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

• hydroperoxide (which would presumably lead to heterolytic fragmentation) and activation of the peroxide C–O was clearly disfavored relative to activation of the alkoxide C–O bond. Rapid alkoxide metathesis was also observed in the presence of a strong Brønsted acid. Our observations suggest that the seeming

Development of an additive-controlled, SmI₂-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination

• Brice Sautier,
• Karl D. Collins and
• David J. Procter

Beilstein J. Org. Chem. 2013, 9, 1443–1447, doi:10.3762/bjoc.9.163

• improved selectivity for spirolactone 2b. We believe that spirolactones such as 2b undergo retro-aldol fragmentation (to give products such as 4b) upon prolonged exposure to Lewis acidic Sm(II)/(III)-species present in the reaction mixture. Pleasingly, the process proved general, affording the desired

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• interconverting 9 and 10 through 8 [22][23][24][25][26][27][28][29][30] might occur (see below). A mechanism on the fragmentation of initially formed metal–organic complexes, giving β-ketoalkyl radicals [40], cyclopropoxy radicals [25][28][48][49][50], or β-metalated carbonyls [39], is still controversial [35][36

• , 1547, 1449, 1298, 1229, 912, 731; HRMS–ESI (m/z): [M + Na]+ calcd for C18H23NO2, 308.1621; found, 308.1622. Radical anion and cation probe substances I and II, possessing 5-hexenyl structures. Comparison of fragmentation reaction pathways of organic radical ions generated under the redox-reagent

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

• M−1s−1 [19]) trapping trans,cis peroxyl radicals before they underwent β-fragmentation (Scheme 5). In accordance with this free-radical mechanism, Schmidt and Alexanian more recently reported the aerobic dioxygenation of alkenyl N-aryl hydroxamic acids (Scheme 6) [21]. In this case dioxygenation

A study on electrospray mass spectrometry of fullerenol C₆₀(OH)₂₄

• Mihaela Silion,
• Andrei Dascalu,
• Mariana Pinteala,
• Bogdan C. Simionescu and
• Cezar Ungurenasu

Beilstein J. Org. Chem. 2013, 9, 1285–1295, doi:10.3762/bjoc.9.145

• compounds in aqueous and ammonia media, in both negative and positive ionization mode at a capillary voltage of 4.5 kV and a fragmentor voltage of 400 V with no C60-cage fragmentation. Results and Discussion Nomenclature and ionization mechanisms In the discussion, we will use the expressions protonated [M

• impact on the sensitivity and fragmentation. Consequently, the first objective was to find the optimum values for the fragmentor and capillary voltage that provides a strong molecular ion and a good relative abundance. The use of high voltages generates a greater signal, but this needs to be balanced

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization

• John Moraes,
• Kohji Ohno,
• Guillaume Gody,
• Thomas Maschmeyer and
• Sébastien Perrier

Beilstein J. Org. Chem. 2013, 9, 1226–1234, doi:10.3762/bjoc.9.139

• Sustainability, School of Chemistry, The University of Sydney, NSW 2006, Australia 10.3762/bjoc.9.139 Abstract We describe the use of one of the most advanced radical polymerization techniques, the reversible addition fragmentation chain transfer (RAFT) process, to produce highly functional core–shell particles

• structure of the resulting polymeric chain. Among the many techniques of LRP reported to date, reversible addition–fragmentation chain transfer (RAFT) polymerization is one of the most versatile processes, both in terms of tolerance towards a wide range of monomer functionality and reaction conditions [2

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

• molecular O2 to give peroxy radical III. Probably further reaction of III with Cu(I) species gives Cu(II)-peroxide IV, which undergoes fragmentation to give aldehyde V [16][17][18], which in turn cyclizes to afford hemiacetal 2a. Protonation of Cu(II)-peroxide IV followed by the reduction of the resulting

• hydroperoxides 1 prior to the 1,5-H radical shift (Scheme 4). Presumably, radical fragmentation of O-radicals occurs to give the corresponding ketones 7, which are reduced by LiAlH4 in the next step to give alcohols 6 (Scheme 4). The reaction of a secondary hydroperoxide such as 1o, however, afforded C–H

• 3% yields, respectively, via the desired 1,4-dioxygenation, while benzophenone (7b) was also formed in 30% yield through fragmentation of the transient alkoxy radical (Scheme 4). Use of 40 mol % of NHPI slightly improved the yields of 1,4-dioxygenation products 2i and 3i (40% and 4% yields

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• leukemia [12][13][14]. Fragmentation of 3 under acidic conditions delivers two structural units, desacetylvindoline and velbanamine (2) [15]. The reassembling of catharanthine (1) and vindoline (5) into the parent alkaloids 3 and 4 by using FeCl3-promoted oxidative coupling supports the biogenesis of

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• silyl, stannyl, t-Bu group or a hydrogen [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]), unimolecular fragmentation was possible and gave neutral alkyl radicals (D•) with a reasonable (0.1 or higher) quantum yield (Scheme 1, step b) [5]. Addition to the aromatic radical anion and re

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

• epoxide as an allylating agent are displayed in Scheme 27 [59]. The first corresponds to the allylation of cyclobutyl xanthate 143 with vinyl epoxide 144 to yield compound 145, while the second involves an addition–fragmentation of xanthate 146 on β-pinene to give xanthate 147, which is then subjected to

Preparation of mixed trialkyl alkylcarbonate derivatives of etidronic acid via an unusual route

• Petri A. Turhanen,
• Janne Weisell and
• Jouko J. Vepsäläinen

Beilstein J. Org. Chem. 2012, 8, 2019–2024, doi:10.3762/bjoc.8.228

• ) and its major fragmentation at m/z = 332 were the major peaks in the positive-mode mass spectrum. Interestingly, the signal from expected compound 9 (C15H26O14P2 + Na, m/z = 515) was not seen in the positive mode; however, in the negative mode signals m/z = 332 and 515 were the major peaks, but

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• controlled conditions such as reversible addition–fragmentation chain-transfer polymerization (RAFT) or atom-transfer radical polymerization (ATRP) [14][15][16]. However, up to now, only a little is known about the preparation of dye-end-group-labeled polymers by using classical free-radical polymerization

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

• Kyle F. Biegasiewicz,
• Michelle L. Ingalsbe,
• Jeffrey D. St. Denis,
• James L. Gleason,
• Junming Ho,
• Michelle L. Coote,
• G. Paul Savage and
• Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

• /fragmentation to afford benzaldehyde, which further reacts to give benzyl benzoate [18]. Recently, we synthesized the first cubane-based Schiff base ligand (Figure 1) and screened it in the Henry reaction in the synthesis of β-nitroalcohols [19]. The cubyl moiety can be considered a cross between a tert-butyl

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

• Anthony R. Martin,
• Anthony Chartoire,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2012, 8, 1637–1643, doi:10.3762/bjoc.8.187

• free carbene in situ. The expected [Pd(IPr*Tol)(cin)Cl] was then obtained in an excellent yield (97%) by a simple fragmentation of the palladium dimer [{Pd(cin)(µ-Cl)}2] using the free carbene solution (Scheme 1). The newly synthesized complex 4 was unequivocally characterised by X-ray diffraction [24

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• dihydronepetalactone. Though the fragmentation pattern showed some similarities to that of the cis-fused iridomyrmecin (1), a comparison with mass spectral data published for the trans-fused isoepiiridomyrmecin (2) suggested that the substances Y and Z are trans-fused iridomyrmecins. While the plotted mass spectrum of

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• analysis (GC/CIMS) showed the molecular mass of the compound to be M+ = 168, while high resolution mass spectrometry (GC/HRMS) proved its atomic composition to be C10H16O2, suggesting an oxygenated monoterpene as the target structure. The fragmentation pattern, exhibited in the 70 eV EI-mass spectrum

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• considered. Keywords: diradicals; mechanisms; photochemistry; Introduction Photoinduced ring-opening or ring-fragmentation processes constitute an important type of reaction in organic photochemistry and have been examined both from a mechanistic and a synthetic point of view [1][2][3][4][5]. Mechanistic

• reactions in low-temperature matrices are the most efficient synthetic route to cyclobutadiene and its derivatives [10][11][12]. Mechanistic aspects of the photoinduced fragmentation of carbonate esters have been discussed. Thus, Griffin et al. reported that carbene intermediates are formed upon irradiation

• cyclic carbonates 1a and 1b (Scheme 1) generate products derived from 1,3-diradical intermediates [14]. Interestingly, the photoinduced fragmentation reactions of nitrogen- and oxygen-containing functionalities have been studied intensively, whereas reports on photoextrusion reactions of sulfur

Hybrid super electron donors – preparation and reactivity

• Jean Garnier,
• Douglas W. Thomson,
• Shengze Zhou,
• Phillip I. Jolly,
• Leonard E. A. Berlouis and
• John A. Murphy

Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112

• solvent DMF [14][15], and if the experiment were conducted with no excess of NaH base, 3 could itself act as a base. Protonation of 3 would afford 36, capable of undergoing spontaneous fragmentation to 35 [40][41][42][43] thereby lowering the concentration of donor. However, excess sodium hydride can

• this problem. Protonation of 2 leads to 41, and it is likely that the equilibrium fragmentation of this compound to 42 is less favourable than the fragmentation of 36 to 35 because of the restriction imposed by the second trimethylene bridge [16]. (Compound 41 has not previously been reported, but its

• protonation, then it should undergo easy fragmentation to 45, featuring a pyridinium salt and an imidazolylidene, and in these circumstances, it would be difficult to understand why this electron-donor system works well. However, if isomeric compound 44 is the product of protonation, then its fragmentation to

The use of glycoinformatics in glycochemistry

• Thomas Lütteke

Beilstein J. Org. Chem. 2012, 8, 915–929, doi:10.3762/bjoc.8.104

• peaks that are observed in a spectrum are compared to theoretically derived fragment masses that are computed from glycan structures stored in a carbohydrate database. This approach, however, is limited by the content of the database that provides the templates for in silico fragmentation, which means

Identification and isolation of insecticidal oxazoles from Pseudomonas spp.

• Florian Grundmann,
• Veronika Dill,
• Andrea Dowling,
• Aunchalee Thanwisai,
• Edna Bode,
• Narisara Chantratita,
• Richard ffrench-Constant and
• Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85

• additional oxazole derivative, but which was only produced in minute amounts. WS-30581 A (6) was identified by comparing the retention time and the MS fragmentation (Supporting Information File 1, Figure S2) of the product contained in the extract, with a synthesized compound. All oxazoles showed a

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

• the level of diastereoselectivity was only low to moderate, and the interpretation should therefore not be exaggerated. Alternative conformations explaining the results are certainly possible. The fragmentation of the primarily formed allenyl N-hydroxylamines of type 2 leading to 1,3-dienes such as 4

Volatile organic compounds produced by the phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria 85-10

• Teresa Weise,
• Marco Kai,
• Anja Gummesson,
• Armin Troeger,
• Stephan von Reuß,
• Silvia Piepenborn,
• Francine Kosterka,
• Martin Sklorz,
• Ralf Zimmermann,
• Wittko Francke and
• Birgit Piechulla

Beilstein J. Org. Chem. 2012, 8, 579–596, doi:10.3762/bjoc.8.65

• fragmentation due to the relatively high setting of the extraction/drift-tube voltages. Therefore, the m/z values of 41, 43, 57, 71, especially, may be fragments of short-chain alkylketones and aldehydes, as reported by Blake et al. in 2006 [54]. Changes in the compositions of headspace volatiles of Xanthomonas

• . Drift tube pressure was set to 2.0 mbar and drift voltage to 600 V. These settings resulted in very sensitive measurements, but some side reactions led to fragmentation of, e.g., aldehydes, as described for a SWIFT instrument by Blake et al. [54]. Mass-to-charge ratios from 20 to 250 unified mass units

Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

• Caterina Fraschetti,
• Matthias C. Letzel,
• Antonello Filippi,
• Maurizio Speranza and
• Jochen Mattay

Beilstein J. Org. Chem. 2012, 8, 539–550, doi:10.3762/bjoc.8.62

• fragmentation products. The distribution of the quasi-enantiomer fragments points to the same relative stability for the starting diastereomeric [C∙H∙N1]+ complexes and an appreciable energy difference between the diastereoisomers of [C∙H∙N2]+ ([C∙H∙N2]+hetero > [C∙H∙N2]+homo). The combination of the dependence

Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• characteristic fragment ions at m/z = 87 and m/z = 74 similar to the unbranched FAMEs, but in contrast the β-cleavage was more important than the McLafferty fragmentation (cf. Figure 5C for mass spectrum of methyl 4-methyldodecanoate). This, together with an almost completely missing fragment ion at m/z = 101

• , accounting for a γ-cleavage in unbranched FAMEs, suggested the presence of a methyl group in a γ-position, which leads to a γ-fragmentation with m/z = 115. A synthesis of methyl 4-methyldodecanoate (90) was performed starting from 10 (Scheme 3). Reduction to the aldehyde 123d and subsequent Horner–Wadsworth

• overall expected fragmentation pattern (Figure S4 of Supporting Information File 1). The transamination product of valine, 2-oxoisovaleric acid, can be used by most organisms for the biosynthesis of the leucine precursor 2-oxoisocaproic acid. The enzymes for catalysis of this pathway are encoded in the