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

• in situ intramolecular cyclization of 5-aminopyrazole-4-caroxylate 35 with β-haloaldehydes 36 via the corresponding imine derivative was carried out in presence of Pd(PPh3)2Cl2 (1.0 mol %), Cu2O (1.0 mol %), 1,10-phenanthroline (2.0 mol %), TBAI (6 mol %), by Batra et al. [50] to generate the

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides

• Masanori Inaba,
• Tatsuya Sakai,
• Shun Shinada,
• Tsuyuka Sugiishi,
• Yuta Nishina,
• Norio Shibata and
• Hideki Amii

Beilstein J. Org. Chem. 2018, 14, 182–186, doi:10.3762/bjoc.14.12

• practical method for the synthesis of C3-perfluoroalkyl-substituted phthalides in a one-pot manner. Upon treatment of KF or triethylamine, 2-cyanobenzaldehyde reacted with (perfluoroalkyl)trimethylsilanes via nucleophilic addition and subsequent intramolecular cyclization to give perfluoroalkylphthalides in

• -cyanobenzaldehyde (2) and subsequent intramolecular cyclization. Results and Discussion The reaction procedure is very simple. A mixture of 2-cyanobenzaldehyde (2), CF3–SiMe3 (so-called Ruppert–Prakash reagent) [20][21], and a catalytic amount of KF in anhydrous DMF was stirred at room temperature for 1 h. After

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

• N2) which triggers an intramolecular cyclization reaction via a nitrogen-centred radical intermediate to form sulfonylated phenanthridines. The reaction is photocatalyzed by [Ru(bpy)3]Cl2 under irradiation with blue LEDs and proceeds smoothly for a variety of substituted vinyl azides and sulfonyl

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• shown in Figure 3. Furthermore, a six-membered ring involving the salt cation, the azlactone ring and the enolate might be involved in the addition step. Irreversible intramolecular cyclization of 4 gave 5 (for a reaction reversibility study of product 2h, see Supporting Information File 1), eventually

Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

• Jury J. Medvedev,
• Ilya V. Efimov,
• Yuri M. Shafran,
• Vitaliy V. Suslonov,
• Vasiliy A. Bakulev and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2017, 13, 2569–2576, doi:10.3762/bjoc.13.253

• catalyst, proton transfer and, finally, 1,3-shift of alkoxycarbonyl group in the intermediate imine D to produce thiophenes 3 and 5. However, this pathway seems to be less probable, since intramolecular cyclization B → C should have lower activation energy relative to intermolecular interaction of C=S

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• of the hydrogenated heterocyclic scaffold imidazo[1,5-b]pyridazine are the major advantages of the developed reaction. Intramolecular cyclization of 3-(aminomethyl)pyridazines and related compounds (route A). Conditions: i) R2COCl/Et3N [12], R2COOH/DCC [13][23], (R2CO)2O/Et3N [19]; ii) synthetic

Herpetopanone, a diterpene from Herpetosiphon aurantiacus discovered by isotope labeling

• Xinli Pan,
• Nicole Domin,
• Sebastian Schieferdecker,
• Hirokazu Kage,
• Martin Roth and
• Markus Nett

Beilstein J. Org. Chem. 2017, 13, 2458–2465, doi:10.3762/bjoc.13.242

• configuration, thereby facilitating an intramolecular cyclization to a cyclodeca-1,5-diene by electrophilic attack of the allylic carbocation onto the corresponding double bond. A 1,3-hydride shift by Wagner–Meerwein rearrangement followed by another cyclization would then give rise to an octahydronaphthalene

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• treatment of dihydroxylated amino acid ester (±)-1 with 1.5 equiv of Deoxofluor after 70 min afforded through intramolecular cyclization a compound which was identified on the basis of 2D NMR analysis as oxazoline derivative (±)-2 as the sole product in 71% yield. When the same reaction was carried out in

• cyclopentane β-amino ester (±)-6 with Deoxofluor under various conditions provided an unidentifiable mixture of products. However, the reaction of diol (±)-6 with 1.5 equiv of Deoxofluor in the presence of DBU as the base furnished aziridine derivative (±)-7 within 10 min through intramolecular cyclization via

• alcoholic groups in positions 4 and 5, oxazine derivative (±)-9 was formed as the single product through intramolecular cyclization involving the nucleophilic amide O-atom (Scheme 4). Upon treatment of diol (±)-8 with excess Deoxofluor (4 equiv), in addition to the expected fluorinated oxazine (±)-10, a

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• reagent yielded 1-azabicyclo[2.1.1]hexanes 60 as products of an intramolecular cyclization of the intermediate zwitterion 57. In all cases, these products were obtained as mixtures of cis-and trans-stereoisomers in favor of the trans-isomer [59][61]. Another class of nucleophilic reagents used for

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• intramolecular cyclization to 5-aminoisoxazoles 88, which were obtained in moderate to good yields. Following this synthetic scheme, 5-aminoisoxazoles 88 can be readily accessed from available nitroalkanes in three steps. Recently, Tanimoto and co-workers [22] reported the addition of TMSCN to a nitrosoallene

• enolates. Assembly of bicyclooctanone 14 via an intramolecular cyclization of nitrosoalkene NSA2. A general strategy for the assembly of bicyclo[2.2.1]heptanes via an intramolecular cyclization of α-chlorooxime TBS ethers 15. Stereochemistry of Michael addition to cyclic nitrosoalkene NSA3. Stereochemistry

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• demonstrate the regiochemistry of the reaction. These cascade reactions proceed first through a Michael addition of the primary amine on the enone, followed by an intramolecular cyclization by the pyridine/pyrimidine nucleus. Unfortunately, no crystal structure could be obtained for the imidazopyrimidines and

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• examples [25][26]. More recently, Zard et al. have developed a sequence of lauroyl peroxide-catalyzed radical additions of xanthate to substituted N-aryl vinyl sulfonamides and subsequent intramolecular cyclization to yield benzo-annelated γ-sultams [27]. Quite interestingly, the obtained sultams were

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• -pda failed to give the desired ortho-bis-thiocarbamoyl benzotriazole 30 after 2 hours of LAG. The isolated product was identified as benzimidazole thione 31, formed presumably by an intramolecular cyclization of the unstable bis-derivative 30 (Scheme 10a and b). Since N-thiocarbamoyl benzotriazoles

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• with the tert-butoxide radical to generate I. I then undergoes an intramolecular cyclization to form J, followed by aromatization to afford the desired compounds. Transition metal-induced oxidative dehydrogenation Since the applications of various transition metals as catalysts in C–N, C–O and C–C bond

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

• Juraj Dobiaš,
• Marek Ondruš,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2017, 13, 1350–1360, doi:10.3762/bjoc.13.132

• reaction of monosubstituted o-phenylenediamines 11a,f–i with pyruvic ethyl ester (18a) or its acid 18b and postulated that an equilibrium between Z E imines 19, 20 and enamine 21 is quickly reached and the rate-determining reaction step is a subsequent intramolecular cyclization yielding the regioisomeric

• standardized conditions: DMF, rt, 3 days (General procedure A). In all cases, the most nucleophilic amine from diamine 11 predominantly reacts with the most reactive α-carbonyl group from ester 12a to form an imine/enamine bond followed by amidic intramolecular cyclization to yield the main regioisomer of 3,4

An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks

• Sushil K. Maurya and
• Rohit Rana

Beilstein J. Org. Chem. 2017, 13, 1106–1118, doi:10.3762/bjoc.13.110

• inherent properties including stability towards acid–base hydrolysis, active participation in H-bonding, dipole–dipole and π-stacking interactions [37][64][65][66]. The reaction would then afford a range of acyclic precursors, which could then undergo the intramolecular cyclization reaction to furnish the

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

• Josef Jansa,
• Ramona Schmidt,
• Ashenafi Damtew Mamuye,
• Laura Castoldi,
• Alexander Roller,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

• -catalyst. A possible explanation for the formation of the condensation product 12 consists in intramolecular cyclization of the intermediate 4-alkynylpyrazole under the reaction conditions (Scheme 6). NMR spectroscopic investigations In Supporting Information File 1 the NMR spectroscopic data of all

Nucleophilic and electrophilic cyclization of N-alkyne-substituted pyrrole derivatives: Synthesis of pyrrolopyrazinone, pyrrolotriazinone, and pyrrolooxazinone moieties

• Işıl Yenice,
• Sinan Basceken and
• Metin Balci

Beilstein J. Org. Chem. 2017, 13, 825–834, doi:10.3762/bjoc.13.83

• to afford pyrrolotriazinone moiety 13. After completion of the nucleophilic cyclization reactions, we desired to activate the triple bond with iodine to synthesize pyrrolooxazinone derivatives via an electrophilic intramolecular cyclization reaction. For this purpose, N-alkyne-substituted methyl 1H

A practical and efficient approach to imidazo[1,2-a]pyridine-fused isoquinolines through the post-GBB transformation strategy

• Taofeng Shao,
• Zhiming Gong,
• Tianyi Su,
• Wei Hao and
• Chao Che

Beilstein J. Org. Chem. 2017, 13, 817–824, doi:10.3762/bjoc.13.82

• detected under these mild conditions. Subsequent heating of 4a in refluxing 1,4-dioxane or toluene failed to deliver the expected product 6a, even under acidic or basic conditions. Then, we turned to Ag and Au catalysts and investigated the metal-catalyzed intramolecular cyclization reaction of 4a and the

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• proceeds in a straightforward manner in cases where R is unbranched (though it does work for R = Ph). Using this method, we were able to easily generate diversely functionalized dithiane-linked para-quinols to study the intramolecular cyclization. Based on a prior report [30] demonstrating the efficacy of

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• ) electrophilic addition of I2 to the alkyne moiety of this intermediate produces the iodonium intermediate B, (iii) isomerization of iodonium B gives intermediate C and (iv) a sequential intramolecular cyclization and HI elimination of C finally affords thiazolidines 27 [88]. Seeking for a greener approach

• in this reaction [99]. 4 Miscellaneous Recently, Stevens and co-workers reported a robust protocol towards dihydrothiazoles through an Au(III)-catalyzed intramolecular cyclization of the corresponding dithiocarboimidates. Thus, the corresponding 5-alkylidene-dihydrothiazoles 58 were synthesized in

• synthesis of various nitrogen heterocycles and complex natural products. In this regard, recently an impressive increase in the number of publications on the preparation of thiazoles and their hydrogenated analogues through inter- and intramolecular cyclization of N-propargylamine derivatives appeared in

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

• Runjun Devi and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2017, 13, 571–578, doi:10.3762/bjoc.13.56

• (±)-2 is not feasible. Thus, the presence of an activating substituent (e.g., a nitro group) at the C-5 position of the benzene ring might be helpful in synthesizing molecules similar to 2 [31][32]. The failure to achieve an intramolecular cyclization of the diol via an SNAr reaction caused us to

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• unsubstituted 1-indanone (2) has been synthesized quantitatively by Nakamura, Sugimoto and Ohwada via trifluoromethanesulfonic acid (TFSA)-catalyzed intramolecular cyclization of ester 48 (Scheme 17) [36]. In 2013, Zhou and Matsuya have proposed an effective method for the preparation of 5,7-dimethoxy-1

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• −1. After one intramolecular ring is formed, there are three general options for a further radical reaction: a) Intermolecular radical propagation, b) intermolecular cyclization, and/or c) intramolecular cyclization. Assuming an incomplete conversion and judging from the remaining IR signals in the