Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• –Crafts reactions, rather than an oxocarbenium. Keywords: 1-aryltetralines; Friedel–Crafts reaction; Hock rearrangement; oxidative cleavage; tandem reactions; Introduction The Hock cleavage [1] consists in the acid-catalyzed rearrangement of organic hydroperoxides, leading to the oxidative cleavage of a

• C–C bond adjacent to the hydroperoxide group (Scheme 1a). The best-known application of this reaction is the cumene process, which allows the production of millions of tons of phenol each year [2]. The reaction has also been used in an industrial synthesis of artemisinin [3]. Allylic hydroperoxides

• ], in the presence of a nucleophilic species. Recently, we applied this idea to the rearrangement of 1-indanyl hydroperoxides into 2-substituted chromane derivatives, involving the nucleophilic allylation of the rearranged oxocarbenium intermediate (Scheme 1b) [12][13]. Furthermore, it is interesting to

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• addition to the electron-rich C=C bond [58] or proton loss followed by β-functionalization [59][60][61]. The iminium cation catalysis is used in the activation of electrophilic properties of enones for the nucleophilic epoxidation by hydroperoxides (Scheme 2B). N-Heterocyclic carbene (NHC) organocatalysis

• active oxidative agent. Asymmetric quaternary ammonium phase-transfer catalysts proved to be effective in the asymmetric nucleophilic epoxidation of electron-poor alkenes by hydroperoxides [70] and the asymmetric hydroxylation of enolizable carbonyl compounds employing O2 or H2O2 as terminal oxidants [71

• –H2O2 system the adducts of H2O2 and ketones (perhydrates) can also be active oxidative species [51]. Dioxiranes formed from ketones and hydroperoxides are electrophilic oxygen transferring agents used in epoxidation (including asymmetric variants) [131][132], CH-hydroxylation, and other oxidation

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• the synthesis of chemical reagents with an endoperoxide bridge have been reported [77][78]. The classical method for endoperoxide synthesis is through cycloadditions of dienes and alkenes, using singlet oxygen. Furthermore, cyclizations of hydroperoxides with pendant alkenes or alkynes have also been

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• epoxides are formed through oxidation reactions in vivo, that occur in protein processes dependent on vitamin K [96][97]. Dwyer and co-workers described a procedure using sugar-derived hydroperoxides for the synthesis of epoxides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base [98][99

• anomeric hydroperoxides (HPO) to obtain epoxides 40 with moderate ees (Scheme 11B) [100][101]. Bunge and co-workers used the enantiomerically pure dihydroperoxide 41 in the DBU-mediated epoxidation of menadione (10) for the enantioselective synthesis of epoxide 42 (92% yield and 45–66% ee) (Scheme 11C

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• alcohols 67 and aliphatic acids 173 (Scheme 37) [144]. Through a DCC-mediated dehydrogenative condensation with hydroperoxides, carboxylic acids could generate alkyl diacyl peroxides and peresters in situ. Decarboxylation followed by radical addition across the alkene 108 would generate a succeeding alkyl

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• alcohol side product was not labeled, suggesting that alcohols are formed by radical trapping by oxygen and the intermediate formation of hydroperoxides. Conversely, cations would have been trapped by water, resulting in the formation of labeled alcohols. Cyclic voltammetry experiments showed an

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• can be exploited to access O-radicals from different classes of substrates. In particular, N-alkoxypyridinium and alkyl hydroperoxides have been exploited as competent O-radical sources (Scheme 38). These substrates can be activated through SET reduction and energy transfer, respectively. The cleavage

• used as initators for the synthesis of highly functionalized benzo[b]phosphole oxides from arylphosphine oxide and alkynes [162]. Alkyl hydroperoxides can act as oxidants in photocatalytic cycles, furnishing the desired alkoxy radicals. Several organic dyes have been exploited in these processes

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• (Scheme 26) [61][67][68]. In this section, both reactions are presented and discussed. Singlet oxygen in pericyclic reactions Many important organic transformations can be performed by singlet oxygen including ene, [2 + 2] and [4 + 2] cycloaddition reactions for the formation of hydroperoxides, dioxetanes

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• orchestrated redox process, an alkoxyl radical-guided strategy for the site-selective fluorination of unactivated methylene and methine C–H bonds was published by Liu and co-workers in 2018 (Scheme 44) [91]. The fluorination of various primary, secondary, and tertiary hydroperoxides was achieved in moderate to

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• reactions performed with bifunctional guanidines. In addition, excellent results (97% ee) were reported in unprecedented domino reactions promoted by squaramides recently. Miscellaneous transformations, including additions of methanol, hydroperoxides and arylboronic acids, were also developed with high

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• enantioselectively delivered oxabicyclo[4.3.0]nonanes [17]; the Lautens and Lan groups have also contributed to the further development of this reaction [18][19]. The Rovis group employed cyclohexadienone hydroperoxides in a chiral phosphoric acid-catalyzed [1,2]/[1,4]-addition cascade [20]. The same group also

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• hydroperoxides, aryl hydroperoxides, ketone peroxides, dialkyl peroxides, diacyl peroxides, peroxy esters, peroxydicarbonates, peroxyacetals, and inorganic peroxides are the most important radical initiators that are widely used in industrial processes in the manufacture of polymers from unsaturated monomers [1

• Baeyer−Villiger oxidation and it is one of the methods for the synthesis of commercially important caprolactone from cyclohexanone with peracetic acid [55][56]. Autoxidation processes with formation of hydroperoxides and their subsequent free-radical transformations with generation of carbon- and oxygen

• search for new synthetic methods for peroxides starting from carbonyl compounds, hydrogen peroxide, and hydroperoxides [121][122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155][156][157

Photoinduced 1,2,3,4-tetrahydropyridine ring conversions

• Baiba Turovska,
• Henning Lund,
• Viesturs Lūsis,
• Anna Lielpētere,
• Edvards Liepiņš,
• Sergejs Beljakovs,
• Inguna Goba and
• Jānis Stradiņš

Beilstein J. Org. Chem. 2015, 11, 2166–2170, doi:10.3762/bjoc.11.234

• attention has been paid to organic aromatic or heterocyclic hydroperoxides, probably due to their low thermal stability and high reactivity. Stable organic hydroperoxides were isolated in the early 1950s as products of autoxidation as well as catalytic oxygenation of indoles and tetrahydrocarbazoles [3][4

• ][5][6]. In 1944 hydroperoxides were first obtained by H. Hock [7] and R. Udris [8][9][10] as the catalytic oxidation products of cumene. Heterocyclic hydroperoxides have been less represented, although some of these constitute the best choice for selective oxidations even in nature. When the peroxy

• functional group is placed near to electronegative groups, the oxidizing capability of hydroperoxides can be increased. This effect was particularly observed on heterocyclic systems. Results and Discussion Photosensitized aerobic oxidative aromatization [11][12][13][14] of Hantzsch 1,4-dihydropyridines has

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

• challenging chemical bond for direct activation. Consequently, the examples on copper-catalyzed halogenation of inactive C(sp3)–H bond remained barely explored. In 2010, Ball and Kundu [68] developed a protocol of remote C–H chlorination of alkyl hydroperoxides by means of copper catalysis. As displayed in

• Scheme 23, the alkyl hydroperoxides 69 and proper chlorine source (NH4Cl or iPr2NH·HCl) could couple each other in the presence of CuI and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDTA) to provide γ-chlorinated alcohols 70 via an intramolecular redox process. To enable the transformation, CuCl

• of bromoindolizines. Copper-mediated C–H halogenation of azacalix[1]arene[3]pyridines. Copper-mediated cascade synthesis of halogenated pyrrolones. Copper-mediated alkene C–H chlorination in spirothienooxindole. Copper-catalyzed remote C–H chlorination of alkyl hydroperoxides. Copper-catalyzed C–H

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• ) vs lit. [8] [α]D +42.0° (c 3.2, CHCl3)), obtained by treatment of 12 with TBAF in MeCN, resulted very bitter, as usually are the hydroperoxides (Table 3). Thus, the crude material of the photooxygenation was treated with an over stoichiometric amount of TMSCl (Scheme 3). In these conditions, after 24

Synthesis of the furo[2,3-b]chromene ring system of hyperaspindols A and B

• Danielle L. Paterson and
• David Barker

Beilstein J. Org. Chem. 2015, 11, 265–270, doi:10.3762/bjoc.11.29

• antibacterial and antiviral activities, as well as inhibitory activity on thromboxane A2 and leukotriene D4 [4]. Acylphloroglucinols are known to act as anti-oxidants, by reducing hydroperoxides and hydrogen peroxide, thereby suppressing the formation of the reactive species [9]. The hyperaspidinols 1 and 2

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

• . Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C–O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups

• acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less frequently. In the case of O-reagent PhI(O2CR)2, dehydrogenated carboxylic acid RCO2H is preliminary included in the oxidant, so C–H acyloxylation with PhI(O2CR)2 can be considered

• reagents. The formation of N-oxyl radicals 212 and 207 from oximes and N-hydroxyimides was confirmed by ESR spectroscopy [197][198]. The oxidative coupling of 1,3-dicarbonyl compounds [199] and their hetero analogues [200] 213 with tert-butyl hydroperoxides catalyzed by transition metal salts (Cu, Fe, Co

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

• Nathan J. Gesmundo and
• David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

• hydroperoxides with pendant alkenes or alkynes have been developed. Selected examples include Pd(II)-catalyzed hydroalkoxylation reactions of unsaturated hydroperoxides [9], Au(I)-catalyzed endoperoxidation of alkynes [10] and Brønsted acid-catalyzed enantioselective acetalization/oxa-Michael addition cascade

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• provides an efficient tool for introducing the hydroperoxide function. The reaction starts with the coordination of oxygen to the double bond followed by the formation of hydroperoxides presumably by a stepwise or concerted mechanism [229][230]. The oxidation of α,β-unsaturated ketones 1a–c by singlet

• acetic anhydride and pyridine at room temperature (Scheme 2). It should be emphasized that a mixture of dioxolanes 5 and 6 in a ratio of 7:3 is formed already in the first step [232]. The photooxygenation of oxazolidines 7a–d through the formation of hydroperoxides 8a–d gives spiro-fused oxazolidine

• peroxides 47 are formed as by-products, which are desilylated during hydrolysis to give the unsaturated hydroperoxides 50 (Scheme 16, Table 7) [249]. 1,2-Dioxolanes can be produced from oxetanes 53a,b containing a double bond in the side chain according to a similar scheme. The first step afforded

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• peroxide or hydroperoxides [11][12], intramolecular displacements of reversibly formed hemiacetals and allylic alcohols [8][13], displacement of resonance-activated alcohols with electron-poor nitrogen nucleophiles [14], and a synthesis of homoallylated amines from condensation of carbonyl groups with an

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

• was estimated at 88.1 kcal/mol [12]. This value is similar to the BDE of O–H in hydroperoxides, suggesting that the faster reactivity of PINO compared to peroxyl radicals should be attributed to an enhanced polar effect involved in the hydrogen abstraction by this nitroxyl radical [13]. Furthermore

• of the dihydroperoxide oxidation product, gave the corresponding 2,6-naphthalenediol in 92% yield (Scheme 3) [16]. As expected, the replacement of AIBN with a transition-metal complex (Co(OAc)2) resulted in a collapse of selectivity due to the redox decomposition of the hydroperoxides. This catalytic

• several commercially available azo-compounds (including AIBN and 2,2’-azobis(2,4-dimethylvaleronitrile) (AMVN)) as radical initiators at different temperatures for the NHPI-catalyzed oxidation of cyclohexylbenzene (CHB) to the corresponding hydroperoxides, finding a high selectivity in the oxygenation at

Copper-catalyzed aerobic aliphatic C–H oxygenation with hydroperoxides

• Pei Chui Too,
• Ya Lin Tnay and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2013, 9, 1217–1225, doi:10.3762/bjoc.9.138

• aerobic oxygenation of aliphatic C–H bonds with hydroperoxides, which proceeds by 1,5-H radical shift of putative oxygen-centered radicals (O-radicals) derived from hydroperoxides followed by trapping of the resulting carbon-centered radicals with molecular oxygen. Keywords: copper; 1,4-diols; free

• radical; 1,5-H radical shift; hydroperoxides; molecular oxygen; Introduction Aliphatic sp3 C–H bonds are ubiquitous components in organic molecules but rather inert towards most of the chemical reactions. It thus remains as one of the most challenging topics in organic synthesis to develop catalytic

• envision employing hydroperoxides as precursors for O-radicals in the presence of Cu salts. The lower valent Cu(I) species could potentially undergo single-electron reduction of hydroperoxides to produce the corresponding O-radicals [10][11][12][13]. Ball recently reported CuCl-catalyzed aliphatic C–H

Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations

• Ram Awatar Maurya,
• Chan Pil Park and
• Dong-Pyo Kim

Beilstein J. Org. Chem. 2011, 7, 1158–1163, doi:10.3762/bjoc.7.134

• illumination homogeniety of the microreactor also plays an important role. These factors make the triple-channel microreactor quite promising for photosensitized oxygenation reactions. The ratio of hydroperoxides 2 and 3 were found to be identical (1:1.5 as determined by 1 H NMR) in both the microreactor and

Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization

• Axel G. Griesbeck,
• Lars-Oliver Höinck and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2010, 6, No. 61, doi:10.3762/bjoc.6.61

• sensitization of triplet oxygen with meso-tetraphenylporphyrin (TPP) were performed in polystyrene beads under solvent-free conditions (Scheme 1) [18][19]. Numerous applications of the hydroperoxides 4 and 7, that result from the singlet oxygen ene reactions, have already been reported [20][21]. In context with