Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• compounds were hydrogenated, oxidized, and lactonized in a similar fashion, utilizing either the Jones reagent or manganese dioxide as the oxidizing agent [18]. Santhamma et al. developed another route for steroidal spiro-γ-lactones at C-17, from estran-17-one and androstane-17-one derivatives [19]. The

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• easily overoxidized to carboxylic acids. Over the past decades a variety of methods have been developed, utilizing toxic heavy metals such as pyridinium dichromate (PDC) [3][4][5] or manganese dioxide (Figure 1) [6][7]. Molecular oxygen [8] and peroxides [9][10] can also be used as inexpensive terminal

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• have reported a manganese dioxide-catalyzed radical azidation of enol acetates to afford the corresponding azidoketones using dioxygen as the oxidant (Scheme 1A) [14]. The adoption of electrosynthesis in green and sustainable redox transformations has been experiencing a dynamic renaissance [15][16][17

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• ][32]. Therefore, we also accomplished the synthesis of 2-fluoroalkylated indenone and indanone by simple reactions (Scheme 3). An allylic oxidation was carried out with 10 equiv of manganese dioxide in dichloromethane as the solvent at 0 °C for 30 minutes, leading to the corresponding 2

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

• Xianzhi Chai,
• Hai-Hao Han,
• Yi Zang,
• Jia Li,
• Xiao-Peng He,
• Junji Zhang and
• He Tian

Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230

• integrate these functions into one molecule. By taking advantages of both redox-active/high loading features of two-dimensional (2D) manganese dioxide (MnO2) and dynamic fluorescence photoswitching of photochromic sensors, we here design a hybrid photochromic MnO2 glycosheet (Glyco-DTE@MnO2) to achieve the

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• added at C-5 of 4-chloro- (9a) and 4-fluorobenzo[c][2,7]naphthyridine (9b) as well as the 4-carboxamide 9c to give 5-substituted-5,6-dihydro derivatives, which were readily aromatized with manganese dioxide [13]. Further functionalization was performed by Stille cross coupling of a 4-chloro intermediate

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• , entry 3). When other oxidants, such as selenium oxide and manganese dioxide, were used, even at reflux temperature, no reaction took place (Table 2, entries 4 and 5). Owing to the concern of heavy metal pollution from the metal oxidant, organic oxidants were tested. Fortunately, DDQ in dioxane could

One-pot synthesis of epoxides from benzyl alcohols and aldehydes

• Edwin Alfonzo,
• Jesse W. L. Mendoza and
• Aaron B. Beeler

Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205

• its original disclosure, particular in the area of asymmetric synthesis [22][23][24]. Other notable advancements include the expansion of its scope by using organic bases and a one-pot oxidation/epoxidation sequence of benzyl alcohols with manganese dioxide and an exogenous sulfonium salt [25][26

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• heating, ultrasonication and solvent-free conditions alleviated the drawbacks to a major extent [56][57][58][59][60][61]. One such useful strategy include manganese dioxide (MnO2)-mediated oxidative aromatization of 1,4-DHP 45 to afford substituted pyridine derivatives 46 under microwave conditions

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Integration of enabling methods for the automated flow preparation of piperazine-2-carboxamide

• Richard J. Ingham,
• Claudio Battilocchio,
• Joel M. Hawkins and
• Steven V. Ley

Beilstein J. Org. Chem. 2014, 10, 641–652, doi:10.3762/bjoc.10.56

• which demonstrated the hydration of broad classes of nitriles by passing aqueous–organic solutions through a packed bed of manganese dioxide [21], we have found that heteroaromatic nitriles possessing a β-heteroatom can also be hydrolysed using hydrous zirconia [22][23] in a similar fashion (Figure 3

• packed beds facilitates recycling of the catalyst, providing a further cost advantage. Interestingly, we have now found that no activation of the zirconia is needed (this is the same as for nitrile hydrations with manganese dioxide, but unlike the use of zirconia as a heterogeneous catalyst for Meerwein

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Hypervalent iodine/TEMPO-mediated oxidation in flow systems: a fast and efficient protocol for alcohol oxidation

• Nida Ambreen,
• Ravi Kumar and
• Thomas Wirth

Beilstein J. Org. Chem. 2013, 9, 1437–1442, doi:10.3762/bjoc.9.162

• ; Introduction Oxidation of alcohols to carbonyl compounds plays an important role in organic chemistry. The transformation is traditionally achieved by using chromium-based reagents such as the Collins reagent, activated manganese dioxide, or procedures known as the Swern [1], Pfitzner–Moffatt [2] or Parikh

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• mersicarpine (60), is another illustration [31]. The aromatisation process in this example was incomplete under the usual conditions and required further treatment with manganese dioxide. The possibility of associating the radical chemistry of xanthates with various ionic reactions represents another powerful

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• ), manganese dioxide (10× excess w/w, ~101 g) was added portionwise and the mixture was stirred for approximately 2 min. The mixture was filtered through a silica plug (eluted with dichloromethane) and the solvent removed under reduced pressure to afford B as a yellow solid (9.50 g, 90% from 1,3-dithiole-2

Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine

• Jessica Baiget,
• Sabin Llona-Minguez,
• Stuart Lang,
• Simon P. MacKay,
• Colin J. Suckling and
• Oliver B. Sutcliffe

Beilstein J. Org. Chem. 2011, 7, 1407–1411, doi:10.3762/bjoc.7.164

• analogues containing the carboline heterocyclic moiety. A manganese dioxide mediated one-pot method starting with an activated alcohol and consisting of alcohol oxidation, Pictet–Spengler cyclisation, and oxidative aromatisation, offers a convenient process that allows access to β-carbolines. This one-pot

• costs and in addition has the advantage that there is less waste associated with reactions of this nature and therefore less environmental impact. Taylor et al. [16][17][18][19] have shown manganese dioxide to be a robust reagent for carrying out oxidations on a wide range of activated alcohols. They

• glycolate (1) to manganese dioxide would result in the formation of aldehyde 2. This can then undergo a condensation process with tryptamine (3) allowing the generation of imine 4. This intermediate is set up appropriately to undergo a Pictet–Spengler cyclization reaction resulting in the formation of

Multicomponent reaction access to complex quinolines via oxidation of the Povarov adducts

• Esther Vicente-García,
• Rosario Ramón,
• Sara Preciado and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2011, 7, 980–987, doi:10.3762/bjoc.7.110

• tetrahydroquinolines obtained through the Povarov multicomponent reaction have been oxidized to the corresponding quinoline, giving access to a single product through a two-step sequence. Several oxidizing agents were studied and manganese dioxide proved to be the reagent of choice, affording higher yields, cleaner

• reactions and practical protocols. Keywords: manganese dioxide; multicomponent reactions; oxidation; Povarov; quinolines; tetrahydroquinolines; Introduction Heterocycles are ubiquitous scaffolds in pharmaceuticals, natural products and biologically active compounds. Quinoline systems in particular

• aromatic species. The literature contains scattered reports of the use of oxidants for this transformation: 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), ceric ammonium nitrate (CAN), nitrobenzene, elemental sulfur, palladium and manganese dioxide among others, all of them far from being ideally suited