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Search for "umpolung reactions" in Full Text gives 6 result(s) in Beilstein Journal of Organic Chemistry.
Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field
Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179
- a nucleophilic reacting center. In addition to umpolung reactions with electrophiles, Breslow intermediates can undergo oxidation with the formation of radical cations or electrophilic acylazolium cations. The acylazolium cation in turn can undergo nucleophilic attack resulting in C–O and C–N
First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell
Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98
- used as organocatalyst in two classical umpolung reactions of cinnamaldehyde: its cyclodimerization and its oxidative esterification. Keywords: Breslow intermediate; cathodic reduction; flow electrochemistry; N-heterocyclic carbene; oxidative esterification; Introduction Ionic liquids (ILs) are well
Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines
Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34
- products, besides relying on performed control experiments, we also refer to the underdeveloped umpolung reactions of imines, considering, in particular, the copper-catalyzed process reported quite recently by Zhang, Hou and co-workers [29]. In our case, we presume the possible reaction mechanism shown in
Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions
Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32
- efforts began by examining reactions where the substrate to be oxidized underwent the electron-transfer reaction directly at the electrode surface. We have employed reactions of this nature to functionalize amides [13][14] and to conduct umpolung reactions [15][16] that originate from electron-rich
N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters
Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169
- -amino-β-keto esters; cross-aza-benzoin; α-imino ester; N-heterocyclic carbenes; organocatalysis; umpolung reactions; Introduction α-Amino-β-keto ester derivatives are one of the fundamental structural subunits in natural products such as miuraenamides [1], and important building blocks for the
- including C–C bond construction, that is, formal addition of acyl anion equivalents generated from aldehydes 1 with NHCs, to α-imino esters 2 (Figure 1, (f)). Although a large number of NHC-catalyzed umpolung reactions, such as the benzoin reaction and Stetter reaction, have been developed [24][25][26][27
N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis
Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43
- encouraged many chemists to search intensively for new NHC ligands, and this has led to the establishment of a very fruitful research area in organic chemistry [4][5][6][7][8][9][10]. A particularly interesting application comprises the use of “umpolung” reactions [11] (inversion of polarity) catalyzed by N
- ” reactions of aldehydes started as long ago as 1832, and the preparation of sterically hindered triazolium salts in 1996 provided a solid basis for highly stereoselective “umpolung” reactions utilizing NHCs [12]. In addition, conjugate “umpolung” relates to a process in which α,β-unsaturated aldehydes 3 are
- -heterocyclic carbenes, such as the benzoin condensation and the Stetter reaction. In these reactions, the NHC effects an “umpolung” of the normal carbonyl reactivity, and the electrophilic aldehyde carbon atom thus becomes nucleophilic and can attack a variety of electrophiles. The story of “umpolung
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