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

• in combination with a catalytic amount of TEMPO have already been reported in highly selective oxidations of alcohols to carbonyl compounds [14]. The development of efficient flow-reactor systems for molecular transformations is an important area in organic synthesis. The introduction of more general

• for alcohol oxidations. Oxidation–condensation sequence in the synthesis of 2,3-dimethylquinoxaline. Products and yields in the oxidation of alcohols performed in a tubing reactor at a total flow rate of 0.4 mL/min (residence time: 4.5 min) at 35 °C. Acknowledgements We thank the Schlumberger

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

• . Metal-free PINO activation represents another decisive step towards the consecration of NHPI as the mediator of first choice to perform green and selective aerobic oxidations. The next one would be the engineering of valuable solutions for the complete recovery and recycle of this homogeneous

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• dihydroquinazolines vasicine (1) and deoxyvasicine (2) can be synthesized from their corresponding aminals by using an iodine-promoted oxidation [34]. While resulting in good yields, these oxidations have the drawback of requiring large amounts of a strong oxidant for the permanganate oxidation and the necessity of

• strong bases. Han et al. have recently shown the ability of copper salts, in conjunction with oxygen, to catalyze oxidations of 2-substituted tetrahydroquinazoline aminals to quinazolines [35] (Figure 2). In addition, Reddy and co-workers have developed a catalytic system in which 2,3-substituted

• aminals. Here we present catalytic methods for the synthesis of both these compound classes from aminals using Cu(OAc)2/O2/AcOH and KI/TBHP systems, respectively. Results and Discussion Copper-catalyzed oxidations of aminals to dihydroquinazolines Copper-catalyzed oxidation reactions have received a great

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• amination reactions [53][54], photodimerization studies [55], MnO2 oxidations [56] and during phase-transfer reactions [57]. The use of high-resolution cameras to specifically examine physical effects during the merging of sonochemistry and microfluidic techniques, leading to improved reactor design, was

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

• enhanced catalyst loading; however, aerobic oxidations of these highly electron-rich compounds are barely described in the literature, and to the best of our knowledge this is the first metal-free example that even proceeds at room temperature. (Examples for metal-catalyzed aerobic oxidations can be found

Regio- and stereoselective oxidation of unactivated C–H bonds with Rhodococcus rhodochrous

• Elaine O’Reilly,
• Suzanne J. Aitken,
• Gideon Grogan,
• Paul P. Kelly,
• Nicholas J. Turner and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2012, 8, 496–500, doi:10.3762/bjoc.8.56

• ][14]. In light of this, we have explored the ability of this strain to perform regio- and stereoselective oxidations of selected protected heterocyclic substrates. Protected substrates are of particular interest, as subtle changes in the protecting group have been shown to affect the regioselectivity

Tertiary alcohol preferred: Hydroxylation of trans-3-methyl-L-proline with proline hydroxylases

• Christian Klein and
• Wolfgang Hüttel

Beilstein J. Org. Chem. 2011, 7, 1643–1647, doi:10.3762/bjoc.7.193

• approach whose potential has not yet been fully exploited is the stereospecific hydroxylation of tertiary alkyl moieties with oxygenases. Most oxidations to tertiary alcohols described so far were observed during degradation of steroids and other terpenoid bioactive compounds by microbial whole cells [10

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

• 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

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

• Povarov adducts in oxygenated atmospheres also affords the oxidation–elimination products 5 and 8 (Scheme 2) [8][12][20]. The alternative oxidation–elimination pathway is predominant in some CAN-promoted oxidations of different Povarov adducts 3. Incidentally, this reagent is also used as a catalyst in

• - and N-substituents [22][23][24][25] (for related isoquinoline oxidations, see [26][27]). Related oxidative processes involve, for instance, a cascade Povarov–hydrogen transfer reaction using Tf2NH as a catalyst and the imine as an oxidant, as recently described [28]. In addition, Povarov adducts

Gold-catalyzed oxidation of arylallenes: Synthesis of quinoxalines and benzimidazoles

• Dong-Mei Cui,
• Dan-Wen Zhuang,
• Ying Chen and
• Chen Zhang

Beilstein J. Org. Chem. 2011, 7, 860–865, doi:10.3762/bjoc.7.98

• –carbon triple bonds by homogeneous gold catalysts was reported recently [28][29][33]. To the best of our knowledge, gold and other transition metal-catalyzed oxidations of allenes have not been reported [37][38]. In the context of ongoing studies on metal-catalyzed atom-economical reactions, we have been

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• of the TTF dication hinders subsequent removal of an electron from the thiophene units, so further oxidations are beyond the electrochemical window of the solvent. Compound 28 is reversibly oxidised to 28+· at −740 mV, within the range seen in other nickel dithiolene complexes. A second single

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• by cyclic voltammetry in the anodic region (scan area up to 1.5 V). The reversible first oxidations to the radical cations of monophenothiazines 2a, 2b, and 4 were shifted anodically in comparison to unsubstituted monophenothiazines [54] as a consequence of the electron-withdrawing nature of the

• thioacetate. Due to unsymmetrical substitution, the dyad 2c showed two distinctly separated, reversible oxidations at E00/+1 = 668 mV and E0+1/+2 = 853 mV. The cyclic voltammogram of the triad 2d displayed three distinctly separated, reversible oxidations at E00/+1 = 608 mV, E0+1/+2 = 765 mV, and E0+2/+3

• = 876 mV (Figure 2). However, the electrochemistry of the tetrad 2e is more complicated. Only three distinctly separated, reversible oxidations were evident. The first oxidations at E00/+1 = 597 mV and E0+1/+2 = 690 mV are in accordance with Nernstian behavior, while the third oxidation at E0 = 842 mV

The development and evaluation of a continuous flow process for the lipase- mediated oxidation of alkenes

• Charlotte Wiles,
• Marcus J. Hammond and
• Paul Watts

Beilstein J. Org. Chem. 2009, 5, No. 27, doi:10.3762/bjoc.5.27

• biocatalyst with respect to peracid formation, facilitating a series of oxidations including alkenes [21] and ketones via the Baeyer–Villiger reaction [22] and retaining the broad substrate specificity of Candida antarctica lipase B. In the past decade micro reactors, and more generically continuous flow

• peracid, enabling greater system flexibility, along with evaluating the methodology towards other synthetically useful oxidations. Experimental Materials 1-Methylcyclohexene (6, 99%, Aldrich), styrene (9, ReagentPlus®, ≥ 99%, Aldrich), cis-stilbene (11, 96%, Aldrich), trans-stilbene (12, 96%, Aldrich

Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• Information File 62: Experimental and spectroscopic data for: Green oxidations: Titanium dioxide induced tandem oxidation

A biphasic oxidation of alcohols to aldehydes and ketones using a simplified packed- bed microreactor

• Andrew Bogdan and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2009, 5, No. 17, doi:10.3762/bjoc.5.17

• characterization of a simplified packed-bed microreactor using an immobilized TEMPO catalyst shown to oxidize primary and secondary alcohols via the biphasic Anelli-Montanari protocol. Oxidations occurred in high yields with great stability over time. We observed that plugs of aqueous oxidant and organic alcohol

• higher degree of safety [1][2][3][4][5][6][7][8][9][10][11][12]. Alcohol oxidations are well suited for microreactors due to high by-product formation, catalyst contamination and safety concerns often associated with scale-up in batch reactors [13]. Recent developments in microreactor technology and

• solid-supported catalysis have aimed to solve these issues. Numerous flow oxidations have been presented in the literature [13][14][15][16], however many rely on stoichiometric reagents [17][18], suffer from catalyst deactivation [19][20], or rely on soluble catalysts [21], all of which limit their

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• E. J. Behrman Department of Biochemistry, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA 10.1186/1860-5397-2-22 Abstract This paper reviews the recent literature on the title reactions and updates a 1988 review. The Elbs and Boyland-Sims oxidations are shown in Scheme 1

• area is the use of salts of peroxydisulfate which are soluble in organic solvents by virtue of large organic cations in place of the commercially available ammonium, sodium, or potassium salts. This approach has not yet been reported for the Elbs or Boyland-Sims oxidations. Corresponding chemistry of

• Boyland (1905–2002) has appeared. [34][35][36] The Tables record the literature on the Elbs and Boyland-Sims oxidations from 1984 (the approximate literature cutoff for ref. 1) through mid-2006. There are also a few earlier references which were omitted from ref. 1. Key to the Tables: the Tables are

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

• shows that the thermally stable phenylacetone monooxygenase (PAMO) and recently engineered mutants can be used as a practical catalysts for enantioselective Baeyer-Villiger oxidations of several ketones on a preparative scale under in vitro conditions. For this purpose several parameters such as buffer

• composition, the nature of the solvent system and the co-factor regeneration system were optimized. Overall a fairly versatile and efficient catalytic system for enantioselective laboratory scale BV-oxidations of ketones was developed, which can easily be applied even by those organic chemists who are not

• (NAD(P)H) for reductive O2-activation.[33][34][35] Another challenge is the cost-factor of the BVMOs themselves, since their use usually requires tedious purification steps. These complications are frequently addressed by performing biocatalytic BV-oxidations in vivo, i.e., using whole, metabolically