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

• peroxides are based on three key reagents: oxygen, ozone, and hydrogen peroxide. These reagents and their derivatives are used in the main methods for the introduction of the peroxide group, such as the singlet-oxygen ene reaction with alkenes, the [4 + 2]-cycloaddition of singlet oxygen to dienes, the

• peroxide moiety, the Isayama–Mukaiyama peroxysilylation, and reactions involving peroxycarbenium ions. Syntheses employing hydrogen peroxide and the intramolecular Kobayashi cyclization are less frequently used. 1.1. Use of oxygen for the peroxide ring formation The singlet-oxygen ene reaction with alkenes

Alternaric acid: formal synthesis and related studies

• Michael C. Slade and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19

• is a benzyl ester analogue of one of Trost’s substrates employed in the ruthenium-catalyzed Alder–ene reaction [25]. It too proved to be a successful substrate for the reaction with alkyne 14, affording the 1,4-diene product 15 in 52% yield. This sequence thus demonstrated a second avenue for

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• cocatalysts for iminium activated reactions of α,β-unsaturated aldehydes with enamides [62]. The demonstration of general base catalysis for these reactions furthermore rules out Hayashi’s proposal of a concerted ene reaction for the formation of tetrahydropyridines by the diphenylprolinol-catalyzed reaction

Combined bead polymerization and Cinchona organocatalyst immobilization by thiol–ene addition

• Kim A. Fredriksen,
• Tor E. Kristensen and
• Tore Hansen

Beilstein J. Org. Chem. 2012, 8, 1126–1133, doi:10.3762/bjoc.8.125

• water and copolymerized on heating by thiol–ene additions. The resultant spherical and gel-type polymer beads have been evaluated as organocatalysts in catalytic asymmetric transformations. Keywords: asymmetric catalysis; Cinchona derivatives; organocatalysis; polymerization; thiol–ene reaction

• of thiol and alkene functionalities was adjusted to be close to unity, and the thiol–ene reaction usually has a high degree of conversion; however, the presence of free thiol groups is probably unavoidable. We were, nevertheless, curious to investigate how these supported organocatalysts would

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• (Figure 1) by retro-nitroso-ene reaction was discussed in earlier work [13], but the formation of pyrrole derivative 5 is unprecedented for the reactions of nitrones and lithiated alkoxyallenes. The 1H NMR spectrum of 5 shows four singlets (3H each) assigned to three methyl groups and one methoxy

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• 242 could be transformed to cross-conjugated trienes 243 via rearrangement with [(Ph3PAu)3O]BF4 as the catalyst [121]. Computational results indicated that the ene-reaction proceeded through a unique nucleophilic addition of an allene double bond to a cationic phosphine-gold(I)-complexed phosphine

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• therefore 5-endo cyclization is favored in the conversion of acetylenic dicarbonyl compounds. Notably, Toste and co-workers also reported a valuable gold-catalyzed enantioselective variant of the Conia-ene reaction between ß-dicarbonyl compounds and alkynes [107]. Barluenga and co-workers successively

Gold-catalyzed alkylation of silyl enol ethers with ortho-alkynylbenzoic acid esters

• Haruo Aikawa,
• Tetsuro Kaneko,
• Naoki Asao and
• Yoshinori Yamamoto

Beilstein J. Org. Chem. 2011, 7, 648–652, doi:10.3762/bjoc.7.76

• , cyclopentenyloxytrimethylsilane (1b), with 2b in the presence of the gold catalyst gave the corresponding benzylated product 3b in 61% yield (entry 1). It is worth mentioning that benzo-fused silyl enol ether 1c is suitable for this transformation as shown in entries 2 and 3, whereas it cannot be used for ene-reaction due to the

A surprising new route to 4-nitro-3-phenylisoxazole

• Henning Hopf,
• Aboul-fetouh E. Mourad and
• Peter G. Jones

Beilstein J. Org. Chem. 2010, 6, No. 68, doi:10.3762/bjoc.6.68

• precursor 5, an addition product of HNO2 to the substrate 1 by a formal hetero Alder-ene reaction. Isoxazole 6 could then undergo electrophilic substitution via 7 to afford the nitroso compound 8, which in a final step would be oxidized to 4 under the reaction conditions. Previously reported approaches to 4

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

• -hydroperoxy homoallylic alcohols (prepared by the ene reaction of the allylic alcohols mesitylol and methyl 4-hydroxytiglate, respectively, with singlet oxygen) to give spiroannulated 1,2,4-trioxanes 5a–5e and 9a–9e, respectively. A second series of 3-arylated trioxanes 10a–10h, that are available from the

• hydroperoxy alcohol 4 and benzaldehyde derivatives, was investigated by X-ray crystallography. Keywords: ene reaction; peracetalization; peroxides; singlet oxygen; trioxanes; Introduction The antimalaria-active molecule artemisinin (1) is a naturally occurring sesquiterpene peroxide with remarkable

• singlet oxygen ene reaction of allylic alcohols as a route to ß-hydroperoxy alcohols that can be transformed into 1,2,4-trioxanes by reaction with carbonyl compounds in the presence of Lewis acids [11]. This approach leads to simple cyclic peroxides (e.g. 2) which in some cases show similar antimalarial

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• -diarylalkanes starting from electron-rich arenes and styrenes. Additionally, they found that heating of styrene 41 in the presence of catalytic amounts of BiCl3 yielded substituted dihydroindenes 42 as a result of styrene dimerization. This reaction may proceed via an intermolecular ene reaction between styrene

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• C–C bond forming reaction that has been studied in flow is the PyBox-metal complex-catalyzed carbonyl ene reaction [29]. Salvadori and co-workers described the use of a flow reactor comprised of a stainless steel column packed with PyBox ligand functionalized polystyrene 13 for the ene reaction of

• in the near future. Enantioselective addition of trimethylsilyl cyanide to benzaldehyde. Asymmetric catalytic hydrogenation in a falling-film microreactor. Aldol reaction catalyzed by 5-(pyrrolidine-2-yl)tetrazole. Enantioselective addition of diethylzinc to aryl aldehydes. Glyoxylate-ene reaction in

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• by conversion to the epoxide 80. Addition of the C3-C13 fragment in a copper-catalyzed Grignard reaction afforded 81. The butenolide ring in 4,5-dehydro-cis-solamin (83) was put in place using a ruthenium catalyzed Alder-ene reaction of 81 with 82. Final selective reduction of the 4,5-double bond

• deprotected product (−)-93. Finally, the introduction of the butenolide segment using a ruthenium(II)-catalyzed Alder-ene reaction followed by selectively reduction furnished cis-solamin (71a). Spectroscopic data for this compound were identical to those reported for cis-solamin isolated from natural sources

The first organocatalytic carbonyl- ene reaction: isomerisation- free C-C bond formations catalysed by H-bonding thio- ureas

• Matthew L. Clarke,
• Charlotte E. S. Jones and
• Marcia B. France

Beilstein J. Org. Chem. 2007, 3, No. 24, doi:10.1186/1860-5397-3-24

• turnover frequencies. Background The intermolecular carbonyl-ene reaction is a useful and completely atom-efficient C-C bond forming reaction. These reactions take place without a catalyst at relatively high temperatures (>150°C), but are more often carried out with either a stoichiometric or catalytic

• Lewis acid catalyst. [1][2][3][4] One of the drawbacks of the intermolecular carbonyl ene reaction is substrate scope. The majority of all successful catalytic ene reactions have utilised the highly activated glyoxylate esters as enophile. Extending asymmetric intramolecular carbonyl ene reactions to

• polymerised under the reaction conditions. An exception was the ene reaction of ethyl trifluoropyruvate 2 with alkenes which actually took place very readily, although sometimes accompanied by isomerisation and other side products. This type of ene reaction has recently been explored by other groups using Pd