Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• carboxylation. The carboxylation of various propargyl acetates containing the trimethylsilyl (TMS) group as the R1 group proceeded under the optimal reaction conditions, affording the corresponding carboxylic acids 2b–e in good-to-high yields (Scheme 2). Notably, the ester and chloro functionalities in 2b and

• 2c, respectively, were compatible with the reaction conditions. For the carboxylation of tertiary-alcohol-derived acetates to the corresponding carboxylic acids 2d,e, CoI2(bpy) was found to be an effective catalyst. The yields of product 2 decreased when less bulky substituents (R1) were used. Thus

• diverse alkenyl triflates was also examined. As a result, the desired carboxylic acids 4a–k were obtained in good-to-high yields, as shown in Scheme 5. Notably, the ester and p-toluenesulfonate functionalities in 4c and 4d, respectively, were tolerated. An indole-functionalized substrate 3f was converted

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• carboxylic acids, host 1 has limited solubility in unbuffered water. Thus for solubility reasons, titrations of 1 were performed in 20 mM NaOH solution (see Supporting Information File 1, Figure S2, for more details). In each case titrations were taken to 100 mM salt where it was assumed that the host is

Cobalt-catalyzed peri-selective alkoxylation of 1-naphthylamine derivatives

• Jiao-Na Han,
• Cong Du,
• Xinju Zhu,
• Zheng-Long Wang,
• Yue Zhu,
• Zhao-Yang Chu,
• Jun-Long Niu and
• Mao-Ping Song

Beilstein J. Org. Chem. 2018, 14, 2090–2097, doi:10.3762/bjoc.14.183

• rapidly in recent years. By contrast, alkoxylation or phenoxylation confronts great challenges because alkanols or phenols are easily converted into the corresponding aldehydes, ketones, or carboxylic acids [7][23][24][25]. Recently, Gooßen [26][27], Sanford [28], Song, [29][30] and others [31][32][33][34

Artificial bioconjugates with naturally occurring linkages: the use of phosphodiester

• Takao Shoji,
• Hiroki Fukutomi,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 1946–1955, doi:10.3762/bjoc.14.169

• activated 5’-terminus without difficulty (Scheme S2, Supporting Information File 1). Furthermore, to our delight, the conjugation was compatible with carboxylic acids that are potential nucleophiles for the activated 5’-terminus and can also induce side reactions of the phosphoramidite (Scheme 1). This

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• and its efficient utilization in the spirocyclization of naphthols containing carboxylic acids. 1-Naphthol-2-propionic acids 37 were cyclized to corresponding spirolactone derivatives 39 using chiral-8,8’-diiodonaphthyl reagent 38 as precatalyst, mCPBA as an oxidant in chloroform at low temperature

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• circumstances. Keywords: anomeric stereoselectivity; carbohydrates; glycoside synthesis; Mitsunobu reaction; Introduction Fifty years ago, Oyo Mitsunobu reported a preparation of esters from alcohols and carboxylic acids supported by two auxiliary reagents, diethyl azodicarboxylate (DEAD) and

• or secondary alcohols, while the nucleophilic species needs to be acidic [13] with a pKa < 11. Otherwise the azo reagent would compete with the acidic nucleophile and participate in the substitution reaction [14]. Various compounds comply with that condition: carboxylic acids, phenols, hydrazoic acid

• stereoselective coupling of an allyl glucuronide, in which all hydroxy groups except the anomeric OH were O-acyl-protected, with carboxylic acids by a Mitsunobu reaction [35]. The reaction was successful even when a free phenolic function was present in the employed acid and the desired β-anomer of the 1-O-acyl-β

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• = COOEt); di-tert-butyl, R3 = COOt-Bu etc.) act as the most common dipolarophiles because of their high reactivity. Moreover, one or both carboxylate groups in position 3 and 4 in the final pyrazole are easily removable using a hydrolysis/decarboxylation protocol [5][16] thus giving pyrazole-4-carboxylic

• acids – potent xanthine oxidoreductase inhibitors [40] or even 3,4-unsubstituted pyrazoles [16]. Both pyrazole carboxylic groups can be also modified to hydrazides and oxazole rings [26] or a new condensed pyridazine ring [27]. Less reactive dipolarophiles such as dibenzoylacetylenes (1,4-diphenylbut-2

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