Mechanochemical synthesis of unsymmetrical salens for the preparation of Co–salen complexes and their evaluation as catalysts for the synthesis of α-aryloxy alcohols via asymmetric phenolic kinetic resolution of terminal epoxides

• Shengli Zuo,
• Shuxiang Zheng,
• Jianjun Liu and
• Ang Zuo

Beilstein J. Org. Chem. 2022, 18, 1416–1423, doi:10.3762/bjoc.18.147

• and preparation of suitable salen compounds, sometimes are described as bis-imine Schiff bases. Imines were originally synthesized by Schiff from the condensation of carbonyls with amines [25]. Thereafter, syntheses of salens were extensively reported using timely technologies [26][27][28][29

A Se···O bonding catalysis approach to the synthesis of calix[4]pyrroles

• Qingzhe Tong,
• Zhiguo Zhao and
• Yao Wang

Beilstein J. Org. Chem. 2022, 18, 325–330, doi:10.3762/bjoc.18.36

• bonding interactions between phosphonium selenides and carbonyls can significantly activate carbonyl groups [41][42][43], thus providing a new opportunity to develop carbonyl chemistry. To expand the catalysis capability of chalcogen bonding interactions, we envisioned that consecutive condensations

Glycosylated coumarins, flavonoids, lignans and phenylpropanoids from Wikstroemia nutans and their biological activities

• Meifang Wu,
• Xiangdong Su,
• Yichuang Wu,
• Yuanjing Luo,
• Ying Guo and
• Yongbo Xue

Beilstein J. Org. Chem. 2022, 18, 200–207, doi:10.3762/bjoc.18.23

• distinctive peaks for two anomeric protons at δH 5.71 (d, J = 7.7 Hz, H-1'') and 4.94 (d, J = 7.1 Hz, H-1'''), implied the co-existences of two sugar moieties. Analyses of the 13C NMR (Table 1) coupled with DEPT and HSQC spectra of 1 displayed 29 carbon signals assignable to two ester carbonyls (δC 161.3 and

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• % yield (Scheme 11) [89]. Modifications in β-carbonyls 1,2-Naphthoquinone derivatives can be obtained through modifications in the carbonyls, leading to the formation of new compounds containing different groups, such as hydroxylamines, oxiranes, hydrazones, and heterocycles. These modifications can be

• ). Other naphthoquinone derivatives were synthesized with modifications at one of the carbonyls. Tseng and co-workers [91] synthesized 4-arylamino-1,2-naphthoquinones 45a,b and 4-phenoxy-1,2-naphthoquinones 47a,b as potential anti-inflammatory agents capable of inhibiting the expression of nitric oxide (NO

• . These data indicated that 47b targets p38 kinase and NF-κB and may serve as an anti-inflammatory agent (Scheme 13). In 2020, Almeida and co-workers [92] synthesized naphthoquinone imines from β-NQSNa (18) with modifications in β-carbonyls. These compounds were obtained in a sequence of reactions

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• natural product synthesis, pigments and dyes. Different variety of α-amino carbonyls [2], α-amino acids [3] and 1,2-diamines were prepared from the nitriles using homogeneous and heterogeneous catalysis [4][5][6]. One of the astonishing aspects of nitriles is that it can be easily converted to amines

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• at 3310 and 1656 cm–1 suggested the presence of OH/NH and carbonyl groups. 1H, 13C, and HSQC spectra (Table 3) revealed the composition of this molecule to be two shielded carbonyls, five other sp2 nonprotonated carbons, five sp2 methines, one sp3 methine, two sp3 methylenes, three singlet methyls

• , and two amino protons. The remaining OH group should be a part of a carboxylic acid functionality considering the lack of oxygenated carbons besides carbonyls, and two degrees of unsaturation, not accounted for by double bonds, were consistent with the indole ring. As expected, assembling the above

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• of prolinol silyl ether (cat. 120) and benzoic acid (A1) catalysts to bring about reaction between 3-formyl-substituted indoles or pyrroles 118 and diverse electrophiles, including carbonyls, imines and other Michael acceptors (Scheme 5) [69]. The reaction with secondary amines occurred via the

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• solvent was removed under reduced pressure and the resulting crude biaryl carbonyls were purified using silica gel column chromatography (using EtOAc/hexane mixtures as eluent). Experimental details for the preparation of compounds 13a–f can be found in Supporting Information File 1. Oxime ester formation

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• dominant. Subsequent investigations by Yu expanded the scope to acyl radicals generated from carboxylic acids 56, affording enantioenriched 1,4-carbonyls 57 in excellent yields and good enantioselectivities (21 examples, up to 90:10 er) (Scheme 7b) [40]. The quantum yield was also measured to be <1 (Φ

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• more electrophilic ketone carbonyls of compounds IV firstly. To overcome these issues, we examined the reaction of acylpyruvic acid (2a) with o-aminothiophenol (1a) in the presence of carbodiimides in various solvents (Table 1). Fortunately, in many cases we succeeded to detect the desired BTA 3a by

Stereoselective Biginelli-like reaction catalyzed by a chiral phosphoric acid bearing two hydroxy groups

• Xiaoyun Hu,
• Jianxin Guo,
• Cui Wang,
• Rui Zhang and
• Victor Borovkov

Beilstein J. Org. Chem. 2020, 16, 1875–1880, doi:10.3762/bjoc.16.155

• DHPMs becomes an urgent and paramount task. In connection with this, multicomponent Biginelli and Biginelli-like reactions of aldehydes, urea/thiourea, and enolizable carbonyls revealed as very efficient tools to prepare DHPMs [3]. Although the Biginelli reaction was firstly discovered over a century

Disposable cartridge concept for the on-demand synthesis of turbo Grignards, Knochel–Hauser amides, and magnesium alkoxides

• Mateo Berton,
• Kevin Sheehan,
• Andrea Adamo and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2020, 16, 1343–1356, doi:10.3762/bjoc.16.115

• complexes to produce fluorescent species [16]; (5) sodium borohydride to reduce carbonyls [17]; (6) red phosphorous to produce polyphosphides [18]. Our initial foray into this area was born out of necessity. We wanted to conduct flow reactions that required solids, and packed beds facilitated the use of

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• -toxic and environmentally safe. These reagents play a dual role, as they enhance the electrophilicity of nitriles, carbonyls and carbinols, and can also react irreversibly with water. Unlike PPA, a Brønsted acid incompatible with some acid-sensitive functionalities, PPE and PPSE are aprotic and mild

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• further oxidation to carbonyls or carboxylates. Other reactions, such as epoxidation, ether bond formation, and structural rearrangement have also been reported (Figure 7). CYP114 in gibberellin (5) biosynthesis, for example, catalyzes the unique oxidation/six-membered to five-membered ring contraction of

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• , 4, and 6), (b) increased hydrogen-bonding-acceptor basicity which is obtained by replacing ester carbonyls with amide carbonyls (compare guest templates 7, 8 and 9), and (c) complementary distance between the two carbonyls (compare template 3 with 16). 3.2. Squaraine, thiosquaraine, croconaine, and

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• show characteristic absorbance bands at 3200–3500 cm−1 for the N–H bond stretching vibration and at 1640–1750 cm−1 for two carbonyls of the amide groups and one carbonyl of the ester group. The 1H NMR spectra of the products show a characteristic peak at 6–7 ppm for the amide hydrogen and a peak as

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

• Pedro N. Batalha,
• Luana da S. M. Forezi,
• Maria Clara R. Freitas,
• Nathalia M. de C. Tolentino,
• Ednilsom Orestes,
• José Walkimar de M. Carneiro,
• Fernanda da C. S. Boechat and
• Maria Cecília B. V. de Souza

Beilstein J. Org. Chem. 2019, 15, 388–400, doi:10.3762/bjoc.15.35

• negative charge due to the two conjugated carbonyls (C-4 and CONH) and the adjacent aromatic system. At least nine main resonance structures involved in charge dispersion can be identified for this species. The carboxamide conjugate base, on the other hand, has its charge dispersed by only two main

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• contributions have been made by synthetic chemists to search for new method for the efficient synthesis and functionalization of pyridines. Among the most significant techniques are condensation reactions between reactive carbonyls and amines (namely Hantzsch [10] and Chichibabin pyridine synthesis [11][12

• -dicarbonyl compounds, and ammonium acetate promoted by acid under aerobic conditions [37][38]. Furthermore, Brønsted- and Lewis-acid-catalyzed cyclization reactions between β-enamino esters (derived from β-ketoesters and ammonium acetate) and alkynones/α,β-unsaturated carbonyls/in situ generated α,β

Carbonylonium ions: the onium ions of the carbonyl group

• Daniel Blanco-Ania and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2018, 14, 2568–2571, doi:10.3762/bjoc.14.233

• organylated) carbonyl (1) and hydroxy (or organyloxy) carbenium ion (2): two possible representations of the same intermediate. Oxacarbenium, oxocarbenium, oxycarbenium and carboxonium ions. Acid-catalyzed interconversion of carbonyls, hydrates, hemiacetals and acetals.

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• quinolines of type 10 via C→D, the ethyl acetopyruvate has two carbonyls a and b as depicted in 13 that result in regioisomeric products upon ring closure. The desired quinoline 11 requires ring closure onto carbonyl b. To that end, ethyl sodioacetopyruvate was prepared via Claisen condensation of acetone

One-pot synthesis of epoxides from benzyl alcohols and aldehydes

• Edwin Alfonzo,
• Jesse W. L. Mendoza and
• Aaron B. Beeler

Beilstein J. Org. Chem. 2018, 14, 2308–2312, doi:10.3762/bjoc.14.205

• into carbonyls [8][9][10][11][12][13][14][15][16][17], and application to cascade or domino reactions [18][19]. More recently, our group has used benzyl epoxides for the photoredox generation of carbonyl ylides which are leveraged in the synthesis of cyclic ethers [20]. This work has led us to search

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• -catalyzed hydroarylation of C=X bonds Transition-metal-catalyzed addition of C–H bond to polar π bonds such as imines, isocyanates and carbonyls is one of the efficient methods to incorporate heteroatoms in organic molecules [45]. Yoshikai et al. developed an addition reaction of arylpyridines 3 to imines

Bi-mediated allylation of aldehydes in [bmim][Br]: a mechanistic investigation

• Mrunesh Koli,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2018, 14, 2198–2203, doi:10.3762/bjoc.14.193

• Barbier-type allylations of carbonyls have been reported in organic solvents [28][29][30], water [31] or under solvent-free conditions [32][33]. The solvent free synthetic procedure required a large excess (4–8 equiv) of Bi metal [33] whereas, the reactions in water or in organic solvents required either

• with reducing metals, e.g., Mg-BiCl3 [36], Fe-BiCl3 or Zn-BiCl3 [30], and Al-BiCl3 [37] have been used. Aqueous NH4Cl was also employed as an additive in the Al/BiCl3 mediated allylation of carbonyls in aqueous THF [38]. Results and Discussion Initially, we screened different solvents and metal

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• oxidants are employed. For example, the oxidation of alcohols to carbonyls traditionally requires strong oxidants (Cr(VI) species, IBX, DMP), whereas similar reactions using photochemical methods can utilise oxygen (O2) as the oxidising agent. The oxidising agent can accept electrons either from the

• potential to be of interest if explored further. The good physical chemical properties of thiazoles, as well as their ability to act as isosteres to thiophenes, carbonyls and pyrazoles [49][50] make this scaffold an intriguing novel motif. 2.3 C(sp2)–X bond formation The obvious extension after considering

• . Aliphatic and heteroaromatic substituents on the 2H-azirine were not tolerated. The aldehyde substituents are much more diverse, with a variety of substituted benzenes, heteroaromatics, carbonyls and aliphatic side chains undergoing the cycloaddition. Overall, these two methods provide much more mild