A metal-free approach for the synthesis of amides/esters with pyridinium salts of phenacyl bromides via oxidative C–C bond cleavage

• Kesari Lakshmi Manasa,
• Yellaiah Tangella,
• Namballa Hari Krishna and
• Mallika Alvala

Beilstein J. Org. Chem. 2019, 15, 1864–1871, doi:10.3762/bjoc.15.182

• of a C–C bond followed by formation of a new C–N/C–O bond in the presence of K2CO3. Various pyridinium salts of phenacyl bromides can be readily transformed into a variety of amides and esters which is an alternative method for the conventional amidation and esterification in organic synthesis. High

• intermediate A. The attack of the ortho-position of the pyridinium moiety by the nucleophilic oxygen of intermediate A is then proposed to generate cyclic oxazolopyridine intermediate B [42][43]. The intermediate B then undergoes a rearrangement to afford N-alkylated benzamide 3 via a C–C bond cleavage with

• pyridinium salts of phenacyl bromides for the construction of amides and esters in the presence of base via oxidative C–C bond cleavage. The promising features of this methodology include the absence of a metal catalyst, employing a simple inorganic base and operational simplicity for application in organic

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• triazatriangulenium ion 6 was synthesized according to a procedure of Laursen and Krebs [13]. The platform 6 was functionalized with norbornadiene 5 by deprotection of the acetylene with potassium hydroxide and in situ formation of the C–C bond between the acetylene and the central C atom of the platform 6 to yield

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• sources and are known as precursors to tropane alkaloids [59]. Together with (−)-pseudohygroline (2S,2'R)-62 they were synthesized from a common intermediate (2S,1'R)-63 prepared from the aldehyde (2R,1'R)-6 by Wittig olefination [60] and a regioselective C=C bond reduction (Scheme 17) [61]. N-Methylation

• MeBmt are rather challenging endeavor since these amino acids in addition to an E-configured C=C bond has three neighboring stereogenic centers. The starting aziridine aldehyde (2R,1'R)-6 already introduces the required configuration at C2 and the two other centers of chirality were created by the

• . Dehydration of 170 was completed in the presence of acid. Catalytic hydrogenation of the C=C bond in 171 took place preferentially (9:1) from the less hindered side to finally give (3R,5S)-168 as the hydrochloride salt. Substituted imidazolin-2-ones are of interest as potential aminoacyl-tRNA synthase

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• -catalyzed cross-coupling reactions have laid down the foundation of new C–C bond formations [50][51]. A number of Pd-catalyzed organic reactions viz., C–N coupling, amination and intramolecular amidation, cyclization, and Suzuki–Miyaura coupling [52][53][54][55] have recently been reported in the literature

• organic processes and have attracted considerable interest in this regard. Ru has efficiently catalyzed C–H activation reactions for C–C bond formation, aza-Michael reactions and many more MCRs [27][76][77]. During the writing of this review, we came through the fact that ruthenium catalysts were mostly

• –Villiger reactions, epoxidations of alkenes, intramolecular ring expansions, hydroaminations, and amination reactions and carbonyl–ene reactions for the formation of C–C bond. Scandium-catalyzed reactions represented remarkable enantioselectivities [79][80][81]. Recently the group of Rani has developed fly

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• bromotoluene 3 with TMS-protected acetylene 4 (95%). The C–C bond formation of 5 and 6 to give dibenzoyl 7 was achieved with potassium butoxide and elemental bromine (9%) according to a literature procedure [27]. The para-ethynyldiazocine 8 was obtained by reduction of both nitro groups, followed by oxidation

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• ; Michael addition; nickel complexes; nitroalkenes; Introduction Sulfones are widely used in organic synthesis, particularly, in various reactions of C–C and C=C-bond formation [1][2][3][4]. The use of sulfones in Julia–Kocienski [1] and Ramberg–Bäcklund reactions [2] made this class of compounds

• transition metal complexes. The preparation of hydroxy sulfones from β-ketosulfones in the presence of Ru [19][20], Ir [21] and Rh [22] complexes was described. Chiral sulfones were also obtained by hydrogenation of the C=C bond with α,β-unsaturated sulfones in the presence of Ir(I) complexes with P,N

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• viability of the rest of sequence outlined in Scheme 2 from an alkylated tartrate. While further C–C bond formation by enolate formation at the remaining methine on a monoalkylated tartrate acetonide had been reported by Molander and Harris [29], and by Kelly and co-workers [30]; the question whether such

Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• reaction environment. It was subsequently demonstrated how a combination of different in situ methods can provide more thorough investigation of mechanochemical reaction mechanisms [14][15][16]. Of particular benefit to synthetic reactions, such as C–C bond formation [17][18], the use of Raman spectroscopy

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• periodate, if the oxidized Dmoc in the linker were unstable, and the 2' and 3'-OH groups were exposed before sodium periodate were removed, the C–C bond between the 2' and 3' carbons could be cleaved. With the finding of the relatively high stability of the oxidized Dmoc function, we are more confident that

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• or C–C/O–C annulation at will, thus providing an easy access to annulated cyclopentanic structures III or annulated furan-based motifs IV, respectively. Additionally, in the case of C–C/C–C bond forming annulations, the products III can undergo two decarboxylation steps leading to bis-cycloalkanone

• hour) generated annulated product 4a arising from C-allylation (C–C bond forming)/intramolecular O-Michael addition (O–C bond forming) sequence. The purification of the crude reaction was easier using the Pd(OAc)2 and dppb system (Table 1, entry 2), which was thus chosen to continue the optimization

• transient η2-alkene complex A (steps a and b). Deprotonation of the pro-nucleophile 1a by the counter-anion of the η3-allyl-Pd complex exchanges the benzoate for the enolate anion (step c) [50], and following C–C bond formation from the resulting anion-scrambled complex C leads to the Pd(0) complex D (step

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• CN at 2250 cm−1. In addition, there are characteristic bands at 1664–1668 cm−1, which may include both C=C bond and the exocyclic C=N bond. Fluctuations of endocyclic C=N fragments are observed at 1584 cm−1. Thus, at least one nitrile and one NH2 group are present in the obtained compounds. The 1H

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• equatorial halogen orientation). Previous publications have already reported the C–H bond as slightly better donor than C–C bond [34][35]. Therefore, in the sum of interactions existent in the studied systems the hyperconjugation stands out, explaining the axial halogen and equatorial NH2 (ea) preference in

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• chemistry), POSS are often functionalized through the chemical processes of C=C bond transformation, e.g., hydrosilylation, Heck coupling, silylative coupling and olefin metathesis. Olefin metathesis, i.e., catalytic exchange of double bonds between carbon atoms, is a powerful tool in organic synthesis. The

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• introduced the Na2S2O8-promoted ring-opening/alkynylation of cyclopropanols 91 with ethynylbenziodoxolones (EBX) 116 for the synthesis of the alkynylated ketones 117 (Scheme 27) [107]. This reaction involved a C–C bond cleavage, radical rearrangement, and C–C bond formation, and showed a wide substrates

• 124 (Scheme 31) [111]. This transformation involved a C–C bond cleavage and two C–C bond formations, and showed excellent functional group tolerance, satisfactory yields and operational simplicity. In 2017, Mohr’s group proposed a straightforward approach to synthesize β-fluorinated ketones 114 by

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• )-2 N-Boc protection preceded the cleavage of the oxazolidine ring while silylation of the hydroxy group was necessary before oxidation of the C=C bond (Scheme 9) [58]. Further applications of the ketopinic acid framework as a chiral auxiliary relied on fine tuning of the steric environment around the

• equimolar amounts of easily separable cycloadducts 75 and 76 (Scheme 19) [81]. The bicyclic framework in the latter compound was first reduced and the hydroxy group was protected as acetate. Then the oxidative cleavage of the C=C bond gave diacid 77 (readily purified as dimethyl ester 78) which is a

• a protected serinal (R)-23 [54]. Wittig olefination extended the alkyl chain by two carbon atoms and simultaneously installed the C=C bond which was subjected to the intramolecular epoxidation to give a >20:1 mixture of aminoepoxides with the isomer (2S,3R,4R)-117 dominating. Without isolation this

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• hydrogenation of double bonds, especially for long reaction times. The ability of the Gr2 catalyst to form Ru–hydride complexes in the presence of alcohols is well-known and described in the literature [98][99]. Such complexes promoting C=C bond hydrogenation were detected in the PNB–PCOE(OH)–Gr2 system using

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• chloride ion is abstracted from 10 and binds via hydrogen bonding to the catalyst (Scheme 6) [45][47]. This leads to an ion pair [cat•Cl]− and [isoquinolinium cation]+ (Scheme 6). The nucleophilic silyl ketene acetal reacts with the [isoquinolinium cation]+ and forms the C–C bond, yielding product 12

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• catalysts (5 mol %) produced the desired product again with quite similar yields under classical conditions. However, the use of microwave or ultrasound irradiation promoted the undesired isomerisation of the C=C bond, thus lowering the yields of the desired product 9 (Table 1, entries 3 and 4). This result

Synthesis of indole–cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

• Muthumani Muthu,
• Rakkappan Vishnu Priya,
• Abdulrahman I. Almansour,
• Raju Suresh Kumar and
• Raju Ranjith Kumar

Beilstein J. Org. Chem. 2018, 14, 2907–2915, doi:10.3762/bjoc.14.269

• –C bond forming reaction [57] and three-component reactions of aromatic aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitrile and malononitrile [58][59], 2-acetylpyridine [60] or 3-amino-2-enones [61]. Incidentally, the indole scaffold is found in several natural products and bioactive synthetic compounds

• compounds. The indole–cycloalkyl[b]pyridine-3-carbonitriles comprising ortho/ortho-para/ortho-meta substituted phenyl rings exhibited axial chirality due to restricted C–C single bond rotation. Examples of biologically important cycloalkyl-fused pyridines. Axial chirality due to restricted C–C bond rotation

• received less attention. For instance, the multicomponent reactions of aldehydes, 3-(1H-indol-3-yl)-3-oxopropanenitriles and 5-aminopyrazol or naphthylamine afforded indole substituted fused pyridine derivatives [56]. 2-Indole substituted pyridine derivatives have also been prepared through AlCl3-induced C

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• amount of HPW on silica decreased the yield of reaction [62]. The silica sulfuric acid (SSA) catalyst was synthesized by the treatment of silica gel with sulfuryl chloride under room temperature stirring. The catalyst was used in the acylation of amines with 1,3-diketones via C–C bond cleavage. Various

Transition metal-free oxidative and deoxygenative C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

• Lidia A. Smyshliaeva,
• Mikhail V. Varaksin,
• Pavel A. Slepukhin,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2018, 14, 2618–2626, doi:10.3762/bjoc.14.240

• each other through the C–C bond. In order to correlate the resonance signals with the assumed structure unambiguously, two-dimensional NMR correlation 1H–13C spectra, showing direct (HSQC) and distant (HMBC) spin–spin constants, have been recorded for compound 5d (Figure 2). The presence of the cross

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• use of vitamin B12 [116]. Furthermore, cobalester, an amphiphilic vitamin B12 derivative with six ester groups and a nucleotide loop, has recently been developed to show good catalytic activity for C–C bond forming reactions [117][118]. The above-mentioned visible-light-driven system composed of 1

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• ; propellane; ring-closing metathesis; Introduction In 1966 Ginsburg coined the word “propellane” [1][2] and Wiberg reviewed various aspects of medium and small ring propellanes [3][4]. Propellanes consist of tricyclic compounds where three rings are conjoined by a common C–C bond [1][5][6]. Heterocyclic

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• (SM) cross-coupling reaction is also considered as one of the most versatile methods for C–C bond formation [8][9][10][11][12]. Application of a wide range of organometallic reagents (e.g., organoboron reagents) are possible due to their commercial availability. Owing to the mild reaction conditions

• summarized various approaches to a wide range of carbocycles and heterocycles that deals with a strategic utilization of SM coupling and metathesis as key steps. Interestingly, application of these two powerful methods in combination for a C–C bond formation process shorten the synthesis sequence for the

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

• , considerable attention has been focused on the development of the catalytic fixation of CO2 via carbon–carbon (C–C) bond formation using a variety of organic compounds as starting materials [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. A key factor for the successful catalytic fixation of CO2 is

• the carbon–metal bond formation when transition metals are used as the catalyst. In addition, the choice of suitable reducing agents is also crucial for realizing effective carboxylation reactions. In this review, the Co- and Rh-catalyzed transformations of CO2 via C–C bond-forming reactions are

• reagents in transition-metal-catalyzed C–C bond-forming reactions [21][22][23]. In particular, the carboxylation of allyl esters with CO2 has been catalyzed by Pd or Ni under electrochemical reaction conditions [24][25]. For catalytic reactions using reducing agents, Martin reported Ni-catalyzed