Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• /bjoc.12.32 Abstract An oxidative reaction for the synthesis of 4-alkyl-substituted dihydroisoquinolin-1(2H)-ones with N-allylbenzamide derivatives as starting materials has been developed. The radical alkylarylation reaction proceeds through a sequence of alkylation and intramolecular cyclization. The

• . Intermediate C proceeds through intramolecular cyclization to give intermediate D. Finally, H-atom abstraction occurs between D and TBPB directly, which gives the product 5aa and regenerates radical A for the next cycle. Conclusion In summary, a metal-free cascade functionalization of unactivated C(sp3)–H

• bonds and cyclization reactions of N-substituted allylbenzamides were developed. The reaction involved cleavage of the C(sp3)–H bond, alkylation and intramolecular cyclization, affording the 4-alkyl-substituted dihydroisoquinolin-1(2H)-one derivatives with moderate to good chemical yield. The

Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

• Yan Li,
• Xue Zhou,
• Guangfan Zheng and
• Qian Zhang

Beilstein J. Org. Chem. 2015, 11, 2721–2726, doi:10.3762/bjoc.11.293

• also been widely used as chiral ligands and auxiliaries in asymmetric synthesis [3]. Therefore, the development of a new aminooxygenation reaction is still highly attractive [4]. Most of the existing aminooxygenation reactions involve an intramolecular cyclization step [5][6][7][8][9][10][11][12][13

Recent developments in copper-catalyzed radical alkylations of electron-rich π-systems

• Kirk W. Shimkin and
• Donald A. Watson

Beilstein J. Org. Chem. 2015, 11, 2278–2288, doi:10.3762/bjoc.11.248

• used extensively in polymer chemistry because of the ability of alkyl radicals to participate in chain reactions [2][3][4]. They have also been used extensively in small molecule synthesis, particularly in an intramolecular cyclization setting [5][6][7][8][9]. However, while the ability of alkyl

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines

• Mingxing Liu,
• Jiarong Li,
• Hongxin Chai,
• Kai Zhang,
• Deli Yang,
• Qi Zhang and
• Daxin Shi

Beilstein J. Org. Chem. 2015, 11, 2125–2131, doi:10.3762/bjoc.11.229

• intramolecular cyclization. Finally, 10 is oxidized to give pyrazolo[3,4-d]pyrimidine 5. Another route is that 7 undergoes an intramolecular Pinner reaction to form 11. Then 11 rearranges to dihydropyrazolo[3,4-d]pyrimidin-4-ones 13 via Dimroth rearrangement and 13 is oxidized to provide 14 [49]. Finally, 14

A new approach to ferrocene derived alkenes via copper-catalyzed olefination

• Vasily M. Muzalevskiy,
• Aleksei V. Shastin,
• Alexandra D. Demidovich,
• Namiq G. Shikhaliev,
• Abel M. Magerramov,
• Victor N. Khrustalev,
• Rustem D. Rakhimov,
• Sergey Z. Vatsadze and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2015, 11, 2072–2078, doi:10.3762/bjoc.11.223

• we assume that the radical-ions formed after the first electron transfer would enter the intramolecular cyclization reaction involving the second adjacent double bond with subsequent electropolymerization. The latter is confirmed by a pronounced decrease in current values (3–4 times) as compared to

Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

• Cesar Garcias-Morales,
• David Ortegón-Reyna and
• Armando Ariza-Castolo

Beilstein J. Org. Chem. 2015, 11, 1973–1984, doi:10.3762/bjoc.11.213

• of aldehyde to form a second aldimine. Finally, 6-endo-enol-endo intramolecular cyclization leads to piperidone formation (Scheme 2) [58][59]. Structural and conformational analysis of piperidones 1–8 by NMR and X-ray diffraction Solution characterization of 1–8 was performed by 1H and 13C NMR, and

Cross metathesis of unsaturated epoxides for the synthesis of polyfunctional building blocks

• Meriem K. Abderrezak,
• Kristýna Šichová,
• Nancy Dominguez-Boblett,
• Antoine Dupé,
• Zahia Kabouche,
• Christian Bruneau and
• Cédric Fischmeister

Beilstein J. Org. Chem. 2015, 11, 1876–1880, doi:10.3762/bjoc.11.201

• by intramolecular trans-esterification from 6, 7 and 8, as well as cyclic amines by intramolecular cyclization involving primary amine resulting from hydrogenation of the nitrile functionality in 5. All these aspects will be further developed in our group. Cross metathesis of 1 with methyl acrylate

Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

• Biljana M. Šmit,
• Radoslav Z. Pavlović,
• Dejan A. Milenković and
• Zoran S. Marković

Beilstein J. Org. Chem. 2015, 11, 1865–1875, doi:10.3762/bjoc.11.200

• addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of

• Figure 4). These intermediates are actually the reactant complexes for intramolecular cyclization. The fourth step of the proposed mechanism is a ring forming reaction which is achieved through an anti-attack of the internal nucleophile, amidic nitrogen N(1) at carbon C(5) or C(6) yielding the five

• is favored. These intermediates are readily converted into the more stable cyclic seleniranium cations. The key step is a selenium-induced intramolecular cyclization which is accomplished through an anti-attack of the internal nucleophile, amidic nitrogen, to the seleniranium cation yielding the

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• configuration) and 6i in 16:31:28:25 GC–MS ratio. The presence of these products can be explained only by the formation of the substituted SF5-phenyl radical which undergoes borylation to 2i, hydrogen atom transfer followed by borylation to 2i’, intramolecular cyclization to 5i or hydrogen abstraction to 6i

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• bearing two different olefin units one being an α,β-unsaturated moiety, the tandem CM–IMDAR protocol would initiate on the electronically neutral olefin. Furthermore, those dienes could undergo an intramolecular cyclization (RCM) promoted by the ruthenium carbene that would compete with the desired

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• alkenyl chain of sufficient length the [n]paracyclophane 172 was obtained by an intramolecular cyclization (Scheme 27). Alcaide and co-workers [153] have reported the synthesis of different bis(dihydrofuryl)cyclophane scaffolds 179 from carbonyl compounds. 1,4-Bis(3-bromoprop-1-ynyl)benzene (175) was

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• molybdenum(VI)-catalyzed etherification of allylic alcohol with a gold(I)-catalyzed intramolecular cyclization process [5][6]. During the optimization process of this synthesis, we examined several catalysts to transform allylic alcohol 1 into ether 2, including Re2O7, which is described to efficiently

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• . reported the base-catalyzed intramolecular cyclization of alkynyl alcohols at high temperatures to give 1,4-oxaza heterocycles [32]. In this manuscript we envisaged a synthetic strategy leading to the core skeleton of marine products 6 and 7 (Figure 2) or their analogues with short reaction times and an

• atom-economic process using a gold-catalyzed alkyne cyclization reaction as the key step. Pyrrole and indole, bearing one (substituted) propargyl and carboxy group was initially designed as model substrate for the construction of 6 and 7. Gold-catalyzed intramolecular cyclization of enyene carboxylic

Novel stereocontrolled syntheses of tashiromine and epitashiromine

• Loránd Kiss,
• Enikő Forró and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2015, 11, 596–603, doi:10.3762/bjoc.11.66

• intramolecular cyclization of a chiral alkenylated pyrrolidinone, followed by hydroxylation [32], or by the intramolecular ring closure of chiral pyrrolidine diesters followed by ester and oxo group reduction [33], while the syntheses of (+)-epitashiromine starts from a chiral morpholine derivative, with nitrone

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 437–445, doi:10.3762/bjoc.11.50

• reorient itself to place the remaining OH function close to the remaining NCO moiety. The subsequent intermolecular pathway is much more likely than the intramolecular cyclization to 29. Conclusion Having developed different, mostly high-yielding routes to various diamino[2.2]paracyclophanes and related

Direct access to pyrido/pyrrolo[2,1-b]quinazolin-9(1H)-ones through silver-mediated intramolecular alkyne hydroamination reactions

• Hengshuai Wang,
• Shengchao Jiao,
• Kerong Chen,
• Xu Zhang,
• Linxiang Zhao,
• Dan Liu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 416–424, doi:10.3762/bjoc.11.47

• cyclization reaction, and the expected products 9A–L were obtained in good to excellent yields (80–93%, Table 3, entries 1–12). Based on the results of the present studies, we propose a plausible mechanism for the transformation. As depicted in Scheme 2, the intramolecular cyclization is initiated by the

• ]quinazolin-9(1H)-ones 9A–L could be generated by the treatment of substituted 2-(3-butynyl)-4(3H)-quinazolinones 8A–L with AgOTf under the optimized reaction conditions. As illustrated in Table 3, 2-(3-butynyl)-4(3H)-quinazolinones 8A–L with different substituents were well-tolerated in this intramolecular

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• ]pyridine 5a or through nucleophilic substitution involving the phenolic hydroxy group under ultrasonic activation furnishing the oxygen-bridged compound 6a. Most likely, here the key influence of ultrasound is the transfer of energy to the reaction mixture that is required for intramolecular cyclization

A one-pot multistep cyclization yielding thiadiazoloimidazole derivatives

• Debabrata Samanta,
• Anup Rana,
• Jan W. Bats and
• Michael Schmittel

Beilstein J. Org. Chem. 2014, 10, 2989–2996, doi:10.3762/bjoc.10.317

• is almost impossible, we had a look at the computed energetics of the intramolecular cyclization steps to check whether our suggestion would at least comply with a reaction cascade proceeding at room temperature. To obtain the energy for the first cyclization step (Scheme 2), we performed DFT

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• subsequently the intermediate underwent intramolecular cyclization and oxidative aromatization to form the phenanthridine ring. Bowman et al. [16] modified this route for safety reasons by application of di(tert-butyl)peroxide as a source of the t-BuO• radical (Scheme 3). The required arylimines were prepared

• photoinitiation in the presence of excess t-BuOK. The photoinduced ET to the amide-anion resulted in its radical anion. After fragmentation of the C–I bond, an intramolecular cyclization occurred, and after acidification of the reaction medium, the oxidized phenanthridine compounds were obtained in very good

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• mechanism shown in Scheme 6. The sequence starts with electron transfer from cathodically generated [Ni(tmc)]+ to 12, triggering the cleavage of the C–Br bond in the rate-determining step and resulting in radical species 15. After rapid intramolecular cyclization, followed by hydrogen atom abstraction from

• number of 2-aryl-1,3-oxazolidines and 2-aryl-1,3-oxazinanes. An intriguing example for the intramolecular cyclization of alkoxycarbenium species has been reported recently by Suga, Yoshida et al. [56]. Unsaturated thioacetals 31 were converted anodically to 2,4-substituted tetrahydropyrans 32 using a

• out using Bu4NB(C6F5)4 as supporting electrolyte. 1.4 Further intramolecular cyclization reactions As a part of their efforts in the total synthesis of several natural products, Nishiyama and co-workers developed an electrochemical method for the construction of N-heterocyclic cores (see examples

Synthesis and characterization of a hyper-branched water-soluble β-cyclodextrin polymer

• Francesco Trotta,
• Fabrizio Caldera,
• Roberta Cavalli,
• Andrea Mele,
• Carlo Punta,
• Lucio Melone,
• Franca Castiglione,
• Barbara Rossi,
• Monica Ferro,
• Vincenza Crupi,
• Domenico Majolino,
• Valentina Venuti and
• Dominique Scalarone

Beilstein J. Org. Chem. 2014, 10, 2586–2593, doi:10.3762/bjoc.10.271

• from the predictable one mainly because of the different reactivity of functional groups. Moreover, Flory’s theory does not take into account either the influence of the amount of solvent (critical dilution) or the frequency of intramolecular cyclization. Different models have been developed to predict

(CF₃CO)₂O/CF₃SO₃H-mediated synthesis of 1,3-diketones from carboxylic acids and aromatic ketones

• JungKeun Kim,
• Elvira Shokova,
• Victor Tafeenko and
• Vladimir Kovalev

Beilstein J. Org. Chem. 2014, 10, 2270–2278, doi:10.3762/bjoc.10.236

• (2а), which was initially formed as the result of an intramolecular cyclization of 1a, underwent a further acylation with the formation of 1,3-diketone 3a. In contrast, γ-phenylbutanoic acid (1c) was quantitatively transformed only to the tetralone 2с (Table 1, entries 10 and 11). The acid-catalyzed

• diketone 3h (Table 2, entry 6) was also obtained by a two-stage one-pot approach, i.e., the intramolecular cyclization of the acid 1c (to form the tetralone 2c) and the following acylation with 1-adamantylacetic acid (1d) (Scheme 1). The acylation of the methyl benzyl ketone (2k) by 1-adamantylacetic acid

• for 2a and 2c was achieved when 1.5 equiv of the acid 1i and 1 equiv of TfOH were used, whereas the yield of diketone 3w still remained low under these conditions. The hydrolysis of trifluoroacetates 3u, 3v under reflux in dilute HCl was followed by the intramolecular cyclization and led to the

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• synthesis of MMP-inhibitors [63], as discussed later in this review. Aziridines are also obtained as primary products in the addition of chloromethyl phosphonamide 28d to imines. The initial attack leads to a α-chloro-β-amino phosphonamide adduct as intermediate, which then undergoes intramolecular

• cyclization to form the aziridine ring after elimination of chloride. When N-substituted aromatic imines are used, the corresponding aziridines can be reduced at the benzylic carbon to give α-aminophosphonic acids [64]. Synthesis of phosphonamides There are four major methods for the synthesis of

Theoretical studies on the intramolecular cyclization of 2,4,6-t-Bu₃C₆H₂P=C: and effects of conjugation between the P=C and aromatic moieties

• Masaaki Yoshifuji and
• Shigekazu Ito

Beilstein J. Org. Chem. 2014, 10, 1032–1036, doi:10.3762/bjoc.10.103

• alternative Fritsch–Buttenberg–Wiechell-type rearrangement requires almost no activation energy, the intramolecular cyclization needs an activation energy of 12.3 kcal/mol at the MP2(full)/6-31G(d) condition. DFT calculations supported that the optimized structure of the cyclization product of Mes*P=C

• : suggests remarkable conjugation effects between the nearly coplanar P=C skeleton and the aryl moiety. Keywords: 3,4-dihydro-1-phosphanaphthalene; intramolecular cyclization; organophosphorus; phosphanylidenecarbene; steric protection; theoretical calculation; Introduction Sterically demanding groups on

• [10][14]. As an alternative reaction of phosphanylidenecarbenoid, we have previously found the intramolecular cyclization reaction affording 6,8-di-tert-butyl-3,4-dihydro-4,4-dimethyl-1-phosphanaphthalene (2) putatively through formation of phosphanylidenecarbene 1 generated from Mes*P=C(Br)Li (Scheme