Dual catalyst-controlled
intramolecular unactivated C(sp3)-H amination and oxygenation
of carbamates merging visible-light
photocatalysis and earth-abundant transition metal catalysis have
been reported. Useful amino alcohol and diol derivatives could be
selectively obtained from readily available tertiary alcohol derivatives.
The possible mechanisms have been proposed via a 1,5-HAT process followed
by Lewis acid-controlled cyclization. The nickel and zinc catalysts
inhibit the formation of oxygenation and amination products, respectively.
An interesting phenomenon of chirality transfer is also observed.
Over the last decade, N–N bond formation as a synthetic strategy has emerged as a powerful key step in the construction of highly valuable heterocycles from easily obtained materials. This review focuses on recent methods used to build N–N bonds, classified by intra- and intermolecular reactions with various types of N–X (O, C, N, H) bond cleavage.1 I ntroduction2 Intramolecular N–N Bond Formation2.1 Cleavage of N–O Bonds2.2 Cleavage of N–C Bonds2.3 Cleavage of N–N Bonds2.4 Cleavage of N–H Bonds2.4.1 Construction of Pyrazole Derivatives2.4.2 Construction of Triazole Derivatives2.4.3 Construction of Indazole and Pyrazoline Derivatives2.4.4 Construction of Other N–N Bond Derivatives3 Intermolecular N–N Bond Formation4 Conclusion
The visible-light-promoted diastereodivergent intramolecular oxyamination of alkenes is described to construct oxazolindinones, pyrrolidinones and imidazolidones via mild generation of primary amidyl radicals from functionalized hydroxylamines. A unique phenomenon of highly diastereoselective ring-opening of aziridines controlled by electron sacrifices was observed. Highly diastereoselective amino alcohols derivatives were obtained efficiently through this protocol in gram scales. The mechanistic studies suggested the isolatable anti-aziridine intermediates were generated quickly from primary amidyl radicals and the diastereoselectivities were controlled by pK values of the electron sacrifices.
Most of data set can be represented in an asymmetric matrix. How to mine the uncertain information from the matrix is the primary task of data processing. As a typical unsupervised learning method, three-way k-means clustering algorithm uses core region and fringe region to represent clusters, which can effectively deal with the problem of inaccurate decision-making caused by inaccurate information or insufficient data. However, same with k-means algorithm, three-way k-means also has the problems that the clustering results are dependent on the random selection of clustering centers and easy to fall into the problem of local optimization. In order to solve this problem, this paper presents an improved three-way k-means algorithm by integrating ant colony algorithm and three-way k-means. Through using the random probability selection strategy and the positive and negative feedback mechanism of pheromone in ant colony algorithm, the sensitivity of the three k-means clustering algorithms to the initial clustering center is optimized through continuous updating iterations, so as to avoid the clustering results easily falling into local optimization. Dynamically adjust the weights of the core domain and the boundary domain to avoid the influence of artificially set parameters on the clustering results. The experiments on UCI data sets show that the proposed algorithm can improve the performances of three-way k-means clustering results and is effective in revealing cluster structures.
An efficient method for the synthesis of isoquinolinone derivatives via photopromoted carboamination of alkynes is developed. Starting from the readily available propargyl alcohol derivatives, the polycyclic isoquinolinone derivatives could be...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.