Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• -heterolytic fragmentation in which either an electrofugal (E+) or nucleofugal (Nu−) group is transferred from a position adjacent to respective positively and negatively charged radical centers (Scheme 1). These fragmentation reactions produce neutral radicals, which then participate in typical radical

• reactions, including C–C bond formation and addition to unsaturated centers. Because of their importance, α-heterolytic fragmentation reactions of radical anions and cations have been intensively studied from synthetic and mechanistic perspectives [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25

• processes form zwitterionic biradical intermediates 3, in which a proton transfer and an α-heterolytic fragmentation proceeds, produce biradicals 7 that are precursors of the heterocyclic products 6 (Scheme 2). Photochemical reactions of naphthalimides with electron donors have also been intensively studied

Deoxygenative gem-difluoroolefination of carbonyl compounds with (chlorodifluoromethyl)trimethylsilane and triphenylphosphine

• Fei Wang,
• Lingchun Li,
• Chuanfa Ni and
• Jinbo Hu

Beilstein J. Org. Chem. 2014, 10, 344–351, doi:10.3762/bjoc.10.32

• formed in 69% yield (Table 1, entry 1). Surprisingly, it was found that in the absence of TBAC, PPh3 could be used both to promote the fragmentation of TMSCF2Cl and combine with the generated :CF2 (Table 1, entry 2). A rough comparison of the reaction temperatures showed that a lower temperature (rt) is

• ][20][21][22][23][24][25]. Initially it was speculated that it were trace amounts of nucleophilic impurities (such as chloride ions) that initiated the fragmentation of TMSCF2Cl to release :CF2 [31], which combined with PPh3 to form the ylide. However, the experiment at room temperature showed that

• activation of the C–Cl bond by PPh3 (Path B). In Path A, PPh3 firstly coordinates the silicon atom of TMSCF2Cl to form activated penta-coordinated silicon species 8 [41] and activates both the C–Si and the C–Cl bond. Next, the release of CF2 leads to silylphosphonium salt 9. Finally, the fragmentation of 9

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• pheromone 20 upon enzyme catalyzed fragmentation. Uncatalyzed DVCPR takes places to give 21 within short periods of time. The corresponding activation energies have been determined as well as the half-lifes at different temperatures. Bioassays proved that 20 was far more bioactive than 21, and since the

• 211 in solvent-dependent ratios. The sole product arising from the desired DVCPR via 208'' is the major product 210. The two remaining products arise from trans-silylation and fragmentation (208' to 209) or via ionic intermediate 208''' and fragmentation to give 211. The different product distribution

• apply the transition metal catalyzed 1,2-acyl shift with subsequent vinyl carbenoid formation. Propargylic acetate 251 (see Scheme 33) has been shown to undergo 5-exo-dig cyclization via 252 to give zwitterionic intermediate 253. A concomitant fragmentation reaction yielded vinyl-carbenoid 254. Uemura

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

• Moustafa Sherief Moustafa,
• Saleh Mohammed Al-Mousawi,
• Maghraby Ali Selim,
• Ahmed Mohamed Mosallam and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11

• propiolate (4a) in the presence of L-proline to produce the penta-substituted benzene derivative 13b in 60% yield (Scheme 4). In order to explain this unusual finding, we proposed that malononitrile, perhaps formed under the reaction conditions by C–C bond cleavage promoted fragmentation of 8, adds to 9 to

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

• -trioxolanes can be trapped with allyltrimethylsilane. For example, the SnCl4-mediated fragmentation of ozonides 84a–l in the presence of allyltrimethylsilane in dichloromethane gives a complex mixture of products 85–94, including dioxolanes 86a–i, 87i, 90j–l, and 91j (Scheme 25, Table 8) [256]. Treatment of

SF002-96-1, a new drimane sesquiterpene lactone from an Aspergillus species, inhibits survivin expression

• Silke Felix,
• Louis P. Sandjo,
• Till Opatz and
• Gerhard Erkel

Beilstein J. Org. Chem. 2013, 9, 2866–2876, doi:10.3762/bjoc.9.323

• . The flow rate was 0.45 mL/min. The fragmentor voltage was set to 140 V in the positive and negative APCI modes. The compound showed the highly characteristic fragmentation pattern in the APCI-positive mass spectrum revealing the pseudo-molecular ion [M + H]+ with m/z of 281.2. The purity of SF002-96-1

• Ac-DEVD-amino-4-methylcoumarin (AC-DEVD-AMC; Calbiochem, Bad Soden, Germany) for 2 h at 37 °C. AMC released from the cleavage of AC-DEVD-AMC was measured by a spectrofluorimeter with excitation and emission wavelengths of 355 nm and 460 nm respectively. Measurement of DNA fragmentation Colo 320 cells

• ) Detection of DNA fragmentation by agarose gel electrophoresis after treatment of Colo 320 cells for 5 h with different concentrations of the test compound. Control: untreated cells only. (C) Morphology analysis of the cell nuclei by DAPI staining after treatment of Colo 320 cells with 26.31 µM of SF002-96-1

[²H₂₆]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus

• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319

• shifts [10], stereospecific conversions along multistep biosynthetic pathways [11], hydride abstractions in oxidation steps [12], or deprotonations [13] are to be followed. Its incorporation is best observed by GC–MS, and if fragmentation mechanisms are known [14], the site of incorporation can be

AgOTf-catalyzed one-pot reactions of 2-alkynylbenzaldoximes with α,β-unsaturated carbonyl compounds

• Qiuping Ding,
• Dan Wang,
• Puying Luo,
• Meiling Liu,
• Shouzhi Pu and
• Liyun Zhou

Beilstein J. Org. Chem. 2013, 9, 1949–1956, doi:10.3762/bjoc.9.231

• fragmentation from 2-alkynylbenzaldoximes and α,β-unsaturated carbonyl compounds. Based on previous results [36][37][38][39][41][42][43], we expect 2-alkynylbenzaldoxime 1 to easily convert at room temperature to isoquinoline N-oxide A by a AgOTf-catalyzed cyclization. Compound A produced in situ might undergo

• a 1,3-dipolar cycloaddition with α,β-unsaturated carbonyl compound 2 leading to 2,10b-dihydro-1H-isoxazolo[3,2-a]isoquinoline intermediate B [44][45], which may then suffer a rearrangement or fragmentation resulting in compound 3 (Scheme 1) [35][36][38][42]. To demonstrate the feasibility of this

Activation of cryptic metabolite production through gene disruption: Dimethyl furan-2,4-dicarboxylate produced by Streptomyces sahachiroi

• Dinesh Simkhada,
• Huitu Zhang,
• Shogo Mori,
• Howard Williams and
• Coran M. H. Watanabe

Beilstein J. Org. Chem. 2013, 9, 1768–1773, doi:10.3762/bjoc.9.205

• –MS fragmentation of the compound matched that provided in the Ultra GC–DSQ (ThermoElectron, Waltham, MA) GC–MS database. The structure of the compound was determined by NMR analysis in CDCl3 (Table 1). The presence of two O-CH3 groups at C-2’ (δc 51.99, δH 3.94) and C-2” (δc 52.31, δH 3.88) and

Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

• Götz Bucher,
• Gernot Heitmann and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1668–1676, doi:10.3762/bjoc.9.191

• we investigate the fragmentation reactions of cyclic ketals. Three ketals with different ring sizes derived from indan-2-one were decomposed by photolysis and pyrolysis. Particularly clean is the photolysis of the indan-2-one ketal 1, which gives o-quinodimethane, carbon dioxide and ethylene. The

• mechanism formally corresponds to a photochemically allowed coarctate fragmentation. Pyrolysis of the five-ring ketal yields a number of products. This is in agreement with the fact that coarctate fragmentation observed upon irradiation would be thermochemically forbidden, although this exclusion principle

• does not hold for chelotropic reactions. In contrast, fragmentation of the seven-ring ketal 3 is thermochemically allowed and photochemically forbidden. Upon pyrolysis of 3 several products were isolated that could be explained by a coarctate fragmentation. However, the reaction is less clean and

New tridecapeptides of the theonellapeptolide family from the Indonesian sponge Theonella swinhoei

• Annamaria Sinisi,
• Barbara Calcinai,
• Carlo Cerrano,
• Henny A. Dien,
• Angela Zampella,
• Claudio D’Amore,
• Barbara Renga,
• Stefano Fiorucci and
• Orazio Taglialatela-Scafati

Beilstein J. Org. Chem. 2013, 9, 1643–1651, doi:10.3762/bjoc.9.188

• presence of the b2 fragmentation peak at m/z 331 supported, once again, the presence of the MeS(O)Ac unit. Complete acid hydrolysis of 2 and Marfey’s analysis [21] on the hydrolysate (derivatization with L-FDAA, 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide, followed by LC–MS comparison with the FDAA

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• ], reversible addition-fragmentation chain transfer (RAFT) [8][9][10], and nitroxide-mediated polymerization (NMP) [11], has opened new prospects in this research field, and permits precise tailoring of the synthetic chain length, the composition and the architecture [12]. Contrary to pullulan, dextran and

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