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Kim, Woo Gyum,Kang, Mi Eun,Lee, Jae Bin,Jeon, Min Ho,Lee, Sungmin,Lee, Jungha,Choi, Bongseo,Cal, Pedro M. S. D.,Kang, Sebyung,Kee, Jung-Min,Bernardes, Gonç,alo J. L.,Rohde, Jan-Uwe,Choe, Wonyoun American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.35
<P>Transition-metal-catalyzed or metal-free azide alkyne cycloadditions are methods to access 1,4 or 1,5-disubstituted 1,2,3-triazoles. Although the copper catalyzed cycloaddition to access 1,4-disubstituted products has been applied to biomolecular reaction systems, the azide alkyne cycloaddition to access the complementary 1,5-regioisomers under aqueous and ambient conditions remains a challenge due to limited substrate scope or moisture-/air-sensitive catalysts. Herein, we report a method to access 1,5-disubstituted 1,2,3-triazoles using a Cp2Ni/Xantphos catalytic system. The reaction proceeds both in water and organic solvents at room temperature. This protocol is simple and scalable with a broad substrate scope including both aliphatic and aromatic substrates. Moreover, triazoles attached with carbohydrates or amino acids are prepared via this cycloaddition.</P>
Toward Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity
Hu, Pan,Lee, Sangsu,Herng, Tun Seng,Aratani, Naoki,Gonç,alves, Thex301,o P.,Qi, Qingbiao,Shi, Xueliang,Yamada, Hiroko,Huang, Kuo-Wei,Ding, Jun,Kim, Dongho,Wu, Jishan American Chemical Society 2016 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.138 No.3
<P>Open-shell singlet diradicaloids display unique electronic, nonlinear optical, and magnetic activity and could become novel molecular materials for organic electronics, photonics, and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this Article, we report our efforts toward a tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties, and chemical reactivity were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introduction of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/antiaromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.</P>
Hu, Pan,Lee, Sangsu,Park, Kyu Hyung,Das, Soumyajit,Herng, Tun Seng,Gonç,alves, Thex301,o P.,Huang, Kuo-Wei,Ding, Jun,Kim, Dongho,Wu, Jishan American Chemical Society 2016 Journal of organic chemistry Vol.81 No.7
<P>The fundamental relationship between structure and diradical character is important for the development of open-shell diradicaloid-based materials. In this work, we synthesized two structural isomers bearing a 2,6-naphthoquinodimethane or a 1,5-naphthoquinodimethane bridge and demonstrated that their diradical characters and chemical reactivity are quite different. The mesityl-or pentafluorophenyl-substituted octazethrene derivatives <B>OZ-M/OZ-F</B> and their isomer <B>OZI-M</B> (with mesityl substituents) were synthesized via an intramolecular Friedel–Crafts alkylation followed by oxidative dehydrogenation strategy from the key building blocks <B>4</B> and <B>11</B>. Our detailed experimental and theoretical studies showed that both isomers have an open-shell singlet ground state with a remarkable diradical character (<I>y</I><SUB>0</SUB> = 0.35 and 0.34 for <B>OZ-M</B> and <B>OZ-F</B>, and <I>y</I><SUB>0</SUB> = 0.58 for <B>OZI-M</B>). Compounds <B>OZ-M</B> and <B>OZ-F</B> have good stability in an ambient environment, while <B>OZI-M</B> has high reactivity and can be easily oxidized to a dioxo product <B>15</B>, which can be correlated to their different diradical characters. Additionally, we investigated the physical properties of <B>OZ-M</B>, <B>OZ-F</B>, and <B>15</B>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2016/joceah.2016.81.issue-7/acs.joc.6b00172/production/images/medium/jo-2016-00172x_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo6b00172'>ACS Electronic Supporting Info</A></P>