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

• conversion at the expense of increased dimer formation, both effects being ascribed to the greater average photon density in the flow system [70]. Mechanistic studies of the photoreduction of benzophenone (63) with benzhydrol (64) (Scheme 20) have been performed in a microflow reactor, allowing the quantum

• approach to following microphotochemical reactions by online analysis involved UV detection. The formation of benzopinacol from benzophenone was used as a model reaction and quartz reactor construction allowed both the use and detection of shorter wavelengths than would be allowed by Pyrex. The data

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

• ]. In the second experiment, the parent hydrocarbon 2 was irradiated in the presence of vinylacetylene (199) and a triplet sensitizer (benzophenone). Besides the photodimers of 199, the [2 + 2] photoadduct 200 was isolated in low yield [137]. 1.4.2 Ionic reactions Regardless of what types of reactions

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• of target complexes 19/20. It is interesting to note that the acetophenone module-derived compound 14a gave the expected enolate 16a; however, its further oxidation lead mostly to decomposition, suggesting higher instability of intermediate derivatives of type 17 and 18 [48]. Also, the benzophenone

Reactions of nitroxides XIII: Synthesis of the Morita–Baylis–Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

• Jerzy Zakrzewski

Beilstein J. Org. Chem. 2012, 8, 1515–1522, doi:10.3762/bjoc.8.171

• to [55][56][57]. Liquid aldehydes were purified by using vacuum distillation. THF was distilled over sodium under argon in the presence of benzophenone as an indicator. The experiments were performed in a 5 mL round-bottom flask, equipped with a magnetic stirrer. Most of the MBH adducts were obtained

Synthesis and evaluation of new guanidine-thiourea organocatalyst for the nitro-Michael reaction: Theoretical studies on mechanism and enantioselectivity

• Tatyana E. Shubina,
• Matthias Freund,
• Sebastian Schenker,
• Timothy Clark and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2012, 8, 1485–1498, doi:10.3762/bjoc.8.168

• over sodium/benzophenone and by distillation prior to use. Solvents for chromatography were distilled prior to use. TLC chromatography was performed on precoated aluminium silica gel ALUGRAM SIL G/UV254 plates (Macherey-Nagel GmbH & Co.). Flash chromatography was performed on silica gel 60 Å (Acros

Azobenzene dye-coupled quadruply hydrogen-bonding modules as colorimetric indicators for supramolecular interactions

• Yagang Zhang and
• Steven C. Zimmerman

Beilstein J. Org. Chem. 2012, 8, 486–495, doi:10.3762/bjoc.8.55

• , and 9 were synthesized according to the published procedures [34], as were compounds 11 and 17 [36]. Solvents were reagent grade and used without further purification except as follows: Tetrahydrofuran (THF) was distilled from sodium benzophenone ketyl immediately prior to use. Methylene chloride

Double N-arylation reaction of polyhalogenated 4,4’-bipyridines. Expedious synthesis of functionalized 2,7-diazacarbazoles

• Mohamed Abboud,
• Emmanuel Aubert and
• Victor Mamane

Beilstein J. Org. Chem. 2012, 8, 253–258, doi:10.3762/bjoc.8.26

• under an atmosphere of argon in oven-dried glassware. Toluene was distilled over sodium/benzophenone and stored over sodium. Melting points were measured on a Totoli apparatus. Proton and carbon NMR spectra were recorded on Bruker AMX-400, AC-200 or AC-250 Fourier transform spectrometers with an

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• ketone are readily tolerated. Thus, the Boc-substituted benzophenone 130 reacts with TMP2Mg·2LiCl (1.1 equiv, −20 °C, 4 h) providing the expected aryl magnesium amide 131, which after a copper-mediated benzoylation leads to the 1,2,3-trisubstituted diketone 132 in 72% yield. This reagent allows a smooth

Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• generality of the concept. Experimental General All reactions were performed under a protective argon atmosphere using standard Schlenk techniques. Hexane, THF and toluene purchased from Sigma-Aldrich, were dried by heating to reflux over sodium benzophenone ketyl and distilled under nitrogen prior to use. n

A simple and convenient one-pot synthesis of substituted isoindolin-1-ones via lithiation, substitution and cyclization of N'-benzyl-N,N-dimethylureas

• Keith Smith,
• Gamal A. El-Hiti,
• Amany S. Hegazy and
• Benson Kariuki

Beilstein J. Org. Chem. 2011, 7, 1219–1227, doi:10.3762/bjoc.7.142

• materials were obtained from Aldrich Chemical Company and used without further purification. THF was distilled from sodium benzophenone ketyl. General procedure for the synthesis of 3-substituted isoindolin-1-ones 9–18 and 20–40. A solution of t-BuLi in heptane (3.9 mL, 1.7 M, 6.6 mmol) was added to a cold

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

• Oksana Shvydkiv,
• Kieran Nolan and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

• benzpinacol 15 (Scheme 7). In acetone-d6, 14 gave singlets at 1.96 ppm for its –SCH3- and at 3.41 ppm for its –CH2S group, respectively. These values closely match those for the related benzophenone adduct [51]. The product ratio of 14/15 was determined to be 55:45. Reactor comparison Based on the conversions

• energies of DMBP (T1 = 69.4 kcal/mol or 290 kJ/mol [53]) and phthalimides (2: T1 = 71 kcal/mol or 297 kJ/mol [39]), energy transfer (Scheme 8, path A) is not very efficient but has been confirmed spectroscopically for a related N-phthalimidocarboxylate/benzophenone pair [52]. Subsequent electron transfer

• SCE) are more readily oxidized [23]. As a result, electron transfer to the triplet excited DMBP becomes energetically feasible (Scheme 8, path B) [52]. Similar electron transfer scenarios have been established for photoreactions of N-methylphthalimide or benzophenone with either thioethers [54][55] or

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride

• Sergei I. Kozhushkov,
• Alexander F. Khlebnikov,
• Rafael R. Kostikov,
• Dmitrii S. Yufit and
• Armin de Meijere

Beilstein J. Org. Chem. 2011, 7, 1003–1006, doi:10.3762/bjoc.7.113

• obtained according to the previously published procedure [21]. A 5.0 N solution of HCl in Et2O was prepared by saturation of anhydrous Et2O with gaseous HCl at 0 °C. Anhydrous diethyl ether was obtained by distillation from sodium benzophenone ketyl, acetone by distillation from anhydrous potassium

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• that the meta photocycloaddition occurs from the singlet excited-state; they observed that 6-phenyl-2-hexene undergoes cis–trans isomerization upon sensitizing with acetone and benzophenone, whereas the photocycloaddition to the meta product could only be triggered via direct irradiation [23]. Mode

• can take place to form a spiro compound; further re-aromatization to form the enol, lactolization and cyclization explains the formation of the benzoxepine structure [101]. Griesbeck et al. reported the formation of benzoxepines from the benzophenone analogue upon irradiation at slightly lower

Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

• Axel G. Griesbeck,
• Jörg Neudörfl and
• Alan de Kiff

Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60

• and ФISC < 0.01 for N-arylphthalimides [1]. If necessary, the population of the triplet state is also possible by sensitization, e.g., with triplet sensitizers such as acetone or benzophenone. With a triplet energy ET of 293–300 kJ mol−1 and a ground-state reduction potential E0 of −1.85 V vs Fc/Fc

• temperature and in ethanol at low temperatures are known: Triplet acetone, acetophenone and xanthone in acetonitrile are quenched by 1 via energy transfer; the rate constant is almost diffusion-controlled and somewhat smaller for benzophenone. The sole product from the photolysis of 1 is the double hydrogen

• measured for a series of bichromophoric systems based on phthalimide–linker–donor triades [12]. Concerning the photochemistry of 10, a remarkable difference to all other phthalimide derivatives occurred: Neither direct excitation nor triplet (acetone, benzophenone) sensitized conditions led to substrate

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• nitrogen atmosphere. Diethyl ether and tetrahydrofuran (THF) were distilled from benzophenone ketyl prior to use. 1-Ethynyl-2-methoxybenzene (4a), pivalophenone (7), n-butyllithium (1.6 M) in hexanes, 1-bromo-2-[2-(trimethylsilyl)ethynyl]benzene, triethylsilane, trifluoroacetic acid, potassium tert

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• benzophenone, a triplet-state di-π-methane rearrangement is induced. Thus, in the initial reaction step connection between one vinyl and one benzo carbon atom takes place, i.e., a so called vinyl–benzo bridging, that leads to the intermediate biradical BR1a [29]. Subsequent rearomatization with the formation

Formation of macrocyclic lactones in the Paternò–Büchi dimerization reaction

• Junya Arimura,
• Tsutomu Mizuta,
• Yoshikazu Hiraga and
• Manabu Abe

Beilstein J. Org. Chem. 2011, 7, 265–269, doi:10.3762/bjoc.7.35

• synthetically useful four-membered heterocyclic compounds, i.e., oxetanes. The Paternò–Büchi reaction of furan with a triplet carbonyl, such as n,π* triplet benzophenone, produces regioselectively 2-alkoxyoxetanes 2OX (Scheme 1). The regioselective formation is rationalized by the relative stability of the

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• ], undergo a photo-induced di-π-methane rearrangement upon triplet sensitization to give the corresponding cationic dibenzosemibullvalene derivatives [N,N-dialkyl-3,4-{8c,8e-(4b,8b-dihydrodibenzo[a,f]cyclopropa[cd]pentaleno)}pyrrolidinium derivatives]. Whereas the covalent attachment of a benzophenone

• functionality to the pyrrolinium nitrogen atom did not result in an internal triplet sensitization, the introduction of a benzophenone unit as part of the counter ion enables the di-π-methane rearrangement of the dibenzobarrelene derivative in the solid-state. Preliminary experiments indicate that a cationic

• presence of an appropriate sensitizer, such as acetone or benzophenone, dibenzobarrelene (DBB) rearranges to dibenzosemibullvalene (DBS), whereas the direct excitation leads to dibenzocyclooctene (DBC) through the singlet excited-state (Scheme 1) [4][5][7]. The DPM photorearrangement of dibenzobarrelene

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• (DMT) and 1,3-dimethyluracil (DMU) with benzophenone (1b) and some 4,4’-disubstituted derivatives (dimethoxy (1a), difluoro (1c), dichloro (1d), dibromo (1e) and dicyano benzophenone (1f)) that gives rise to two regioisomeric oxetanes, 2 and 3. The regioselectivity (the ratio of 2/3) decreased

• 1c) is enthalpy–entropy controlled. A heavy atom effect is suggested to be responsible for these unusual phenomena based on the triplet-diradical mechanism of the Paternò–Büchi reaction. Keywords: benzophenone; heavy atom effect; Paternò–Büchi reaction; regioselectivity; triplet diradical

• detected for the reaction of α-deuterated propionaldehyde [15]. In this work, we have investigated the Paternò–Büchi reaction of 1,3-dimethylthymine (DMT) and 1,3-dimethyluracil (DMU) with benzophenone (1b) and its 4,4’-disubstituted derivatives 1a and 1c–1f with the formation of the regioisomeric oxetanes

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• transfer from the aromatic moiety to the benzophenone has been previously shown by time resolved spectroscopy to result in the formation of a radical ion pair [52][53][54]. HOMO and LUMO surfaces and energy gaps Cyclic voltammograms of 1a–e and 1g were recorded in acetonitrile in order to obtain the redox

• ; ESI Q-TOF MS m/z 371 [M + H]+; HRMS calcd for C28H19O [M + H]+ 371.1436; found, 371.1433. 4-(2-Triphenylenylethynyl)benzophenone (1e). The crude product was purified by column chromatography with a mixture of hexane and dichloromethane (80:20, v/v) as eluant to yield 1e as a colorless solid (0.517 g

En route to photoaffinity labeling of the bacterial lectin FimH

• Thisbe K. Lindhorst,
• Michaela Märten,
• Andreas Fuchs and
• Stefan D. Knight

Beilstein J. Org. Chem. 2010, 6, 810–822, doi:10.3762/bjoc.6.91

• of the benzophenone 3, on the other hand, delivers a reactive triplet diradical. In addition, in order to combine a photoactive functional group with an affinity label within the same mannoside, the orthogonally protected glycoamino acid scaffold 4 was synthesized and used for the preparation of the

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• anilines but also for N-monosubstituted substrates and even those with a free NH2 group (Scheme 11). In naphthalene and benzophenone derivatives only those rings containing hydroxy or amino groups undergo perfluoroalkylsulfanylation [74][75]. Other electron-donating substituents on the aromatic ring are

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• , alkylation of a glycine enolate with the primary bromide 5 was anticipated. Indeed, its use as the electrophilic component in the coupling with the benzophenone-derived imine of tert-butyl glycine 6, which functioned, after deprotonation, as a synthetic equivalent of a glycine enolate synthon, led to the

• by using Merck TLC Silicagel 60F254 aluminium sheets. Tetrahydrofuran (THF) was freshly distilled from sodium/benzophenone under a nitrogen atmosphere, and dichloromethane was freshly distilled from calcium hydride. 7-Hydroxy-4-(2-hydroxyethyl)-2H-chromen-2-one (3): A 500 mL flask was equipped with a

Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

• Florian K. Wolf,
• Anna M. Fischer and
• Holger Frey

Beilstein J. Org. Chem. 2010, 6, No. 67, doi:10.3762/bjoc.6.67

• purified by vacuum distillation over CaH2 directly prior to use. Tetrahydrofuran (THF) was refluxed with sodium/benzophenone before distillation. Glycolide was purchased from Purac®/Gorinchem (Netherlands) and used as received. Tin(II)-2-ethylhexanoate (Sn(Oct)2), 97% was obtained from Acros and used as

Synthesis and crystallographic analysis of meso-2,3-difluoro-1,4-butanediol and meso-1,4-dibenzyloxy-2,3-difluorobutane

• Bruno Linclau,
• Leo Leung,
• Jean Nonnenmacher and
• Graham Tizzard

Beilstein J. Org. Chem. 2010, 6, No. 62, doi:10.3762/bjoc.6.62

• or anisaldehyde stains. Reaction solvents were dried before use as follows: THF and Et2O were distilled from sodium/benzophenone; CH2Cl2 and Et3N were distilled from CaH2; toluene was distilled from sodium. X-ray data crystal structure analyses: Suitable crystals were selected and data collected on a