Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• %) efficiently catalyzed the intramolecular cyclization with 65–92% yields (Table 1, entries 3–7). To our delight, the transformation also reached 92% yield by employing 1a at 0.5 mol % (Table 1, entry 4). Compared to literature [60][61][62], catalyst 1a is effective for the tandem cyclization of 2

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• and Research, Pune, Pune 411008, India 10.3762/bjoc.15.234 Abstract The intramolecular cyclization of a C-3-tetrasubstituted furanoid sugar amino acid-derived linear tetrapeptide afforded an oxazolone pseudo-peptide with the formation of an oxazole ring at the C-terminus. A conformational study of

• interaction. However, the role of the neighboring amido groups cannot be ruled out. Moreover, the hydrophobic outer surface of the transporter helps the anion bound complex to permeate efficiently through the lipid bilayer membranes. Conclusion In conclusion, the intramolecular cyclization of linear di- and

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• -catalysed intramolecular tandem stannylation/biaryl coupling protocol gave the attempted pentacyclic products [32]. However, having the biaryls 20a and 20b prepared we intended to develop a new approach to pyrido[4,3,2-mn]acridines by an alternative intramolecular cyclization step. To reach that aim, the

Synthesis of acremines A, B and F and studies on the bisacremines

• Nils Winter and
• Dirk Trauner

Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219

• intramolecular cyclization of 23. Attempted photochemical cyclization of 25. Representative screening conditions for the biomimetic cascade. Supporting Information Experimental procedures, spectroscopic data and copies of NMR spectra (PDF) as well as crystallographic data of compounds 16 and 17. CIF files for

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• 7c. 1,3-Dipolar cycloaddition of nitrones to alkenes is known to be reversible [13][14]. We recently reported a similar reversibility of the intramolecular cyclization of sterically hindered pent-4-enylnitrone of the 2H-imidazole series [15]. Treatment with Zn in an AcOH/EtOH/EDTA/Na2 mixture was

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• have been reported so far (Scheme 1). Zeni et al. reported the synthesis of imidazoselenoazole using a three-step one-pot reaction of N-alkynylimidazoles with selenium involving the electrophilic intramolecular cyclization of acetylenic compounds (Scheme 1, reaction 1) [6]. Zeni et al. also developed a

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

• addition with a subsequent intramolecular cyclization catalyzed by Cu(BDC)MOF. Further, the LC–MS study of the reaction mixture has shown the imine formation to be the major pathway rather than β-nitrostyrene. The reaction involved a two-step reaction mechanism in which aza-Michael adduct 13 was formed in

• mechanisms, i.e., a Chan–Lam coupling and an Ullmann coupling. The Chan–Lam coupling involved a C–N bond formation (intermediate I, 84) which then entered into the Ullmann coupling to undergo intramolecular cyclization to form final product 78 and release Cu(III) to Cu(I) by reductive elimination. In this

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• =)P–CR=C=CMe2, X = Cl, OMe, NR2, or SAr] undergo intramolecular cyclization into the corresponding 1,2-oxaphospholium ions in the Brønsted superacid TfOH. These cations have been thoroughly studied by means of NMR spectroscopy. The hydrolysis of superacidic solutions of these species afforded cyclic

• (Figure 3, Table 2). Despite solvation in the Brønsted superacid TfOH, the P=O group takes part in intramolecular cyclization into oxaphospholium ions (Table 1). These two different types of reaction intermediates, generated from such allenes in Brønsted and Lewis acids, lead to various reaction products

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• excellent yields. The proposed mechanism begins with the formation of the β-aminoketoimine by condensation of the steroid with two molecules of ammonia, followed by the reaction with arylaldehyde and intramolecular cyclization to a dihydropyrimidine skeleton, which suffers oxidation to the aromatic

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• start with the formation of an imine intermediate between the aldehyde function of 33 and the amine 2, followed by a nucleophilic attack by the diketone and a final intramolecular cyclization, the Han group proposes a different pathway, with an initial deprotonation of ketoacid 34 (R2 = Me, Ar, R3 = OH

• of the reactive aryne 80 which is first trapped with the nucleophilic isocyanide to form 81 and then with the electrophilic CO2 (78), to furnish an intermediate benzoic acid derivative 82. Intramolecular cyclization would produce the corresponding isobenzofurane 83, which alternatively, could also be

• involving a sequential enamine formation-Michael addition to produce intermediate 139, followed by intramolecular cyclization to 141 and aromatization through species 142 and 143 (Scheme 40). The cyclization step takes place in a regioselective manner, leading to five-membered heterocycle 141 rather than to

SO₂F₂-mediated transformation of 2'-hydroxyacetophenones to benzo-oxetes

• Revathi Lekkala,
• Ravindar Lekkala,
• Balakrishna Moku,
• K. P. Rakesh and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 976–980, doi:10.3762/bjoc.15.95

• C, which finally undergoes an intramolecular cyclization furnishing the corresponding benzo-oxete 2. The second mechanism starts with the elimination of the proton from the acetyl group next to the carbonyl moiety of the 2'-hydroxyacetophenone 1 in the presence of the base to afford enol

• intermediate I. The latter then reacts with SO2F2 to give intermediate II and fluoride anion. The subsequent deprotonation of intermediate B by the base generates phenol anion III, which finally undergoes an intramolecular cyclization to give the corresponding benzo-oxete 2. Conclusion We have developed a new

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• alkynylation/cyclization reaction between 2-iodophenol and (triethoxysilyl)alkynes [20]. In recent years silver and gold salts have found application as versatile and mild catalysts to access the benzo[b]furan ring system through intramolecular cyclization of 2-alkynylphenol substrates [21], including

• synthetic methods has been developed for the construction of carbon–heteroatom bonds using these types of catalysts. For example, the gold(I) catalyst [(Ph3PAu)3O]BF4 was applied in the regioselective intramolecular cyclization of alkynols to construct bicyclic ethers [37], while the silver(I) catalyst

• AgOTf efficiently catalyzed the intramolecular cyclization of phenoxyethynyl diols into 2,3-unsaturated lactones [38]. In our case, the addition of 10 mol % chloro(triphenylphosphine)gold(I) improved the yield of product 4a to 69% (Table 1, entry 4). However the best results were obtained when AgOTf was

Annulation of 1H-pyrrole-2,3-diones by thioacetamide: an approach to 5-azaisatins

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

Beilstein J. Org. Chem. 2019, 15, 364–370, doi:10.3762/bjoc.15.32

• to substitute the S atom and form adduct A. Adduct A underwent a decomposition by releasing a molecule of compound 2 [18]. The formed compound B underwent intramolecular cyclization followed by hydrolysis of the imide group with subsequent decarboxylation and formation of the intermediate C that was

Reusable and highly enantioselective water-soluble Ru(II)-Amm-Pheox catalyst for intramolecular cyclopropanation of diazo compounds

• Hamada S. A. Mandour,
• Yoko Nakagawa,
• Masaya Tone,
• Hayato Inoue,
• Nansalmaa Otog,
• Ikuhide Fujisawa,
• Soda Chanthamath and
• Seiji Iwasa

Beilstein J. Org. Chem. 2019, 15, 357–363, doi:10.3762/bjoc.15.31

• 5 h (Table 2, entry 1). On the other hand, hydroxymethyl Ru(II)-Pheox (cat. 3), which is completely soluble in water, catalyzed the cyclization of 1f affording chiral cyclopropylamide 2f in 97% yield with a high enantioselectivity of 96% in 5 h (Table 2, entry 5) [49]. Next, the intramolecular

• cyclization of trans-allylic diazo Weinreb amide 1f catalyzed by Ru(II)-Amm-Pheox (cat. 2) was examined in various solvents, as shown in Table S1 (Supporting Information File 1). Notably, the catalytic reaction proceeded in a variety of solvents, including aromatic, aliphatic, polar, non-polar, and

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

• of MCPs 1 formed the more stable benzyl radical intermediate 5 [45][46], which underwent a ring-opening to generate the alkyl radical 6 [47]. Finally, the desired product 3 was generated through intramolecular cyclization of radical intermediate 6 with an aryl ring and oxidation deprotonation by

• synthesis of 1-naphthaldehydes 25 under mild conditions via a radical-mediated ring-opening and intramolecular cyclization of MCPs 23 with organic selenium reagents 24 (Scheme 8) [59]. In this reaction, the MCPs with electron-withdrawing groups gave lower yields than that with electron-donating groups

• , phenylselenyl radical 26 was produced in the presence of free radical initiator (NH4)2S2O8 [60][61]. Next, the intermediate 26 was added to the C–C double bond of MCPs 23, and then went through a series of ring-opening, intramolecular cyclization, oxidation and dehydrogenation to generate 3

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

• . However, when the reaction mixture was warmed to 0 °C before quenching, an intramolecular cyclization occurred under basic conditions to give the oxazolidine (4S,5R)-25 as an almost (>20:1) pure diastereoisomer. The hydroxy group which acted as a nucleophile preferred to attack the re-face of the double

• compound underwent another intramolecular cyclization in the 5-exo mode to form the oxazolidinone 118. To complete the synthesis of (2S,3S,4S)-4 the secondary hydroxy group was protected as a pivalate, the hydroxymethyl fragment was oxidized after hydrolysis of the silyl ether and finally all protecting

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• single crystal X-ray diffraction study (Figure 2). The sequential domino reaction presumably starts with the Knoevenagel condensation of o-hydroxybenzaldehyde and N-(cyanomethyl)pyridinium salt forming styryl derivative A, which undergoes intramolecular cyclization to give 2-iminochromene salt 3

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

• exclusively, which is evident from the fact that the decahydrocyclododeca[b]pyridin-2-amine 13 anticipated through the intramolecular cyclization of the amino group and the CN in intermediate 10 was not formed in the reaction (Scheme 2). This one-pot four-component strategy was then employed to synthesize

• –cycloalkyl[b]pyridine-3-carbonitrile hybrid heterocycles have been achieved through a facile one-pot four-component strategy. This reaction occurred through a six-step tandem Hantzsch-like process involving Knoevenagel–Michael–nucleophilic addition–intramolecular cyclization–elimination–oxidative

• formation of (E)-3-(4-chlorophenyl)-2-(1H-indole-3-carbonyl)acrylonitrile (8). Simultaneously, the reaction of cyclododecanone (5a) with ammonium acetate affords the enamine 9. The Michael addition of 8 and the enamine 9 yields the intermediate 10. Then the amino group of 10 undergoes intramolecular

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• , entry 2) shows that the intramolecular cyclization to the ortho-carbon of phenyl ring occurs, most probably, through cation C (Scheme 2). And this reaction has a high activation barrier, analogously to the similar cyclization of phosphonoallenes to the corresponding phosphonoheterocycles [30]. We

• , the atomic coefficient of contribution in the LUMO for sulfur is much higher than for C5. Thus, the electrophilic reactivity of sulfur may be explained by both charge and orbital control. Also, ortho-carbons in the phenyl group bear a negative charge −0.17 to −0.16 e; this means that intramolecular

• cyclization on these atoms is possible. To conclude the study on electronic characteristics of 1,2-oxathiolylium ions A, B by means of NMR and DFT calculations, one should expect that these species may react in several pathways. First, they may undergo nucleophilic attack on sulfur or on carbon C5, due to a

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• afforded trans-azepines 11d and 12d via intramolecular cyclization. The same procedure applied to the bulky N-(3-methylbut-2-enyl) derivatives 4e and 6e yielded the corresponding diols 9e and 10e. Whether the Pummerer reactions yielded cyclised products or not was strongly affected by the substituent

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• ], via intramolecular cyclization of a diazomethane group and a nitrile [23], or via our recently reported NH-triazole synthesis starting from 6-methoxyflavanone [24]. Furthermore, 1,4,5-trisubstituted 1,2,3-triazole annulated chromenes have been reported via an intramolecular arylation reaction of 1,2,3

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

• synthesis method through the one-pot acylation of ethyl acetoacetate with isatoic anhydrides followed by dehydrative intramolecular cyclization to access the desired quinoline scaffold 10 [18]. We replaced sodium hydride as the base required to generate the enolate of ethyl acetoacetate with sodium

Nucleoside macrocycles formed by intramolecular click reaction: efficient cyclization of pyrimidine nucleosides decorated with 5'-azido residues and 5-octadiynyl side chains

• Jiang Liu,
• Peter Leonard,
• Sebastian L. Müller,
• Constantin Daniliuc and
• Frank Seela

Beilstein J. Org. Chem. 2018, 14, 2404–2410, doi:10.3762/bjoc.14.217

• intramolecular cyclization to a macrocycle was not observed. Next, the 5’-azido compound 2 was employed in the copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) "click" reaction [38][39] to build up macrocycle 3. In this regard, two reaction pathways have to be considered: (i) an intramolecular “click

• ) sulfate and ascorbic acid. TLC monitoring showed that the cyclization failed. Then, tris(benzyltriazoylmethyl)amine (TBTA) [40][41][42] was added as catalyst and macrocycle 4 was formed in 71% yield, which is extremely high for an intramolecular cyclization. The dimeric product 3 and the cyclic dimer 5

• derivative 4 the dU macrocycle 8 could be isolated in 46% yield even in the absence of TBTA. However, the yield of cyclization was significantly improved when TBTA was added (69%). This demonstrates the influence of the nucleobase on the intramolecular cyclization reaction. All compounds were characterized

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• –Plattner rule [41][42]. Intramolecular cyclization of intermediates 12 and 13 creates the oxazolines 10 and 11. With this model at hand the β:α ratios of entries 1 to 5 in Table 1 can be explained. For R1 = Bn the equilibrium between 9a and 9b is positioned far in favor to 9a. Nucleophilic attack of the

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• was used as a stoichiometric oxidant [45]. In contrast to the intramolecular cyclization, the intermolecular reaction is much more attractive. Li and co-workers reported a syn-diacetoxylation of alkenes, using iodoarenes as catalyst which was oxidized to hypervalent iodine(III) by hydrogen peroxide in