One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Recyclable hypervalent-iodine-mediated solid-phase peptide synthesis and cyclic peptide synthesis

• Dan Liu,
• Ya-Li Guo,
• Jin Qu and
• Chi Zhang

Beilstein J. Org. Chem. 2018, 14, 1112–1119, doi:10.3762/bjoc.14.97

• , and it plays a crucial role in the elaboration and composition of biological systems. Amide bonds are widely present not only in peptides and proteins but also in pharmaceuticals and many natural products. Among the methods for amide bond formation, the direct condensation of carboxylic acids and

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• Nojihigashi, Kusatsu, Shiga 525-8577, Japan. Tel & Fax: +81-77-561-5829 10.3762/bjoc.14.94 Abstract An oxidation system comprising phenyliodine(III) diacetate (PIDA) and iodosobenzene with inorganic bromide, i.e., sodium bromide, in an organic solvent led to the direct introduction of carboxylic acids into

• benzylic C–H bonds under mild conditions. The unique radical species, generated by the homolytic cleavage of the labile I(III)–Br bond of the in situ-formed bromo-λ3-iodane, initiated benzylic carboxylation with a high degree of selectivity for the secondary benzylic position. Keywords: carboxylic acids

• synthesis of lactones via the intramolecular oxidative cyclization of aryl carboxylic acids at the benzyl carbon under transition-metal-free conditions [52]. Based on our previous research and general interest in the unique reactivity of hypervalent iodine(III)–Br bonds [53][54][55][56], we report the

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

• Kensuke Kiyokawa,
• Daichi Okumatsu and
• Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

• Kensuke Kiyokawa Daichi Okumatsu Satoshi Minakata Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan 10.3762/bjoc.14.92 Abstract The decarboxylative acetoxylation of carboxylic acids using a combination of PhI(OAc)2 and

• I2 in a CH2Cl2/AcOH mixed solvent is reported. The reaction was successfully applied to two types of carboxylic acids containing an α-quaternary and a benzylic carbon center under mild reaction conditions. The resulting acetates were readily converted into the corresponding alcohols by hydrolysis

• . Keywords: acetoxylation; carboxylic acids; decarboxylation; hypervalent iodine; iodine; Introduction The decarboxylative functionalization of carboxylic acids and the derivatives thereof is an important transformation in organic synthesis. In recent years, increasing efforts have been devoted to the

Preparation, structure, and reactivity of bicyclic benziodazole: a new hypervalent iodine heterocycle

• Akira Yoshimura,
• Michael T. Shea,
• Cody L. Makitalo,
• Melissa E. Jarvi,
• Gregory T. Rohde,
• Akio Saito,
• Mekhman S. Yusubov and
• Viktor V. Zhdankin

Beilstein J. Org. Chem. 2018, 14, 1016–1020, doi:10.3762/bjoc.14.87

• is a very stable compound with good solubility in common organic solvents. This compound can be used as an efficient reagent for oxidatively assisted coupling of carboxylic acids with alcohols or amines to afford the corresponding esters or amides in moderate yields. Keywords: benziodazole

• preparation of several bicyclic benziodoxoles 3 starting from 2-iodoisophthalic acid (2, Scheme 1b). These bicyclic benziodoxoles 3 can be used as efficient coupling reagents for the direct condensation reaction between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, or amides

• reactions. Previously, Zhang and co-workers reported the reactions of carboxylic acids with alcohols or amines in the presence of stoichiometric amounts of iodosodilactones 3 forming the corresponding esters or amides in moderate to good yields via an oxidatively assisted coupling reaction [23][24][25]. We

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• ferrocene carboxylic acids 1–4 (Scheme 2) [45][46][47][48][49][50][51][52]. The extremely bulky and electron-poor pentakis(methoxycarbonyl)cyclopentadienyl ligand gives a pseudo octahedral high-spin iron(II) complex 5, instead of forming a stable classical low-spin sandwich complex, precluding its

• ferrocene carboxylic acids 1 [45][46], 2 [47][48][49], 2a [50], 2b [51][52], 3, 4 [54] and pseudo octahedral high-spin iron(II) complex 5 with pentakis(methoxycarbonyl)cyclopentadienyl ligands [55][56]. Electrochemical data of esters 1–4 and sum of Hammett substituent constants σpa and σma. 1H NMR data (δ

2-Iodo-N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation

• Takayuki Yakura,
• Tomoya Fujiwara,
• Akihiro Yamada and
• Hisanori Nambu

Beilstein J. Org. Chem. 2018, 14, 971–978, doi:10.3762/bjoc.14.82

• reaction time than that with 13 (Table 2, entry 5). The primary alcohols 14g–k were converted into the corresponding carboxylic acids 26g–k in moderate to excellent yields (Table 2, entries 6–10). However, the reaction times of the oxidations of 14h, 14i, and 14k with 17 were similar to those involving 13

• . These results may be due to the slow oxidation of the aldehydes to carboxylic acids [69]. The catalyst 17 was stable under the oxidation conditions and it was recovered in 67–92% after reductive treatment. The next objective was to investigate the oxidation mechanism of 2-iodobenzamide catalysts

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• . LAG of a 1:1 mixture of 5FU/4-hydroxybenzoic acid using a variety of liquids yielded co-crystals exhibiting polymorphism which was dependent upon the polarity of the added liquid [84]. Co-crystals of structurally-related carboxylic acids with 5FU prepared using LAG in a MBM in the presence of water

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

• unusual, because many ethyl esters and esters derived from carboxylic acids with an odd number of carbons were found. Since the carboxylic acid portion usually derives from fatty acid biosynthesis, a process in which the C2 starter acetyl-CoA is elongated with C2 units, esters from carboxylic acids with

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• treatment with trifluoroacetic acid to provide in-situ the corresponding benzoic acids 14a–e and 15. The direct coupling of these functionalized carboxylic acids with chiral benzylic primary amines, (R) or (S)-16 (NH2-CH(Me)Ph) and (R)-17 (NH2CH(Me)p-MeO-C6H4), afforded the required parent amides 6a–d, 7a–e

Synthesis and stability of strongly acidic benzamide derivatives

• Frederik Diness,
• Niels J. Bjerrum and
• Mikael Begtrup

Beilstein J. Org. Chem. 2018, 14, 523–530, doi:10.3762/bjoc.14.38

• )benzimidamides (also termed benzamidines) have been generated, but only one report describes their syntheses [10]. The N-triflylbenzamides are stronger acids than any of the carboxylic acids, including trifluoroacetic acid (3). The N,N’-bis(triflyl)benzimidamides are very strong organic acids, much stronger than

The selective electrochemical fluorination of S-alkyl benzothioate and its derivatives

• Shunsuke Kuribayashi,
• Tomoyuki Kurioka,
• Shinsuke Inagi,
• Ho-Jung Lu,
• Biing-Jiun Uang and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2018, 14, 389–396, doi:10.3762/bjoc.14.27

• anodic oxidation of carboxylic acids 1m and 1n in the presence of a fluoride source. Electrochemical fluorination of S-butyl benzothioate derivatives. Oxidation potentials and electrochemical fluorination of S-substituted alkyl benzothioates. Supporting Information Supporting Information File 96

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• 5-aminopyrazole-4/3-ethylcarboxylates 126 with trifluoromethyl-β-diketones 17 in acetic acid under microwave heating, which were subsequently hydrolyzed to the corresponding pyrazolo[1,5-a]pyrimidine carboxylic acids 128 by treating with sodium hydroxide in ethanol at 65 °C. The compounds were

• presence of methanolic sodium hydroxide to give corresponding carboxylic acids 134. Aminobenzothiazoles 135 were linked with carboxylic acids 134 to provide the amide derivatives (benzothiazolyl derivatives, 136) using amide coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide

• )prop-2-en-1-one 162 in aqueous ethanol at ambient temperature through the intermediacy of methyl 7-heteroarylpyrazolo[1,5-a]pyrimidine-3-carboxylates 163 which was subsequently hydrolyzed to give the corresponding carboxylic acids 164 followed by coupling with various primary and secondary amines 165

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• method tolerates the presence of pyridine derivatives, alcohols, esters, carboxylic acids, Boc-protected amines, boronic pinacol esters and was applied to the late-stage functionalization of complex molecules. In 2016, the first metal-free photoredox-catalyzed radical thiol–yne reaction was reported by

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• ]nonadienes (bisdioxines) 4. When arylamines are used as the nucleophiles under neutral conditions, decarboxylation occurs during the formation of bisdioxines 8. However, when water or alcohols are added to 3 under acidic conditions, bisdioxine-carboxylic acids and esters 10 and 11 are obtained. Acid

• to the recently described acid-catalyzed decarboxylation of vinylic and aromatic carboxylic acids [33]. The amide derivatives 8 react in the same way as monoesters, forming arylaminotetraoxaadamantanes 25 (Scheme 6) [29][34]. The X-ray crystal structure of 25 (Ar = p-methoxyphenyl) has been published

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• decarboxylative trifluoromethylation of α,β-unsaturated carboxylic acids in the presence of CF3SO2Na and TBHP [82]. Various (hetero)arenes were compatible with these reaction conditions

Hydrolysis, polarity, and conformational impact of C-terminal partially fluorinated ethyl esters in peptide models

• Vladimir Kubyshkin and
• Nediljko Budisa

Beilstein J. Org. Chem. 2017, 13, 2442–2457, doi:10.3762/bjoc.13.241

• developed [53]. During the revision of this paper Peng et al. reported on esterification of carboxylic acids using 2,2-difluorodiazoethane, which was performed in a number of aprotic organic solvents, including acetonitrile [54]. Hydrolytic stability The kinetic stability of the ester linkage in the aqueous

• fluorine atoms in a partially fluorinated terminal alkyl group demonstrates a characteristic checkmark-shape [41]. B. Selective labeling of carboxylic acids (C-terminus in peptides) with 2,2-difluorodiazoethane yields 2,2-difluoroethyl esters [46]. C. Esters of N-acetylproline studied herein. Kinetics of

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• of a metallodrug, another metal-organic target The study of the chemical reactivity of bismuth and carboxylic acids, in particular salicylic acid, is quite relevant for the pharmaceutical industry, because of the large production of bismuth subsalicylate (Pepto-Bismol), an anti-acid used in the

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• prepare phosphonic acid have been reported above, others exist. In a non-exhaustive way of presentation, few of them are presented below. Barton et al. reported a procedure to prepare phosphonic acids from carboxylic acids that made use of white phosphorus (P4) [252]. First, the carboxylic acid is

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• primary and secondary alcohols to the corresponding aldehydes and ketones by mechanical processing under air. Ball milling was shown to promote the quantitative conversion of a broad set of alcohols into carbonyl compounds with no trace of an over-oxidation to carboxylic acids. The mechanochemical

• over-oxidation to the carboxylic acids. The final products could be easily separated/purified from the crude reaction mixture without using toxic organic solvents. Under mechanical activation conditions, the reactions provided better yields and proceeded faster than classical, homogeneous phase TEMPO

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

• Somaia Kamouka and
• Wesley J. Moran

Beilstein J. Org. Chem. 2017, 13, 1823–1827, doi:10.3762/bjoc.13.177

• -oxazolines, which are valuable heterocycles found in ligand scaffolds, natural products such as the leupyrrins [18][19], and potential pharmaceuticals (Figure 1) [20][21][22]. Traditional routes to this heterocycle include the dehydration of amino alcohols with carboxylic acids, however, this process

Selective enzymatic esterification of lignin model compounds in the ball mill

• Ulla Weißbach,
• Saumya Dabral,
• Laure Konnert,
• Carsten Bolm and
• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1788–1795, doi:10.3762/bjoc.13.173

• efficient for the enzyme-catalyzed selective esterification of the model compound erythro-1a, partly due to the non-reversibility of the reaction. However, isopropenyl esters of carboxylic acids are, in general, not readily available. Therefore, in order to find alternative acyl donors for the biocatalyst

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• -substituted isoquinolines at C-1, followed by reaction with iodine. Subsequent Suzuki cross-coupling of the resulting 1-iodoisoquinolines to methyl 2-(isoquinolin-1-yl)benzoates and intramolecular acylation of the corresponding carboxylic acids with Eaton’s reagent afforded five alkaloids of the

• valuable intermediates for the further conversion to the target oxoisoaporphines, and in previous protocols [7][17] the esters were typically converted into the corresponding carboxylic acids, and then cyclized using polyphosphoric acid. Previously we found that esters can directly be subjected to this

Development of a method for the synthesis of 2,4,5-trisubstituted oxazoles composed of carboxylic acid, amino acid, and boronic acid

• Kohei Yamada,
• Naoto Kamimura and
• Munetaka Kunishima

Beilstein J. Org. Chem. 2017, 13, 1478–1485, doi:10.3762/bjoc.13.146

• one-pot oxazole synthesis/Suzuki–Miyaura coupling sequence has been developed. One-pot formation of 5-(triazinyloxy)oxazoles using carboxylic acids, amino acids and a dehydrative condensing reagent, DMT-MM, followed by Ni-catalyzed Suzuki–Miyaura coupling with boronic acids provided the corresponding

• synthesis of oxazolone from carboxylic acids and amino acids using a dehydrative condensing reagent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM [19][20][21][22])[23]. Formation of 5-(triazinyloxy)oxazole is also reported to occur when an excess of DMT-MM was used. Recently

• )oxazole would provide trisubstituted oxazoles (Scheme 1b). Since many kinds of carboxylic acids, amino acids and boronic acids, which are corresponding to 2-, 4-, and 5-substituents of the oxazole, respectively, are commercially available, this method is suitable for the synthesis of a diverse variety of

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

• Jimena E. Díaz,
• Silvia Ranieri,
• Nadia Gruber and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• heterocycles. Many methods use 2-aminobenzylamine (2-ABA) that reacts with amidines, carboxylic acids, orthoformates, or aldehydes in oxidative conditions to yield N-unsubstituted dihydroquinazolines [11][16][26][27][28][29][30][31][32][33][34][35]. A different approach is based on the heterocyclization of