Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• . Many investigations on oxygenation reactions have been carried out by using a simple, readily available reagent system mimicking monooxygenase enzymes. An interesting system for the oxidation of aliphatic hydrocarbons, consisting of oxygen, powdered zinc, pyridine, acetic acid, and a catalytic amount

• ]. In Gif systems pyridine is not only used as a solvent but it also acts as a ligand on the iron complex [28]. Different Fe(II) or Fe(III) picolinate (PA) and dipicolinate (DPA) complexes as catalysts of oxygenation reactions have been studied by the Sawyer [29][30][31], Barton [31][32], and Kotani

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

• triarylpyrylium salts, as they have excited state reduction potentials in excess of +1.7 V vs SCE (Scheme 2) [20]. In addition, prior work demonstrates that these catalysts are productive in cation radical mediated [4 + 2], [2 + 2], oxygenation, and rearrangement chemistry [21][22]. We also sought to delineate

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

• proceeds through a formation of an enol-containing complex with a metal ion (Scheme 57, Table 14). 3.3. Oxidation of 1,5-dienes in the presence of thiols The co-oxidation of 1,4-dienes and thiols (thiol–olefin co-oxygenation, TOCO reaction) was described for the first time by Beckwith and Wagner as a

The myxocoumarins A and B from Stigmatella aurantiaca strain MYX-030

• Tobias A. M. Gulder,
• Snežana Neff,
• Traugott Schüz,
• Tammo Winkler,
• René Gees and
• Bettina Böhlendorf

Beilstein J. Org. Chem. 2013, 9, 2579–2585, doi:10.3762/bjoc.9.293

• O-methylation, glycosylation, prenylation, oxygenation and subsequent cyclization or dimerization events [34]. Nitrogen-bearing congeners are rather scarce, with the bacterial aminocoumarins, such as the gyrase inhibitor novobiocin, being the most well-known examples [35]. Despite the larger number

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• multifunctionalization reactions of various alkenes 5–14 (Table 2). The oxynitration of olefins and the direct oxygenation of methyl C–H bonds of branched aliphatic alkenes 5–10 occurred to afford triple functionalized products 15–20 (Table 2, entries 1–6). In the reactions of alkenes 5 and 7, a remarkable

• hydroxy group arising from hydration of the olefin (entry 6). Functionalization reactions involving oxygenation of methylene C–H bonds of alkenes 11–13 also proceeded to afford secondary nitrate compounds 21–23, though no diastereoselectivity was observed (Table 2, entries 7–9). Unfortunately, no tertiary

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• the reaction. Results and Discussion Synthesis of cyclopropylenyne and reductive coupling with model epoxide Diethyl 1,3-acetonedicarboxylate (Scheme 4, 16) was rapidly identified as an inexpensive five-carbon fragment possessing the appropriate oxygenation pattern for preparation of the C1–C9 enyne

• , however, enyne 6 proved to be quite stable and could be stored for extended periods at 0–5 °C without appreciable isomerization or decomposition. With a suitable cyclopropylenyne in hand, a model epoxide substrate containing the 1,3-oxygenation pattern found in ripostatin A (Scheme 5) was prepared by

• epoxides, the olefin coordinates to nickel and directs alkyne insertion. Because of this directing effect, formation of the regioisomeric diene product is atypical for reductive coupling reactions of enynes and epoxides. However, in reactions of 1-phenyl-1-propyne and epoxides with oxygenation in the 3

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

• complexes. However, eco-friendly standards, including the demand for highly selective transformations, impose the development of metal-free processes, especially for large-scale productions, as in the case of the oxygenation of hydrocarbons. For this reason, many efforts have been devoted in the past decade

• processes, especially in the field of the selective oxygenation of hydrocarbons. Review Radical initiation by thermal decomposition Thermal decomposition of peroxides and azo-compounds is a well-known technique generally used to generate radicals in solution. Ishii and co-workers widely investigated the key

• system was also applied to the oxygenation of 1,3,5-triisopropylbenzene [17]. However, in this case the conversion of all isopropyl groups was far from being reached, with mono- and di-phenols being the major products, while the yield in benzene-1,3,5-triol was close to 1%. Sheldon and co-workers tested

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

• . Similarly, it was also revealed that the sp3 C–H oxygenation could proceed directed by the N–H ketimine moieties under Cu-catalyzed aerobic conditions via the corresponding iminyl radical species, where 1,2-diacylbenzenes and amino endoperoxides could be synthesized by C–H oxygenation of secondary and

• presence of Et3N (2 equiv) in DMF, the reaction proceeded at room temperature for 17 h to afford C–H oxygenation products, cyclic hemiacetal 2a and 1,4-diol 3a in 49% and 8% yields, respectively (Table 1, entry 1). It was found that addition of nitrogen ligands such as 2,2’-bipyridine and 1,10

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• the lower-power light source. These longer residence times further lowered the reactor productivity to 0.15 mmol/h [24]. Photooxygenations Direct oxygenation of organic molecules through the photosensitised addition of singlet oxygen represents an atom-economic method of functionalisation and is

• have been employed in the Rose Bengal-sensitised oxygenation of cyclopentadiene 19 (Scheme 7) [30][31]. Although this method allowed good temperature control and the immediate quenching of the potentially explosive peroxide intermediate 20 as it formed, the process was low yielding (20%), and whilst

• one common issue with moving to microflow photochemistry: although yields may increase, productivity can be significantly lower. A glass-loop microreactor was employed in the sensitised oxygenation of (−)-β-citronellol (24) shown in Scheme 9, an important reaction for the synthesis of the fragrance

Enantioselective total synthesis of (R)-(−)-complanine

• Krystal A. D. Kamanos and
• Jonathan M. Withey

Beilstein J. Org. Chem. 2012, 8, 1695–1699, doi:10.3762/bjoc.8.192

• MacMillan imidazolidinone (5R)-2,2,3-trimethyl-5-benzyl-4-imidazolidinone [8] with 4-nitrobenzoic acid as cocatalyst, all efforts to effect benzoylation of 3, yielding 5, were unsuccessful, and this route was ultimately abandoned as attention turned to more conventional α-oxygenation strategies and a

• stepwise approach to 4. The reaction of aldehydes with nitrosobenzene in the presence of proline-derived secondary amine catalysts represents the current benchmark in organocatalytic α-oxygenation strategies [9]. A known drawback of this approach is the instability of the oxyaminated products, presumably

• catalyst, resulted in clean α-oxygenation (Scheme 4). Attempts to effect the direct conversion of 7 to amino alcohol 4, by using the aldoximine approach described above (Scheme 3), yielded a complex mixture of products. However, 6 was readily isolated as oxyaminated alcohol 7, following in situ reduction

Asymmetric one-pot sequential Friedel–Crafts-type alkylation and α-oxyamination catalyzed by a peptide and an enzyme

• Kengo Akagawa,
• Ryota Umezawa and
• Kazuaki Kudo

Beilstein J. Org. Chem. 2012, 8, 1333–1337, doi:10.3762/bjoc.8.152

• followed by oxygenation at the α-position of the carbonyl group. If such a sequence can be realized in a one-pot reaction, it would be a powerful method for the synthesis of oxy-functionalized indole derivatives with operational simplicity. To date, there has been no report on the FCAA reaction combined

• with an α-oxygenation of aldehydes [24][25][26][27][28][29] in a one-pot sequential reaction. Meanwhile, our group has developed resin-supported peptide catalysts (Figure 2) for several organic reactions in aqueous media [30][31][32][33][34][35][36][37]. Since these catalysts can be applicable for the

• -oxyamination of aldehydes catalyzed by a peptide and an oxidizing enzyme, laccase [36][38]. Because the reaction conditions for that system are mild without employing a strong oxidant, we envisaged that the sequential FCAA/α-oxygenation could be attained by adopting the peptide-and-laccase-cocatalyzed

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• , aminomethylation, sulfuration, oxygenation). However, aryllithiums can rarely be directly involved in transition-metal-catalyzed cross-coupling reactions and are usually transformed into organometallic fragments suitable for efficient Negishi, Stille, Suzuki–Miyaura, and Hiyama cross-coupling reactions [1][2

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

• fabrication, see the Supporting Information File 1); an optical image of the fabricated microreactor is shown in Figure 2. Photosensitized oxygenation was chosen as a biphasic gas–liquid reaction to study the efficiency of the triple-channel microreactor. Photooxygenations in classical reaction vessels suffer

• prevent diffusion of solvents from the middle channel to the outer channels. Thus, only oxygen diffuses into the solution and not the opposite way around. The efficiency of the triple-channel microreactor was studied by carrying out photosensitized oxygenation of citronellol, allyl alcohols, and α

• -terpinene. Photosensitized oxygenation of (−)-citronellol The photosensitized oxygenation of citronellol is an industrially important synthetic transformation [47] as it is used for bulk production of a fragrance, rose oxide (Scheme 1). The reaction was performed with methylene blue as a sensitizer in

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

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

• thermodynamically more stable indole 88. More recently, a suitable substrate for the selective oxygenation of the C9a position of a mitomycin derivative was discovered by F.E. Ziegler and co-workers [87]. The use of a Polonovski reaction [88] on the aziridinomitosane 90 gave the C9a oxygenated compound 92 in 67

Towards practical biocatalytic Baeyer- Villiger reactions: applying a thermostable enzyme in the gram- scale synthesis of optically- active lactones in a two-liquid- phase system

• Frank Schulz,
• François Leca,
• Frank Hollmann and
• Manfred T. Reetz

Beilstein J. Org. Chem. 2005, 1, No. 10, doi:10.1186/1860-5397-1-10

• equilibrium of NADPH/NADP+ to be on the reduced side. Thus, not just kinetic inhibition of the desired oxygenation reaction due to NADPH-limitation was circumvented. The stability of the cofactor itself was also increased, since NADP+ is rather unstable under basic conditions.[59] Isopropanol, being the most