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2. Heterogeneous Rhodium Single-Atom-Site Catalyst Enables Chemoselective Carbene N–H Bond Insertion

Author

Chen, Yuanjun, Zhang, Ruixue, Chen, Zhiwen, Liao, Jiangwen, Song, Xuedong, Liang, Xiao, Wang, Yu, Dong, Juncai, Singh, Chandra Veer, Wang, Dingsheng, Li, Yadong, Toste, F Dean, and Zhao, Jie

Subjects
Inorganic Chemistry, Chemical Sciences, Organic Chemistry, Physical Chemistry, General Chemistry, Chemical sciences, Engineering
Abstract

Transition-metal-catalyzed carbene insertion reactions of a nitrogen-hydrogen bond have emerged as robust and versatile methods for the construction of C-N bonds. While significant progress of homogeneous catalytic metal carbene N-H insertions has been achieved, the control of chemoselectivity in the field remains challenging due to the high electrophilicity of the metal carbene intermediates. Herein, we present an efficient strategy for the synthesis of a rhodium single-atom-site catalyst (Rh-SA) that incorporates a Rh atom surrounded by three nitrogen atoms and one phosphorus atom doped in a carbon support. This Rh-SA catalyst, with a catalyst loading of only 0.15 mol %, exhibited exceptional catalytic performance for heterogeneous carbene insertion with various anilines and heteroaryl amines in combination with diazo esters. Importantly, the heterogeneous catalyst selectively transformed aniline derivatives bearing multiple nucleophilic moieties into single N-H insertion isomers, while the popular homogeneous Rh2(OAc)4 catalyst produced a mixture of overfunctionalized side products. Additionally, similar selectivities for N-H bond insertion with a set of stereoelectronically diverse diazo esters were obtained, highlighting the general applicability of this heterogeneous catalysis approach. On the basis of density functional theory calculations, the observed selectivity of the Rh-SA catalyst was attributed to the insertion barriers and the accelerated proton transfer assisted by the phosphorus atom in the support. Overall, this investigation of heterogeneous metal-catalyzed carbene insertion underscores the potential of single-atom-site catalysis as a powerful and complementary tool in organic synthesis.

Published
2024

3. Identification of a novel LFNG variant in a Chinese fetus with spondylocostal dysostosis and a systematic review

Author

Wang, Lin, Mizumoto, Shuji, Zhang, Ruixue, Zhang, Yuqi, Liu, Yuan, Cheng, Wenjing, Li, Xin, Dan, Min, Zhang, Chunyan, Gao, Xinru, Wang, Juan, Han, Jiaqi, Jiao, Lianying, Wang, Yating, Jin, Qiujie, Yang, Lihui, Li, Chenxing, Li, Shuxian, Zhu, Jinhui, Jiang, Hai, Nishimura, Gen, Yamada, Takahiro, Yamada, Shuhei, Cai, Na, Qiang, Rong, and Guo, Long

Published
2024
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4. On the colorability of bi-hypergraphs

Author

Zhang, Meiqiao, Dong, Fengming, and Zhang, Ruixue

Subjects
Mathematics - Combinatorics, O5C15, 05C65
Abstract

A {\it mixed hypergraph} ${\cal H}=({\cal V},{\cal C},{\cal D})$ consists of the vertex set ${\cal V}$ and two families of subsets of $2^{{\cal V}}$: the family ${\cal C}$ of co-edges and the family ${\cal D}$ of edges. ${\cal H}$ is said to be colorable if there is a mapping $f$ from ${\cal V}$ to the set of positive integers such that $|\{f(v):v\in e\}|<|e|$ for each $e\in {\cal C}$ and $|\{f(v):v\in e\}|>1$ for each $e\in {\cal D}$. There exist mixed hypergraphs which are uncolorable, and quite little about these mixed hypergraphs is known. A mixed hypergraph is called a bi-hypergraph if its co-edge set and edge set are the same. In this article, we first apply Lov\'asz local lemma to show that any $r$-uniform bi-hypergraph with $r\ge 4$ is colorable if every edge is incident to less than $(r-1)^{r-1}e^{-1}-1$ other edges, where $e$ is the base of natural logarithms. Then, we show that among all the uncolorable $3$-uniform bi-hypergraphs, the smallest size of a minimal one is ten, which answers a question raised by Tuza and Voloshin in 2000. As an extension, we provide a minimal uncolorable $3$-uniform bi-hypergraph of order $n$ and size at most $\frac{7n}3-4$ for every $n\ge 6$., Comment: 19 pages, 4 figures

Published
2023

8. Complete characterization of s-bridge graphs with local antimagic chromatic number 2

Author

Lau, Gee-Choon, Shiu, Wai-Chee, Zhang, Ruixue, Premalatha, K., and Nalliah, M.

Subjects
Mathematics - Combinatorics, 05C78, 05C69
Abstract

An edge labeling of a connected graph $G = (V, E)$ is said to be local antimagic if it is a bijection $f:E \to\{1,\ldots ,|E|\}$ such that for any pair of adjacent vertices $x$ and $y$, $f^+(x)\not= f^+(y)$, where the induced vertex label $f^+(x)= \sum f(e)$, with $e$ ranging over all the edges incident to $x$. The local antimagic chromatic number of $G$, denoted by $\chi_{la}(G)$, is the minimum number of distinct induced vertex labels over all local antimagic labelings of $G$. In this paper, we characterize $s$-bridge graphs with local antimagic chromatic number 2.

Published
2022

10. A note on local antimagic chromatic number of lexicographic product graphs

Author

Lau, Gee-Choon, Shiu, Wai-Chee, Premalatha, K., Zhang, Ruixue, and Nalliah, M.

Subjects
Mathematics - Combinatorics
Abstract

Let $G = (V,E)$ be a connected simple graph. A bijection $f: E \rightarrow \{1,2,\ldots,|E|\}$ is called a local antimagic labeling of $G$ if $f^+(u) \neq f^+(v)$ holds for any two adjacent vertices $u$ and $v$, where $f^+(u) = \sum_{e\in E(u)} f(e)$ and $E(u$) is the set of edges incident to $u$. A graph $G$ is called local antimagic if $G$ admits at least a local antimagic labeling. The local antimagic chromatic number, denoted $\chi_{la}(G)$, is the minimum number of induced colors taken over local antimagic labelings of $G$. Let $G$ and $H$ be two disjoint graphs. The graph $G[H]$ is obtained by the lexicographic product of $G$ and $H$. In this paper, we obtain sufficient conditions for $\chi_{la}(G[H])\leq \chi_{la}(G)\chi_{la}(H)$. Consequently, we give examples of $G$ and $H$ such that $\chi_{la}(G[H]) = \chi(G)\chi(H)$, where $\chi(G)$ is the chromatic number of $G$. We conjecture that (i) there are infinitely many graphs $G$ and $H$ such that $\chi_{la}(G[H])=\chi_{la}(G)\chi_{la}(H) = \chi(G)\chi(H)$, and (ii) for $k\ge 1$, $\chi_{la}(G[H]) = \chi(G)\chi(H)$ if and only if $\chi(G)\chi(H) = 2\chi(H) + \lceil\frac{\chi(H)}{k}\rceil$, where $2k+1$ is the length of a shortest odd cycle in $G$.

Published
2022

29. Incorporating Self-attention Mechanism and Multi-task Learning into Scene Text Detection

Author

Ding, Ning, Peng, Liangrui, Liu, Changsong, Zhang, Yuqi, Zhang, Ruixue, Li, Jie, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Karlinsky, Leonid, editor, Michaeli, Tomer, editor, and Nishino, Ko, editor

Published
2023
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