- Rh(iii)-catalyzed, hydrazine-directed C-H functionalization with 1-alkynylcyclobutanols: A new strategy for 1: H -indazoles
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Rh(iii)-catalyzed coupling of phenylhydrazines with 1-alkynylcyclobutanols was realized through a hydrazine-directed C-H functionalization pathway. This [4+1] annulation, based on the cleavage of a Csp-Csp triple bond in alkynylcyclobutanol, provides a new pathway to prepare diverse 1H-indazoles under mild reaction conditions. This journal is
- Zhang, Lei,Chen, Junyu,Chen, Xiahe,Zheng, Xiangyun,Zhou, Jian,Zhong, Tianshuo,Chen, Zhiwei,Yang, Yun-Fang,Jiang, Xinpeng,She, Yuan-Bin,Yu, Chuanming
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p. 7415 - 7418
(2020/07/15)
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- A Versatile, Traceless C-H Activation-Based Approach for the Synthesis of Heterocycles
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A versatile, traceless C-H activation-based approach for the synthesis of diversified heterocycles is reported. Rh(III)-catalyzed, N-amino-directed C-H alkenylation generates either olefination products or indoles (in situ annulation) in an atom- and step-economic manner at room temperature. The remarkable reactivity endowed by this directing group enables scale-up of the reaction to a 10 g scale at a very low catalyst loading (0.01 mol %/0.1 mol %). Ex situ annulation of olefination product provides entry into an array of heterocycles.
- Zhou, Shuguang,Wang, Jinhu,Zhang, Feifei,Song, Chao,Zhu, Jin
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supporting information
p. 2427 - 2430
(2016/06/09)
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- Ruthenium(II)-Catalyzed Traceless C?H Functionalization Using an N?N Bond as an Internal Oxidant
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A previously elusive RuII-catalyzed N?N bond-based traceless C?H functionalization strategy is reported. An N-amino (i.e., hydrazine) group is used for the directed C?H functionalization with either an alkyne or an alkene, affording an indole derivative or olefination product. The synthesis features a broad substrate scope, superior atom and step economy, as well as mild reaction conditions.
- Zhou, Shuguang,Wang, Jinhu,Chen, Pei,Chen, Kehao,Zhu, Jin
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supporting information
p. 14508 - 14512
(2016/10/03)
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- Simple synthesis of racemic pyrrolo[2,3-b]indoles: Formal total synthesis of (±)-physostigmine
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Racemic pyrrolo [2,3-b]indoles were efficiently synthesized by the reaction of aromatic hydrazines with 4-chloro-2-methylbutanal. A formal total synthesis of physostigmine was achieved.
- Tsuji, Riichiro,Nakagawa, Masako,Nishida, Atsushi
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p. 587 - 593
(2007/10/03)
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- Structures of reactive nitrenium ions: Time-resolved infrared laser flash photolysis and computational studies of substituted N-methyl-N-arylnitrenium ions
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A series of para-substituted N-methyl-N-phenylnitrenium ions (N-(4-biphenylyl)-N-methylnitrenium ion, N-(4-chlorophenyl)-N-methylnitrenium ion, N-(4-methoxyphenyl)-N-methylnitrenium ion, and N-(4-methylphenyl)-N-methylnitrenium ion) were generated through photolysis of the appropriately substituted 1-aminopyridinium salt. Laser flash photolysis using UV - vis detection as well as photoproduct analysis verified that the expected nitrenium ions were formed cleanly and rapidly following photolysis. Laser flash photolysis with time-resolved infrared detection allowed for structural characterization of the nitrenium ions through observation of a symmetrical aromatic C=C stretch in the region 1580-1628 cm-1. The specific frequencies reflect the degree of quinoidal character present in each phenylnitrenium ion (i.e., the degree to which the nitrenium ion resembles a 4-iminocyclohexa-2,5-dienyl cation). The 4-methoxy derivative shows the highest frequency C=C stretch, indicating that this strongly π-electron-donating substituent imparts more quinoidal character, and the 4-chloro derivative shows the lowest frequency C=C stretch, suggesting that it possesses the least quinoidal character. Quantum calculations using density functional theory (BPW91/cc-pVDZ) were carried out on the same nitrenium ions. The theoretically derived IR frequencies showed excellent quantitative agreement with the experiment. The computed structures show significant bond length alternation in the phenyl rings, shortened C-N bond lengths, and substantial positive charge delocalization into the phenyl rings. All of these effects are more pronounced with increasing π-donating character of the ring substituent. Arylnitrenium ions are well described as 4-iminocyclohexa-2,5-dienyl cations.
- Srivastava, Sanjay,Ruane, Patrick H.,Toscano, John P.,Sullivan, Michael B.,Cramer, Christopher J.,Chiapperino, Dominic,Reed, Elizabeth C.,Falvey, Daniel E.
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p. 8271 - 8278
(2007/10/03)
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- SIMPLE PREPARATION OF N-ALKYL-N-ARYLHYDRAZINES FROM DIAZOTABLE N-ARYLAMINES
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Phase-Transfer-catalyzed N-alkylation of arylhydrazones 2, followed by hydrazinolysis with hydrazine hydrate in the presence of concentrated hydrochloric acid, provides a new access to N-alkyl-N-arylhydrazines 3.
- Gonzalez, Asensio
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p. 1225 - 1230
(2007/10/02)
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