Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

• Tânia A. O. Fonseca,
• Matheus P. Freitas,
• Rodrigo A. Cormanich,
• Teodorico C. Ramalho,
• Cláudio F. Tormena and
• Roberto Rittner

Beilstein J. Org. Chem. 2012, 8, 112–117, doi:10.3762/bjoc.8.12

• [2]. Moreover, intramolecular HB has been found to govern the conformational preference of molecules [3]. Intramolecular HB involving halogens (X) is less common than those involving oxygen or nitrogen as proton acceptors, while fluorine when bonded to carbon hardly ever participates in HB [4]. Even

• torsional angles in degrees, and C–X distance in angstroms), and selected NBO electron delocalization (kcal mol−1) for 2'-haloflavonols. QTAIM parametersa (a.u.) and O/F/C···H/X distanceb (Å) obtained for selected interacting atoms. QTAIM parameters (a.u.) for the hydrogen involved in HB and the halogens

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• substrate range of the catalytic fluorination and its extension to other activated carbonyl compounds [57]. Results and Discussion Lewis acid catalyzed halogenation of activated carbonyl compounds Overview Nonfunctionalized ketones are halogenated in the α-position by halogens and other electrophilic

Combined directed ortho-zincation and palladium-catalyzed strategies: Synthesis of 4,n-dimethoxy-substituted benzo[b]furans

• Verónica Guilarte,
• M. Pilar Castroviejo,
• Estela Álvarez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 1255–1260, doi:10.3762/bjoc.7.146

• superbases and introduced by Schlosser [7]), as well as lithium dialkylamides, have usually been employed to perform deprotonative metallations. Whereas the use of these strong bases has several limitations regarding the presence of certain functional groups (mainly carboxylic acid derivatives and halogens

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• . reported a general gold-catalyzed direct oxidative homo-coupling of non-activated arenes 207 (Scheme 38). The reaction protocol tolerates a wide range of functional groups [92]. All halogens survive the reaction, which provides the potential for further reactions. 4.2 Rearrangements and ring enlargement A

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• reaction to prepare the C14 diketone 60 (Scheme 11). In principle, one could incorporate bridgehead halogens as in 61 with the aim of carrying out two Favorskii ring contractions to generate the octahedrane skeleton, viz. the dicarboxylic acid 62, which ultimately would then require to be decarboxylated to

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

• not so activating for reaction with CF3SCl. For example, thiophenol [76] forms only phenyltrifluoromethyl disulfide [70]. The presence of a methyl group and halogens requires high temperatures (100–200 °C) and the presence of catalysts (HF or BF3) for reaction and yields of the corresponding

• these conditions. Thus, this method allows the selective substitution of different halogens by varying the temperature. Since the original work on trifluoromethylthiocopper and trifluoromethylthiomercury [93][95][96][101][102], other nucleophilic reagents and new methods have been developed. For example

• these reactions are illustrated in Scheme 34. This reagent can displace a range of activated halides, particularly bromides and iodides. For the reaction of 2,4-(NO2)2C6H3X with AgSCF3/KI, the reactivity of the halogens occurs in the reverse sequence: F (26%) < Cl (52%) < Br (85%) < I (97%) [118

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

• Guangming Nan,
• Fang Ren and
• Meiming Luo

Beilstein J. Org. Chem. 2010, 6, No. 70, doi:10.3762/bjoc.6.70

• biaryl products. Electron-donating groups on the 1-aryltriazenes and electron-withdrawing substituents on the arylboronic acids lead to reduced yields. Steric hindrance of ortho substituents slightly reduced the product yields (Table 5, entries 4, 7). Halogens on 1-aryltriazenes gave lower yields (Table

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• , chemical and biological properties [3]. The specific physical and chemical properties of fluorine in fluorine containing compounds, especially its strong electronegativity, lipophilicity and reaction ability, differ dramatically from those of other halogens and thus lead to changes in the interaction

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• due to electrostatic effects, but polarization, charge-transfer, and dispersion contributions all play an important role, more recently confirmed also by theoretical and experimental studies [8][9][10]. Interactions between halogens and nucleophilic atoms were generally considered to be too weak to be

Solvent-free phase-vanishing reactions with PTFE (Teflon^®) as a phase screen

• Kevin Pels and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75

• and either acrylic acid or dimethyl fumarate react at a relatively high rate [26]. As most Diels-Alder reactions are relatively slow, and most dienes are highly reactive towards halogens, it may be necessary to carry out sequential reactions. Solvent-free PV-PTFE reaction design is simple and

Chemoselective reduction of aldehydes by ruthenium trichloride and resin- bound formates

• Basudeb Basu,
• Bablee Mandal,
• Sajal Das,
• Pralay Das and
• Ashis K. Nanda

Beilstein J. Org. Chem. 2008, 4, No. 53, doi:10.3762/bjoc.4.53

• such as halogens, nitro etc. were not affected under the reaction conditions (Table 2, entries 6–11, 17). Aliphatic aldehydes (Table 2, entries 14, 15) were also reduced to corresponding alcohols efficiently. Furthermore, the presence of ortho-substituents did not hinder the rate of the reduction as

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• in water more than in organic solvents (such as 1-octanol or chloroform) and hence lowers the lipophilicity [51]. It appears that the OCF3 substituent is far more lipophilic (π = +1.04) than the halogens and lies between a CF3 (π = +0.88) and a SCF3 (π = +1.44) group. It may thus replace