Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• involves the 1,5-cyclization of azirinium ylide 9f–h to dihydroazireno[2,1-b]oxazole 10f–h followed by cycloaddition of the latter to ketene 12 to give two regioisomeric adducts 6f,g and 7f–h (Scheme 3). Several examples of the 1,5-cyclization of azomethine ylides bearing an α-keto group into oxazole

• , cyclic analogs of azomethine ylides, are known. This is not surprising in view of the high strain of the azirinium system, and until now ring opening in these systems seemed much more preferable than annelation of a new cycle. Nevertheless, we decided to study two competing pathways for isomerization of

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• rationalized using semi-empirical calculations. In the same contribution, the cascade reactions starting from uracil polyoxin C 106 were described (Scheme 44). Decarboxylative formation of azomethine ylides from 106 and an aldehyde (or ketone), followed by reaction of the ylide with maleimide afforded mixtures

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• organic synthesis [10][11][12][13][14][15][16][17][18][19][20]. For example, dipolar [3 + 2] cycloaddition using azomethine ylides [21] is a powerful class of reactions that permits the synthesis of structural complex molecules in a straightforward way and has been used for the efficient synthesis of this

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• ] cycloadditions, the reaction with azomethine ylides has found great popularity, because it leads to versatile pyrrolidine derivatives of C60. The sources of the ylide can be iminium salts, aziridines, oxazolidines or silylated iminium compounds. In 1993, Prato and coworkers developed the protocol that is now

• used most commonly [31][32]. In the first step, an N-substituted amino acid (e.g., N-methylglycine) reacts with an aldehyde or ketone to generate an azomethine ylides in situ. Trapping of the ylide by a fullerene provides a fullerene-pyrrolidine derivative (8), as illustrated in Scheme 1. In light of

Domino reactions of 2H-azirines with acylketenes from furan-2,3-diones: Competition between the formation of ortho-fused and bridged heterocyclic systems

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Viktoriia V. Pakalnis,
• Roman O. Iakovenko and
• Dmitry S. Yufit

Beilstein J. Org. Chem. 2014, 10, 784–793, doi:10.3762/bjoc.10.74

• considered as dimers of azomethine ylides have been published, though concerted thermal dimerization of azomethine ylides is a forbidden process [33]. According to our calculations the free energy barriers to formation of the azomethine ylides 10a–c from compounds 8a–c are 34.1, 34.7, 32.2 kcal·mol−1 (353 K

Copper–phenanthroline catalysts for regioselective synthesis of pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines and of pyrrolo[1,2-a]phenanthrolines under mild conditions

• Rupankar Paira,
• Tarique Anwar,
• Maitreyee Banerjee,
• Yogesh P. Bharitkar,
• Shyamal Mondal,
• Sandip Kundu,
• Abhijit Hazra,
• Prakas R. Maulik and
• Nirup B. Mondal

Beilstein J. Org. Chem. 2014, 10, 692–700, doi:10.3762/bjoc.10.62

• azomethine ylides, generated in situ from the parent furo[3,2-h]quinoliniums/phenanthroliums, in presence of a copper(II) chloride–phenanthroline catalytic system. The methodology combines general applicability with high yields. Keywords: copper(II) chloride–phenanthroline; 1,3-dipolar cycloaddition; furo

• [3,2-h]quinoliniums; phenanthroliums; pyrrolo[1,2-a]phenanthrolines; pyrrolo[3′,4′:3,4]pyrrolo[1,2-a]furoquinolines/phenanthrolines; Introduction The chemistry of the 1,3-dipolar cycloaddition has always been a fascinating undertaking especially when azomethine ylides are involved as the key component

• recent years, there have been many attempts to synthesize diversely modified pyrrolidines, both symmetric and asymmetric in nature. Several of these attempts involved 1,3-dipolar cycloaddition reactions involving azomethine ylides to give cycloadducts, which were further explored as potential antiviral

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• tautomerization. Instead, an Ag(I) complex based on BINAP and AgSbF6 was employed as a catalyst for the enantioselective 1,3-dipolar cycloaddition reaction of azomethine ylides and alkenes for the synthesis of pyrrolidines 81 and 82 (Scheme 38) [97]. The reaction was developed mainly as a two-component reaction

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

• Chuqin Peng,
• Jiwei Ren,
• Jun-An Xiao,
• Honggang Zhang,
• Hua Yang and
• Yiming Luo

Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33

• employed as starting materials to conduct 1,3-dipolar cycloadditions to yield spirooxindole core structures [16][17][18][19][20]. Owing to the ease of preparation, the azomethine ylides generated from isatin with α-amino acids or amines were frequently chosen as important 1,3-dipolar intermediates to react

• -constructed pyrrolidine. However, unsaturated ketones with α-hydrogens such as benzylideneacetone, which have attracted great interest due to their synthetic potential [40][41][42], have not been exhaustively studied as suitable dipolarophiles for 1,3-dipolar cycloadditions of azomethine ylides to prepare

• spirooxindoles yet [43]. Therefore, extensive studies on the regioselective 1,3-dipolar cycloaddition of azomethine ylides using simple unsaturated ketones, especially ketones having α-hydrogens, are highly desirable, to enrich the library of spirooxindoles and facilitate their biological investigations. Our

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

• Tatyana L. Pavlovskaya,
• Fedor G. Yaremenko,
• Victoria V. Lipson,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Vladimir I. Musatov and
• Alexander S. Karpenko

Beilstein J. Org. Chem. 2014, 10, 117–126, doi:10.3762/bjoc.10.8

• , A.V. Bogatsky physico-chemical institute of the National Academy of Sciences of Ukraine, 86, Lustdorfskaya doroga, 65080, Odessa, Ukraine 10.3762/bjoc.10.8 Abstract The regioselective three-component condensation of azomethine ylides derived from isatins and α-amino acids with acrylamides or

• inhibitors [9][10]. The multicomponent 1,3-dipolar cycloaddition of azomethine ylides, generated in situ via decarboxylative condensation of isatins and α-amino acids with olefinic and acetylenic dipolarophiles, represents a key approach for the regio- and stereoselective construction of a variety of complex

• azomethine ylides, generated in situ via decarboxylative condensation of isatins and N-substituted α-amino acids (sarcosine, proline and thiazolidine-4-carboxilic acid) in a three-component fashion. Results and Discussion The three-component condensation of equimolar amounts of isatins 1, α-amino acids 2 and

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

• María Martín-Rodríguez,
• Luis M. Castelló,
• Carmen Nájera,
• José M. Sansano,
• Olatz Larrañaga,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• unexpected regioselectivity of the 1,3-DC depicted in Scheme 6, calculations within the DFT framework were performed. In the accepted mechanism of the metal catalyzed 1,3-DC of azomethine ylides and acrylates, the α-carbon atom of the azomethine ylide (C2 in Figure 5) reacts with the β-carbon of the acrylate

• was coordinated directly to the gold(I) atom in our model (Figure 5). Analysis of atomic expansion coefficients of the HOMO of Ylide I reveal no significant difference between the azomethine ylides reported in Figure 5. However, Natural Resonance Theory Analysis (NRT) [39][40][41] shows that the

• maleimides. The general scope is not very wide but enantioselections obtained are quite good. Very interesting pyrrolidines with a trans-arrangement were obtained after hydrogenation of the pyrroline precursor. Chiral gold(I) complexes employed in 1,3-DC involving azomethine ylides. Positive non-linear

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• that when tetrahydroisoquinolines (e.g., 41 and 45) were substituted with a methylene group attached to one or two esters, the initially formed iminium ions were readily converted to azomethine ylides. They subsequently underwent 1,3-dipolar cycloaddition with a range of dipolarophiles to form fused

• reaction. Merging Au-based photoredox catalysis and Lewis base catalysis for the Mannich reaction. Merging Ru-based photoredox catalysis and Cu-catalyzed alkynylation reaction. Merging Ru-based photoredox catalysis and NHC catalysis. 1,3-Dipolar cycloaddition of photogenically formed azomethine ylides

The rapid generation of isothiocyanates in flow

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 1613–1619, doi:10.3762/bjoc.9.184

• purification of reaction sequences [40][41][42][43][44]. In addition they have been successfully utilised in order to render dipolar cycloaddition reactions involving azomethine ylides [45][46] as well as nitrile oxides [47][48] more practical for generating important heterocyclic scaffolds such as

Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles

• Steven S. Y. Wong,
• Michael G. Brant,
• Christopher Barr,
• Allen G. Oliver and
• Jeremy E. Wulff

Beilstein J. Org. Chem. 2013, 9, 1419–1425, doi:10.3762/bjoc.9.159

• expedient regio- and stereospecific synthesis of five-membered ring N-, O- or S-containing heterocycles [4][5]. Various 1,3-dipoles can be used, including nitrones [6], azomethine ylides [7], diazoalkanes [8][9] and many others [10][11][12]. α,β-Unsaturated carbonyl compounds are often found to be good

Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

• Yan Sun,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 8–14, doi:10.3762/bjoc.9.2

• derivatives have become an efficient method for the synthesis of various spirooxindoles in recent years [9][10]. It is known that the multicomponent reactions of isatins with in situ formed azomethine ylides have become the efficient synthetic procedure for constructing versatile spirooxindole systems [11][12

Synthesis of fused tricyclic amines unsubstituted at the ring-junction positions by a cascade condensation, cyclization, cycloaddition then decarbonylation strategy

• Iain Coldham,
• Adam J. M. Burrell,
• Hélène D. S. Guerrand,
• Luke Watson,
• Nathaniel G. Martin and
• Niall Oram

Beilstein J. Org. Chem. 2012, 8, 107–111, doi:10.3762/bjoc.8.11

• transformation [2][3][4][5][6][7][8]. We have been studying the intramolecular dipolar cycloaddition of azomethine ylides in synthesis [9][10][11][12][13][14][15][16] and were able to show that the azomethine ylide could be prepared in situ by a cyclization step [17][18]; for example, by heating the aldehyde 1

• the ring junction positions are unsubstituted. Problems with conducting the cascade condensation, cyclisation, cycloaddition chemistry using azomethine ylides derived from enolisable aldehyde substrates [21] has been circumvented by incorporating a one-carbon unit at the alpha-position of the aldehyde

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• 1,3-dipolar cycloaddition of 2-(1-alkynyl)-2-alken-1-ones with α,β-unsaturated imines [49]. Gold-catalyzed (4 + 3) cycloadditions of 1-(1-alkynyl)oxiranyl ketones [50]. (3 + 2) Cycloaddition of gold-containing azomethine ylides [52]. Gold-catalyzed generation and reaction of azomethine ylides [53

Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

• María Martín-Rodríguez,
• Carmen Nájera,
• José M. Sansano,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2011, 7, 988–996, doi:10.3762/bjoc.7.111

• of acrylates as dipolarophiles has only been explored with the 2-thienyliminoesters 6a. Therefore, based on our experience of silver(I)- and gold(I)-catalyzed 1,3-DC involving azomethine ylides derived from α-iminoester 6b and tert-butyl acrylate, we selected a series of known chiral phosphoramidite

• (Sa,R,R)-9 has also been similarly studied. In this case, the matched combination was determined in previous works that investigated the scope of enantioselective silver(I)-catalyzed 1,3-DC of azomethine ylides and dipolarophiles [25][29]. The enantioselectivities were moderate, even when using AgSbF6

• the approach of the mentioned dipolarophile. Conclusion In this work the complexity of the 1,3-DC reaction of azomethine ylides and dipolarophiles (in this case acrylates) was demonstrated. There are many parameters to control and a small variation can cause a dramatic effect in the overall

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33