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

• described by Yoshida et al. [26]. With electron-deficient arylaldehydes the yields are good to moderate. However, benzaldehyde itself gave less than 10% product. Under our conditions using 2 mol % D and 2 equiv H2O we obtained benzoic acid with a yield of 97%. Encouraged by this result, we carried out

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• molecules overlap. This contributes to the strong attractive interaction between them. The molecule consists of two linkages between the three aromatic fragments, giving an ortho-hydroxy benzylidene moiety, a benzoic acid ester moiety, and a biphenyl residue. The salicylidene linkage instead of the

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• (Scheme 22) [43]. Their strategy involved the reaction of salicylaldehyde (5) and unsaturated aldehyde 60 in the presence of catalytic amounts of TES-protected prolinol 64 and benzoic acid. High yields (87%) and excellent enantioselectivity (88%) of 2-phenylchromene 62 were achieved when the reaction was

• performed in 1,2-dichloroethane as the solvent. The presence of the benzoic acid additive is thought to be responsible for the increase in the enantioselectivity and higher yields of this reaction when compared to that of Govender and co-workers. It is also instructive to note that the catalyst loading for

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• observed. The ball-milling approach was applied to the (S)-BINAM-L-prolinamide (II) catalysed direct aldol reaction between ketones and aldehydes under solvent-free conditions by Najera and co-workers (Scheme 3) [33][34]. Using 5–10 mol % of II and 10–20 mol % of benzoic acid as additive, the aldol

Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

• Jian Yin,
• Steffen Eller,
• Mayeul Collot and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 2067–2071, doi:10.3762/bjoc.8.232

• was created with TentaGel resin [15][16], which swells in water, because encouraging results have been achieved previously with this resin. 4-(Chloromethyl)benzoic acid (13) served as an additional spacer [25] between 10 and TentaGel amino resin to incorporate the Zemplén cleavage site. Treatment of

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

• includes the selective reduction of nitro groups to amines in the presence of ketones (Scheme 11) [50][51], and the oxidation of benzaldehyde to benzoic acid, albeit with incredibly poor conversion [52]. The conversion of L-lysine (32) to L-pipecolinic acid (33, Scheme 12) has also been investigated by

Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• ). Soluble organic bases were also tested and failed to increase the yields (Table 1, entries 11 and 12). When benzoic acid (5a) was used as an additive, the yield was slightly improved to 77% (Table 1, entry 13). With the increase of the acidity, the yield was noticeably decreased (Table 1, entry 13 versus

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• sieves (4 Å) in the reaction (Scheme 2). Wang et al. [44] investigated the same tandem reaction of salicylaldehydes 1 and α,β-unsaturated aldehydes 2 employing TES-protected diphenylprolinol Ie as organocatalyst with high catalyst loading (30 mol %). With benzoic acid as cocatalyst and dichloroethane as

• )-diphenylpyrrolinol silyl ether (Ia) as organocatalyst and benzoic acid as cocatalyst in toluene at room temperature (Scheme 18). The protocol provides good yield and high enantioselectivity of the desired products. The yield of the reactions does not reduce appreciably when substituents are present on the aromatic

• of diphenylprolinol trimethylsilyl ether Ib as catalyst and benzoic acid as additive, provides 1,2-dihyroquinolines 53 with high yields (90%) and high ee (>99%) (Scheme 27). Various enal substituents, such as aryl, alkyl and ester groups, are readily tolerated in the reaction. However, with β-alkyl α

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• Brønsted acids as catalysts was screened for this reaction, and the best reaction efficiency in terms of yield and reaction time was achieved with benzoic acid (10 mol %). The scope of the reaction was investigated and was found to tolerate a wide variety of functional groups including nitro, nitriles

• -membered lactols, δ-hydroxypyrroles 8 were achieved as the products in good yields (Scheme 6). Later, Pan and Seidel independently extended this methodology to indolines using benzoic acid as the catalyst, conducting the reaction under reflux and microwave irradiation conditions, respectively, to generate

• explanation is the formation of azomethine ylide intermediate 11 (Scheme 8) [19][20]. The carbanion of ylide 11 is then protonated by benzoic acid, and the resulting benzoate anion supports the aromatization process. In fact, Seidel and co-workers provided the experimental evidence for the existence of

Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters

• Wen-Bin Yi,
• Xin Huang,
• Zijuan Zhang,
• Dian-Rong Zhu,
• Chun Cai and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138

• determined by chiral phase HPLC analysis on an SHIMADZU LC-20AD system. Synthesis of fluorous quinine ester C-1 Thionyl chloride (1.19 g, 10 mmol) was added to a mixture of (1H,1H,2H,2H-perfluorooctyl)benzoic acid (0.468 g, 1 mmol) and pyridine (75 mg, 1 mmol). After stirring of the mixture for 4 h at 50 °C

• , 101.4, 114.5, 118.9, 121.8, 127.0, 131.8, 141.7, 143.5, 144.8, 147.4, 149.6, 157.9, 170.0, 199.5, 200.2; ACPIMS m/z: 367.2 (M+ + 1). Synthesis of fluorous pyrrolidine ester C-6 N,N'-Dicyclohexylcarbodiimide (DCC) (0.206 g, 1 mmol) was added to a mixture of (1H,1H,2H,2H-perfluorooctyl)benzoic acid (0.468

Synthesis of diverse indole libraries on polystyrene resin – Scope and limitations of an organometallic reaction on solid supports

• Kerstin Knepper,
• Sylvia Vanderheiden and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1191–1199, doi:10.3762/bjoc.8.132

• benzoic acids on Merrifield resin: In a three-necked round-bottom flask equipped with a mechanical stirrer, 5 equiv of cesium carbonate are suspended in DMF (mL/mmol) and are stirred for 30 min at 50 °C. Next, 5 equiv of benzoic acid are added and the mixture is stirred for another 30 min. Afterwards, one

Parallel solid-phase synthesis of diaryltriazoles

• Matthias Wrobel,
• Jeffrey Aubé and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 1027–1036, doi:10.3762/bjoc.8.115

• potential inhibitors of protein–protein interactions. Results and Discussion Synthesis of azide-functionalized Wang resins Two azide-functionalized resins were prepared for the solid-phase synthesis of diaryl-triazoles. The commercially available 4-(bromomethyl)benzoic acid (5) was converted into azide 6 in

• phenyl ring of the benzoic acid as constant structural elements and the third ring consisting either of substituted benzenes, heteroarenes or a polycyclic aromatic compound. Lower product yields were obtained in this series of compounds, ranging from 21 to 63%. The lower reactivity of the aromatic azide

• of regioisomers in reaction 3. Instead of the 1,4-disubstituted triazoles obtained from copper(I) catalysis, the complex pentamethylcyclopentadienylbis(triphenylphosphine)ruthenium(II) chloride leads to 1,5-disubstituted triazole compounds [19]. 4-(Azidomethyl)benzoic acid functionalized Wang resin 7

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

• Gehad Zeyat and
• Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

• for the application in ligation studies. AMPB = (aminomethylphenylazo)benzoic acid. Structure of the glycine-linked auxiliary conjugates 7 and 8. Structural differences between the trans- and the cis-state of azopeptides with a SKV PDZ binding motif. Solid-phase synthesis of the ligation-mediating

meta-Oligoazobiphenyls – synthesis via site-selective Mills reaction and photochemical properties

• Raphael Reuter and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2012, 8, 877–883, doi:10.3762/bjoc.8.99

• ) was oxidized with potassium permanganate in a 1:1 solvent mixture of pyridine/H2O, to the corresponding benzoic acid 5. The reaction proceeded with an acceptable yield of 66%. However, the resulting highly deactivated aromatic system 5 did not react even under harsh bromination conditions with NBS in

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

• 29% of p-chlorobenzoic acid. The isolation of the benzoic acid derivative suggests that benzylic hydroxylation takes place, leading to cleavage of the unstable acetal [19][20]; however, this was not investigated further and the oxidation products were not characterised. The most interesting

Derivatives of phenyl tribromomethyl sulfone as novel compounds with potential pesticidal activity

• Krzysztof M. Borys,
• Maciej D. Korzyński and
• Zbigniew Ochal

Beilstein J. Org. Chem. 2012, 8, 259–265, doi:10.3762/bjoc.8.27

• yields. It is worth noting that we encountered significant difficulties while applying the Philips method for the cyclization of diamine 9 with benzoic acid and 4-chlorobenzoic acid. The expected benzimidazole was not formed, and only the substrates were isolated from the reaction mixture. Therefore we

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• the solvent of choice at reflux temperature (Table 1, entries 5, 6, 8–10). Similarly, various acids like trifluoroacetic acid (TFA), benzoic acid, acetic acid, benzylphosphonic acid, and O,O’-diethyl dithiophosphate were tried as catalysts but all of them failed to give the desired product. We

Laterally substituted symmetric and nonsymmetric salicylideneimine-based bent-core mesogens

• Sonja Findeisen-Tandel,
• Wolfgang Weissflog,
• Ute Baumeister,
• Gerhard Pelzl,
• H. N. Shreenivasa Murthy and
• Channabasaveshwar V. Yelamaggad

Beilstein J. Org. Chem. 2012, 8, 129–154, doi:10.3762/bjoc.8.15

• benzoic acids 2 and hydrogenolytic deprotection of the hydroxy group according to [47]. The final products OH 1a–c were obtained by esterification of the phenols 3 with 4-(4-dodecyloxy-2-hydroxybenzylideneamino)benzoic acid (4), which exhibits a liquid-crystalline phase itself (Cr 204 N 269 I) [42]. It

Synthesis and characterization of new diiodocoumarin derivatives with promising antimicrobial activities

• Hany M. Mohamed,
• Ashraf H. F. Abd EL-Wahab,
• Ahmed M. EL-Agrody,
• Ahmed H. Bedair,
• Fathy A. Eid,
• Mostafa M. Khafagy and
• Kamal A. Abd-EL-Rehem

Beilstein J. Org. Chem. 2011, 7, 1688–1696, doi:10.3762/bjoc.7.199

• ), 170 (COOH); MS m/z (% relative intensity): 533 (M+, 45), 425 (M+ – NH-C6H4-OH, 100), 341 (16), 214 (10), 171 (17), 87 (63). 2-(6,8-Diiodocoumarin-3-carboxamido)benzoic acid (10). Yellow crystals: Yield 91%; mp 315 °C; Anal. calcd for C17H9I2NO5: C, 36.37; H, 1.60; N, 2.50; found: C, 36.39; H, 36.39; N

A straightforward approach towards combined α-amino and α-hydroxy acids based on Passerini reactions

• Ameer F. Zahoor,
• Sarah Thies and
• Uli Kazmaier

Beilstein J. Org. Chem. 2011, 7, 1299–1303, doi:10.3762/bjoc.7.151

• aldehyde group. Therefore, we decided to run the reaction also under neat conditions as reported for the γ-oxo-amino acids. With acetic acid as the acidic component the yield of 6a was comparable to the previous examples. In principle, other acids such as benzoic acid or Cbz-protected glycine can be used

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

• Marco Blangetti,
• Patricia Fleming and
• Donal F. O'Shea

Beilstein J. Org. Chem. 2011, 7, 1249–1254, doi:10.3762/bjoc.7.145

• 4a and 4e, giving purified 4-methyl-2-(3-methylphenethyl)benzoic acid (6f) (Table 1, entry 6). This product is the result of oxidative hetero coupling of benzylic metalated xylene and 2-(methyl-metalated)-4-methylbenzoate. To more clearly illustrate a site selective metalation of 4e for the methyl

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• -protected lactic acid, the corresponding ketoenamides 61 and 62 were isolated in 58% yield. Reaction of lithiated methoxyallene with O-TBS-protected lactic nitrile and benzoic acid furnished 64 in high yield. Heterocyclic moieties were also well tolerated as demonstrated by the efficient reaction of 2

• and (S)-TBS-lactic nitrile (200 mg, 1.14 mmol) in anhydrous diethyl ether (5 mL) was added to the mixture. After stirring for 4 h, a solution of benzoic acid (0.84 g, 6.88 mmol) in anhydrous DMF (10 mL) was added. The mixture was stirred overnight and slowly allowed to reach r.t. The reaction was

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• proposed mechanism does not account for the formation of 2,4-disubstituted pyrrole without deuterium incorporation at the C-5 position. More information on whether a 1,2-aryl shift occurs was therefore sought using a non-labile 13C label at the aziridine carbon. 13C labelling studies 13C-Enriched benzoic

• acid was converted into imine 10 and subsequently coupled with 7 to give the aziridine 11, in four steps, as a 1:5 13C:12C mixture (Scheme 6). Two further 13C-enriched alkynyl aziridines, 14 and 15, with different substituents on the alkyne, were later prepared using the sulfonium salts 12 and 13. On

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• could also be carried out successfully in water (Scheme 4). The reduction of aqueous maleic acid proceeded quantitatively. Dehalogenation of p-chlorobenzoic acid in basic aqueous solution also proceeded smoothly and benzoic acid was obtained after acid treatment. In the case of p-chlorophenol, the

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

• of solvents and the influence of additives was undertaken [40]. It was identified that the use of a specific 23 mol % of benzoic acid significantly increased the cis/trans ratio from a base level of 55:45 to 92:8 (16 h reaction time at ambient temperature) in an overall yield of 86%. It was also