Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation

• Olga C. Dennehy,
• Valérie M. Y. Cacheux,
• Benjamin J. Deadman,
• Denis Lynch,
• Stuart G. Collins,
• Humphrey A. Moynihan and
• Anita R. Maguire

Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246

• opportunity for aerobic oxidation of the thiophenolate anion to diphenyl disulfide, while sodium metal is no longer used as part of the process. α-Thio-β-chloroacrylamide cascade in flow Successful conversion of the β-chloroacrylamide cascade step from batch to flow posed a number of challenges. The reaction

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• Scheme 5). More recently, the method was extended to the mild copper-catalyzed aerobic oxidation of hydroxylamines [48][49][50]. In 2014, the Lykakis group reported the selective oxidation of various arylamines into the corresponding nitrosoarenes through polyoxometalate anions supported on mesoporous

• oxidation in the presence of catalytic amounts of Cu(II) and pyridine [48][49][50] were used for the preparation of acylnitroso compounds. In 2015, the Whiting group reported an extensive study of acylnitroso compounds prepared in situ by the catalytic aerobic oxidation of hydroxycarbamate using CuCl2 and 2

• reactions of acylnitroso compounds in [4 + 2] cycloadditions indicate several facts. The copper–oxazoline complex behaves as an excellent catalyst for the aerobic oxidation of acylhydroxamic acids. However, this system is useful only for hydroxamic acids containing a heteroatom between the aryl and carbonyl

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• Liu and Bi [24]. This useful transformation makes use of CuI/O2 in DMSO to convert methyl ketones into aldehydes in a sustainable manner. Recently our group reported a synthetic protocol for the copper- and iron-catalyzed aerobic oxidation of the methylene group of aryl(di)azinylmethanes using acetic

• was used to quantify the monodeuterated species. Benzylic oxygenation of benzoannulated azines and diazines (5). Classical (top) and new formal (bottom) synthesis of Mefloquine. Iron-catalyzed aerobic oxidation of papaverine (15). Iron-catalyzed aerobic oxidation of phenyl-substituted 4

• -benzylpyridines (1).a Iron and copper-catalyzed aerobic oxidation of pyridine-substituted 2-benzylpyridines (3).a The influence of the purification method on the amount of Fe impurities in papaveraldine (15) after oxidation. An extended solvent screening for the base metal-catalyzed aerobic oxidation reaction.a

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• dihalogenated products 31 (Scheme 13). A preliminary mechanistic analysis suggested that the bromination and chlorination reactions proceeded via different pathways. According the color change in the reaction vessel, the formation of molecular bromine was hypothesized via aerobic oxidation, which suggested the

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”

• Julio Benites,
• Juan Meléndez,
• Cynthia Estela,
• David Ríos,
• Luis Espinoza,
• Iván Brito and
• Jaime A. Valderrama

Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255

• sensitized solar-induced photooxygenation of 1,5-DHN (1), might undergo in situ phenylamination followed by aerobic oxidation to give the expected target aminojuglone 4a and/or 4b. In order to evaluate the reactions involved in this hypothetical strategy, the solar photosensitized photooxygenation of 1,5-DHN

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• enhanced by mild dielectric heating. Furthermore, it is a versatile green procedure which generally enables the isolation of esters to be carried out by simple filtration in almost quantitative yields. Keywords: aerobic oxidation; alcohol; esterification; heterogeneous catalysis; microwaves; Introduction

• developed for the aerobic oxidation of primary and secondary alcohols to aldehydes and ketones using Au [4][5][6][7][8], Pd [9][10][11][12], Ru [13][14][15][16] and Cu [17][18][19] supported catalysts. An elegant approach to the direct oxidative esterification of alcohols has been described in recent years

• not require co-catalysts, co-oxidants or ligands. Results and Discussion Pd-catalyzed esterification can be performed with Pd(II) species [31][32][33][34][35][44]. The challenge of performing aerobic oxidation under MW irradiation in a preliminary investigation prompted us to select benzylalcohol and

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• Abstract Since the beginning of the century, N-hydroxyphthalimide and related compounds have been revealed to be efficient organocatalysts for free-radical processes and have found ample application in promoting the aerobic oxidation of a wide range of organic substrates. When combined with different co

• initiators. Azo-initiators were mainly employed for the synthesis of phenol derivatives by aerobic oxidation of isopropyl aromatics. For example, the oxidation of 2,6-diisopropylnaphthalene with air in the presence of α,α’-azobisisobutyronitrile (AIBN) and NHPI, followed by decomposition with sulfuric acid

• system could promote the nitric aerobic oxidation of alkylbenzenes under NHPI-catalysis, leading to the selective formation of benzyl alcohols through the corresponding acetates, if operating in acetic acid solution (Scheme 10) [26]. According to the proposed mechanism, being that the concentrations of

NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

• Lennart Möhlmann,
• Stefan Ludwig and
• Siegfried Blechert

Beilstein J. Org. Chem. 2013, 9, 602–607, doi:10.3762/bjoc.9.65

• of aldehydes to the corresponding acids or esters. The reaction proceeds under metal-free conditions by using N-heterocyclic carbenes as organocatalysts in combination with environmentally friendly oxygen as the terminal oxidation agent. Keywords: aerobic oxidation; chemoselective oxidation; metal

• -free oxidation; N-heterocyclic carbene; organocatalysis; Introduction The development of efficient and selective aerobic oxidation methods for organic substrates is of increasing interest and an attractive goal in green chemistry [1][2][3]. In a recent communication we reported on selective oxidation

• further systematic studies that have not previously been done, to gain more information about the substrate scope and especially the selectivity of this NHC-catalysed aerobic oxidation. The results are summarized in Figure 2. To our delight, various aldehydes, including aliphatic (Figure 2, entries 2–4

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

• Aurélie Dos Santos,
• Laurent El Kaim,
• Laurence Grimaud and
• Caroline Ronsseray

Beilstein J. Org. Chem. 2011, 7, 1310–1314, doi:10.3762/bjoc.7.153

• Pyrazolidinones were prepared in a two-step sequence starting from α-hydrazonocarboxylic acids. After a four-component Ugi coupling, the resulting hydrazone was engaged in a copper triggered [3 + 2] cycloaddition/aerobic oxidation cascade. Keywords: aerobic oxidation; copper(II); [3 + 2] cycloaddition; hydrazone

• pyrazolidinone under oxidative conditions from simple hydrazone derivatives (Scheme 1) [13]. The cascade features a [3 + 2] cycloaddition coupled with an aerobic oxidation of the resulting pyrazolidine. A further oxidative coupling may be observed according to the substitution pattern of the starting acyl

CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

• Shuxu Gao,
• Yu Liu and
• Shengming Ma

Beilstein J. Org. Chem. 2011, 7, 396–403, doi:10.3762/bjoc.7.51

• oxidation [17][24] or Dess–Martin oxidation [16][17][24][25][28][31][32][33]: Catalytic aerobic oxidation has not so far been reported. Due to the synthetic potential of 1,2-allenyl ketones, it is desirable to develop an aerobic oxidation protocol for 2,3-allenols. In this paper we wish to report the CuCl

• -catalyzed aerobic oxidation of 2,3-allenols by applying a mixed ligand approach using copper as the catalyst [12][13]. Results and Discussion After screening the Pd- [6][7][8][9][10] and Ru-catalyzed [14][15] protocols without success, we began a study of the oxidation of 2-hexyl-1-phenylbuta-2,3-diene-1-ol

• 73% conversion of 1l within 10 hours. Conclusion In conclusion, we have developed a method for the aerobic oxidation of 2,3-allenols, which uses molecular oxygen in air or pure oxygen as the oxidant. In this reaction, CuCl with a 1:1 ratio of 1,10-phenanthroline and bipyridine was used as the

Synthesis of 3-(phenylazo)-1,2,4-triazoles by a nucleophilic reaction of primary amines with 5-chloro- 2,3-diphenyltetrazolium salt via mesoionic 2,3-diphenyltetrazolium- 5-aminides

• Shuki Araki,
• Satoshi Hirose,
• Yoshikazu Konishi,
• Masatoshi Nogura and
• Tsunehisa Hirashita

Beilstein J. Org. Chem. 2009, 5, No. 8, doi:10.3762/bjoc.5.8

• , aerobic oxidation of 5b in ethanol gave triazole 3b in 69% yield, though the reaction took 10 d (Scheme 4). On the basis of these experimental results, the most plausible reaction mechanism is illustrated in Scheme 5. Nucleophilic substitution of the chlorine atom of 2 by amine gives 5-aminotetrazolium