation in the content of acid into the organic phases, was characterized by various spectroscopic techniques such as DLS, FTIR and 31P-/1H NMR. The results indicated that (1) the extraction behaviors of palladium was related to the formation of W/O microemulsion structure in the loaded organic solutions. Because of the co-extraction of hydrochloric acid, there formed the microscopic aggregates in the loaded organic phases. (2) The variation in the HCl content in organic phase resulted in corresponding changes in solution structure. With the increase in the HCl content, the average radii of nanoscopic aggregates in the organic phases increased and then decreased. The extraction of HCl into the organic phase exhibited a distinct impact on the O-H stretching vibration and O-H-O bending vibration of water molecules in the microscopic W/O micelles. FTIR spectra of the organic phase saturated with acids show that the broad band of O-H stretching vibration of water extended to a very wide range and overlaped with the C-H stretching vibration bands. The higher the acid concentration in the organic phase was, the greater the overlapping. On the other hand, it was also observed that a remarkable change appeared in the O-H-O bending vibration of water and the stretching vibration of P=O in TBP molecules shifted to lower frequency. With the increase in acid content in the TBP organic phases, the observed 31P NMR chemical shifts decreased and varied to up-field; whereas the 1H NMR chemical shift of H+ increased and even became larger than that of deuterium chloride-d at a lower frequency field. The changes in delta 31P to opposite direction of delta H+ means that TBP molecules were associated with acid protons and water molecules in microemulsion pools to form RP=O x H+ or RP=O x H3O+, and then interacted with PdCl4(2-) complex ions, which finally led to the extraction of palladium into the organic phase. (3) When forming the W/O reversed micelles/microemulsions, the concentration of acid within the microscopic micelles was even higher than that of saturated concentrated hydrochloric acid. It was the microscopic structural changes in organic phase microemulsion "water pool" that resulted in the corresponding variations in the palladium extraction behaviors.