Lewis acid-catalyzed redox-neutral amination of 2-(3-pyrroline-1-yl)benzaldehydes via intramolecular [1,5]-hydride shift/isomerization reaction

• Chun-Huan Jiang,
• Xiantao Lei,
• Le Zhen,
• Hong-Jin Du,
• Xiaoan Wen,
• Qing-Long Xu and
• Hongbin Sun

Beilstein J. Org. Chem. 2014, 10, 2892–2896, doi:10.3762/bjoc.10.306

• : catalysis; C–H activation; hydride-shift; Lewis acid; redox reaction; Introduction The direct and selective functionalization of the inactive C(sp3)–H bond constitute an economically attractive strategy for organic syntheses [1][2][3][4][5][6][7][8][9][10]. Until now, a number of transition metals can be

• -alkylpyrroles could be formed via a redox isomerization reaction (Scheme 1, reaction 1) [34][35][36]. Moreover, we recently realized a Lewis acid-catalyzed intramolecular redox reaction using an aldehyde group as the H-shift acceptor to afford (2-(1H-pyrrol-1-yl)phenyl)methanol (Scheme 1, reaction 2) [37]. As

• requirement that the iminium formation reaction should be faster than the aldehyde redox reaction. Results and Discussion In our initial investigation, aldehyde 1a and dibenzylamine (2a) were chosen as the model reaction substrates. In the presence of 10 mol % PhCOOH, the reaction of 1a with 2a in DCE at rt

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• calculated Gibbs free energy of the dye regeneration redox reaction. These slightly endergonic values (0.42 and 0.12 eV) support the low kred and kox rate constants used for computation. The measured electron transfer rate constants are in line with the ΔG, confirming the low reactivity of 3PS toward EDB

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• a solvent. The aim of the study was to measure the redox potentials of the SG1 and LiCl/solvent and to conclude if a redox reaction could happen between these species. The redox potentials of SG1 and LiCl (4.5 wt %) in DMF and MeOH were then determined by cyclic voltammetry with a platinum electrode

• redox reaction is the one involving the reduction of the in situ formed Cl2 to Cl− and the oxidation of the nitroxide to an oxoammonium ion. In conclusion, if Cl2 can be formed in the system, then the oxidation of the SG1 nitroxide is possible. However, this hypothesis is challenging to validate since

Rh(III)-catalyzed directed C–H bond amidation of ferrocenes with isocyanates

• Satoshi Takebayashi,
• Tsubasa Shizuno,
• Takashi Otani and
• Takanori Shibata

Beilstein J. Org. Chem. 2012, 8, 1844–1848, doi:10.3762/bjoc.8.212

• reaction setup and is required to prevent the redox reaction between AgBF4 and 1a [24]. However, the use of [RhCp*(MeCN)3](BF4)2 [17] resulted in lower yield likely due to the coordination of MeCN (Table 1, entry 6). The yield significantly increased when the combination of [RhCp*(OAc)2(H2O)] [25] and 2

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• organocatalytic asymmetric C–H activation reaction was disclosed by Kim and co-workers for the synthesis of chiral tetrahydroquinolines 14 (Scheme 10) [24]. ortho-(Dialkylamino)cinnamaldehydes were employed as the substrates for this aminocatalytic intramolecular redox reaction. The authors first demonstrated a

• . Mechanism for the indole-annulation cascade reaction. Synthesis of N-alkylpyrroles and δ-hydroxypyrroles. Synthesis of N-alkylindoles 9 and N-alkylindolines 10. Mechanistic study for the N-alkylpyrrole formation. Benzoic acid catalysed decarboxylative redox amination. Organocatalytic redox reaction of ortho

• -(dialkylamino)cinnamaldehydes. Mechanism for aminocatalytic redox reaction of ortho-(dialkylamino)cinnamaldehydes. Asymmetric synthesis of tetrahydroquinolines having gem-methyl ester groups. Asymmetric synthesis of tetrahydroquinolines from chiral substrates 18. Organocatalytic biaryl synthesis by Kwong, Lei

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• alternative procedure for the generation and subsequent cycloaddition of azomethine ylide intermediates under gold catalysis. Importantly, they demonstrated that the intramolecular attack of a nitrone oxygen to a tethered gold-activated alkyne leads, by means of an internal redox reaction, to an α-carbonyl

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• (Scheme 9). With the objective of preparing a diaminopyran, we attempted to substitute the bromide atom in compound 15 with the azido group. Surprisingly, instead of the desired α-azido ketone, the formation of nitrone 21 was observed, which apparently involves an unusual internal redox reaction (Scheme

• moiety of trans-5a leading to products 13–15. Bromination of bicyclic dihydropyran trans-5b affording 16. Synthesis of epoxypyran 18 by bromination of cis-5d. Oxidative cleavage of dihydropyran 19 to lactone 20. Transformation of α-bromoketone 15 into nitrone 21 by an internal redox reaction