Hydrogen peroxide based oxidation of hydrazines using HBr catalyst
作者:Jian Wang、Zichao Ma、Wanting Du、Liming Shao
DOI:10.1016/j.tet.2021.132546
日期:2021.12
Azo compounds (RN = NR′) are an important class of organic molecules that find wide application in organic synthesis. Herein, we report an efficient, practical and metal-free oxidation of hydrazines (RNH-NHR’) to azo compounds using 5 mol% HBr and hydrogen peroxide as terminal oxidant. This new method has been demonstrated by 40 examples with excellent yields. In addition, we showcased two examples
Carbene‐Catalyzed Enantioselective Aromatic N‐Nucleophilic Addition of Heteroarenes to Ketones
作者:Yonggui Liu、Guoyong Luo、Xing Yang、Shichun Jiang、Wei Xue、Yonggui Robin Chi、Zhichao Jin
DOI:10.1002/anie.201912160
日期:2020.1.2
and optical purities. Our reaction involves the formation of an unprecedented aza-fulvene-type acylazolium intermediate. A broad range of N-heteroaromatic aldehydes and electron-deficient ketone substrates works effectively in this transformation. Several of the chiral N,O-acetal products afforded through this protocol exhibit excellent antibacterial activities against Ralstonia solanacearum (Rs) and
Highly Enantioselective Intermolecular Stetter Reaction of Simple Acrylates: Synthesis of α-Chiral γ-Ketoesters
作者:Nathalie E. Wurz、Constantin G. Daniliuc、Frank Glorius
DOI:10.1002/chem.201202432
日期:2012.12.14
Simple Stetter: A novel N‐heterocyclic carbene (NHC) was designed by combining an electron‐rich 2,6‐dimethoxy substituent and an underestimated yet promising chiral motif. With this NHC in hand, a highlyenantioselectiveintermolecularStetterreaction of simple acrylates was developed, yielding versatile α‐chiral γ‐ketoesters. This represents the first catalytic asymmetric route towards these valuable
Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes
作者:Chieh-Hung Tien、Matt R. Adams、Michael J. Ferguson、Erin R. Johnson、Alexander W. H. Speed
DOI:10.1021/acs.orglett.7b02695
日期:2017.10.20
shown to catalyze the 1,2 hydroboration of 19 imines, and three α,β unsaturated aldehydes with pinacolborane, including examples that did not undergo hydroboration by previously reported diazaphospholene systems. DFT calculations support a mechanism where a triazaphospholene cation interacts with the substrate, a mechanism distinct from diazaphospholene catalyzed hydroborations.
1,4-Bis-Dipp/Mes-1,2,4-Triazolylidenes: Carbene Catalysts That Efficiently Overcome Steric Hindrance in the Redox Esterification of α- and β-Substituted α,β-Enals
作者:Veera Reddy Yatham、Wacharee Harnying、Darius Kootz、Jörg-M. Neudörfl、Nils E. Schlörer、Albrecht Berkessel
DOI:10.1021/jacs.5b11796
日期:2016.3.2
2,4-triazolium salts were synthesized and evaluated as (pre)catalysts in the redox esterification of various α- or β-substituted enals. In particular the 1,4-bis-Mes/Dipp-1,2,4-triazolylidenes overcome the above limitations and efficiently catalyze the redox esterification of a whole series of α/β-substituted enals hitherto not amenable to NHC-catalyzed transformations. The synthetic value of 1,4-bis-Mes/Dipp-1