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

• on the carbonyl group of the aldehyde affords 7. Then 7 provides the target product via two different reaction pathways. The first route is that 7 loses a water molecule to afford the Schiff base 8. Then 8 undergoes a Pinner reaction and imine 9 is formed, and then 9 turns into 10 through

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• generation catalyst but exhibited very high termal stability (Figure 16). In 2002 and 2003, the Verpoort group synthesized and applied a variety of Schiff base adapted complexes in RCM [87] and ROMP [87][93][94][96][97] reactions (Scheme 10). This class of complexes showed high activity and very high

• 2009, surely inspired by the aforementioned work, the Verpoort group reported a family of indenylidene Schiff base–ruthenium complexes (111a–f, Figure 17) for CM and RCM reactions in air [98]. They combined the higher thermal stability of indenylidene complexes and the tunability and stability of

• Schiff base ligands. These complexes were able to perform CM and RCM reactions in air with lower catayst loadings compared to 105a–f, 106a–f, 107a–f and 111a–c. RCM reactions proceeded smoothly using N,N-diallyltosylamide (46) giving, with all catalysts, quantitative yields. When a more challenging

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• of cocatalyst. While first examples of latent catalysts were based on phosphine-containing ruthenium complexes bearing a Schiff base ligand (O–N) [9] replacement of the phosphine ligand by sterically demanding and strongly σ-donor N-heterocyclic carbenes (NHC) afforded catalysts with improved

• an interesting alternative to indenylidene-Schiff base complexes that in most cases require toxic thallium salts for their preparation [23][24]. Here, we report the synthesis of (NHC)Ru–indenylidene complexes incorporating chelating picolinic ligands and evaluate their potential as latent catalysts

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• structures virtually unlimited. Complexes incorporating alkylidene ligands based on aromatic [12][13][14][15] or aliphatic amines [16][17] and Schiff base patterns [18][19][20][21][22] have been prepared so far, exhibiting diverse activities ranging from very fast to very slow initiation. Furthermore, in

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• explored [15][16][17], mainly due to the high-lying HOMO energy levels leading to a thermodynamically unfavorable dye regeneration. To overcome this problem, we recently applied a Schiff-base reaction to obtain a rigid and planar quinoxaline-fused TTF-based dye that shows an intense optical ICT absorption

Tuning of tetrathiafulvalene properties: versatile synthesis of N-arylated monopyrrolotetrathiafulvalenes via Ullmann-type coupling reactions

• Vladimir A. Azov,
• Diana Janott,
• Dirk Schlüter and
• Matthias Zeller

Beilstein J. Org. Chem. 2015, 11, 860–868, doi:10.3762/bjoc.11.96

• comparing two possible copper(I) ligands (Figure 2): trans-diaminocyclohexane (DACH) 9a, which was employed before in N-arylations with pyrrolo-TTFs [17][18][19], and its Schiff base derivative 9b, which was reported to be one of the most effective ligands in similar N-arylation reactions with other

Fluoride-driven ‘turn on’ ESPT in the binding with a novel benzimidazole-based sensor

• Kai Liu,
• Xiaojun Zhao,
• Qingxiang Liu,
• Jianzhong Huo,
• Bolin Zhu and
• Shihua Diao

Beilstein J. Org. Chem. 2015, 11, 563–567, doi:10.3762/bjoc.11.61

• -mentioned proton in BIP. To further explore the photophysical sensing properties of BIP with various anions (F−, Cl−, Br−, I−, H2PO4−, NO3−, AcO−, added as TBA salts), fluorescence measurements were carried out. The weak fluorescence emission at 411 nm, corresponding to the enol form of a Schiff base [32

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

• 48 h the reaction proceeded to form mainly two compounds – Knoevenagel adduct 7 and Schiff base 8 (Scheme 3). Trace amounts of 2-hydroxy-N-(2-methoxyphenyl)-2-methyl-4-(3-methylisoxazol-5-ylamino)chroman-3-carboxamide (4a) were detected in the reaction mixture as well. Furthermore, both conventional

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

• addition of trimethylsilylcyanide to the formed Schiff-base provided aminonitrile 168 as the major diastereomer (dr 95:5). Oxidative cleavage of the phenylglycinol moiety with Pb(OAc)4 liberated the amino-functionality and hydrolysis of the amide and nitrile under acidic conditions finally gave DCG-IV (162

• diastereomer (Scheme 21). Conversion of tert-butyl ester 170 into aldehyde 171 by a two-step protocol was followed by condensation with (R)-α-phenylglycinol and treatment of the formed Schiff base with trimethylsilylcyanide to afford α-aminonitrile 172 as major isomer (dr > 4:1). Oxidative cleavage with Pb(OAc

Carbohydrate PEGylation, an approach to improve pharmacological potency

• M. Eugenia Giorgi,
• Rosalía Agusti and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 1433–1444, doi:10.3762/bjoc.10.147

• imine (Schiff base), which was subsequently reduced to PEG-g-chitosan with sodium cyanoborohydride [55], allowing retention of net charge. PEGylation can also be accomplished by condensation of the free amino groups with activated PEGs, such as PEG-NHS or PEG-p-nitrophenyl carbonate, converting the

Microwave-assisted Cu(I)-catalyzed, three-component synthesis of 2-(4-((1-phenyl-1H-1,2,3-triazol-4-yl)methoxy)phenyl)-1H-benzo[d]imidazoles

• Yogesh Kumar,
• Vijay Bahadur,
• Anil K. Singh,
• Virinder S. Parmar,
• Erik V. Van der Eycken and
• Brajendra K. Singh

Beilstein J. Org. Chem. 2014, 10, 1413–1420, doi:10.3762/bjoc.10.145

• corresponding Schiff’ base, which further cyclizes to dihyrobenzimidazole. Finally, D-glucose [37] oxidizes the dihyrobenzimidazole to the benzimidazole. Moreover, if the reaction proceeds via route B the benzimidazole formation from 4-(prop-2-yn-1-yloxy)benzaldehyde 2a and 1,2-diaminobenzene 3a takes place

A novel family of (1-aminoalkyl)(trifluoromethyl)- and -(difluoromethyl)phosphinic acids – analogues of α-amino acids

• Natalia V. Pavlenko,
• Tatiana I. Oos,
• Yurii L. Yagupolskii,
• Igor I. Gerus,
• Uwe Doeller and
• Lothar Willms

Beilstein J. Org. Chem. 2014, 10, 722–731, doi:10.3762/bjoc.10.66

• bearing a carboxylate functionality to obtain aminocarboxylic acids, containing pendant CF3 or CHF2 phosphinic acid linkages. Thus, phosphinic acids 1 and 6 reacted with the N-Boc-protected Schiff base of ethyl glyoxalate 22 [32] under mild conditions to produce the N-deprotected phosphinylglycines 23 and

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

• Suresh Babu Meruva,
• Akula Raghunadh,
• Raghavendra Rao Kamaraju,
• U. K. Syam Kumar and
• P. K. Dubey

Beilstein J. Org. Chem. 2014, 10, 471–480, doi:10.3762/bjoc.10.45

• -ethanone under aerial oxidation conditions [24]. Later this methodology was successfully employed in the synthesis of isoquinoline alkaloids [27]. The synthesis of eudistomin Y (6) was initiated with the conversion of the respective 2,2-dibromo-1-phenylethanone to the corresponding Schiff base 14 by

• reaction with tryptamine in presence of NaI. The Schiff base on in situ oxidation with cumene hydroperoxide afforded an unstable oxaziridine derivative 15. Ring opening of the oxaziridine derivative 15 in presence of base afforded ketoiminol 16, which on iminol–amide tautomerism provided the required α

Synthesis and stereochemical assignments of diastereomeric Ni(II) complexes of glycine Schiff base with (R)-2-(N-{2-[N-alkyl-N-(1-phenylethyl)amino]acetyl}amino)benzophenone; a case of configurationally stable stereogenic nitrogen

• Hiroki Moriwaki,
• Daniel Resch,
• Hengguang Li,
• Iwao Ojima,
• Ryosuke Takeda,
• José Luis Aceña and
• Vadim A. Soloshonok

Beilstein J. Org. Chem. 2014, 10, 442–448, doi:10.3762/bjoc.10.41

• preparation of α-AAs is focused on simplicity of the experimental procedures and cost of the target α-AAs. Among various chiral nucleophilic glycine equivalents, the Ni(II) complex of glycine Schiff base 1 (Figure 1) possesses some attractive characteristics that underscore its potential commercial

• novel and advanced structural type of Ni(II) complexes using an inexpensive and nonracemizable chiral auxiliary. As the first step in this direction, here we describe the preparation of Ni(II) complexes of glycine Schiff base with α-phenylethylamine-derived ligands. One unusual feature of these new

• ) stereochemistry to the complexes 6b–e. Conclusion In conclusion, this exploratory work has revealed that: 1) Application of α-phenylethylamine as the source of stereochemistry information in the novel Ni(II) complexes, results in the formation of diastereomeric glycine Schiff base products due to the

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• illustrates a strategy for achieving stereoselectivity in C–F bond formation. The racemic β-lactam 4b was synthesised as a single diastereoisomer from the Schiff base 79 (Scheme 11), by a Reformatsky addition followed by spontaneous cyclisation; removal of the amine protecting group under oxidative conditions

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

• Alexander Penger,
• Cortney N. von Hahmann,
• Alexander S. Filatov and
• John T. Welch

Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303

• mentioned above, the preparation of N-ethyl 3,3,3-trifluoropropanaldimine, the Schiff base of 3,3,3-trifluoropropanal, was accompanied by enamine formation, likely as a consequence of the acidity of the proton α to the trifluoromethyl group [45][47]. Not surprisingly, 5 was relatively reactive. After

• SF5Cl to enol ethers and the subsequent acidic hydrolysis of 3. Formation of Schiff base 5 is problematic but, in contrast to the reactions of the analogous trifluoromethyl compounds, does successfully proceed. Even with a manifold of possible side reactions, β-lactam formation by the ketene–imine

Complete σ* intramolecular aromatic hydroxylation mechanism through O₂ activation by a Schiff base macrocyclic dicopper(I) complex

• Albert Poater and
• Miquel Solà

Beilstein J. Org. Chem. 2013, 9, 585–593, doi:10.3762/bjoc.9.63

• and C–O bond formation, followed finally by a proton transfer to an alpha aromatic carbon that immediately yields the product [CuII2(bsH2m-O)(μ-OH)]2+. Keywords: aromatic hydroxylation; C–H bond activation; C–H functionalization; copper; DFT calculations; mechanism; Schiff base; Introduction Bearing

• . Indeed, for the CuI2(bsH2m)]2+ system this step displays the upper barrier of the overall reaction pathway a→g. Conclusion To sum up, the intramolecular hydroxylation of a Schiff base hexaazamacrocyclic dicopper(I) complex (a) by means of O2 to finally yield the μ-phenoxo-μ-hydroxo product (g) occurs

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• by milling protected glycine hydrochloride 21 and diphenylmethanimine (20), under solvent-free conditions (Scheme 11) [62]. The asymmetric alkylation of glycine imine 22 was carried out by using a phase-transfer catalyst under basic conditions in a ball-mill. The Schiff base reacted rapidly with

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• complex 15 was obtained. As it follows from these results, only one carbonyl group in the starting ligands 12 was involved in the formation of the corresponding Schiff base with glycine, similar to the reactivity observed for tridentate ligands with Ni(II) [49][50][51][52][53]. In the 1H and 13C NMR

• elements of chirality giving rise to the most stable diastereomeric stereochemistry. The distances of the Ni–O(5) [1.8651(13) Å] and Ni–N(4) [1.8569(16) Å] bonds of the five-membered chelate ring of the glycine Schiff base fragment were relatively similar, while the bonds Ni–N(3) [1.8417(16) Å] and Ni–N(2

Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions

• Kyle F. Biegasiewicz,
• Michelle L. Ingalsbe,
• Jeffrey D. St. Denis,
• James L. Gleason,
• Junming Ho,
• Michelle L. Coote,
• G. Paul Savage and
• Ronny Priefer

Beilstein J. Org. Chem. 2012, 8, 1814–1818, doi:10.3762/bjoc.8.207

• , MA 01119, USA 10.3762/bjoc.8.207 Abstract Recently, a novel chiral cubane-based Schiff base ligand was reported to yield modest enantioselectivity in the Henry reaction. To further explore the utility of this ligand in other asymmetric organic transformations, we evaluated its stereoselectivity in

• /fragmentation to afford benzaldehyde, which further reacts to give benzyl benzoate [18]. Recently, we synthesized the first cubane-based Schiff base ligand (Figure 1) and screened it in the Henry reaction in the synthesis of β-nitroalcohols [19]. The cubyl moiety can be considered a cross between a tert-butyl

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• fluorophores via a Schiff base structure. In a previous work, we developed a new class of diarylethenes with a naphthalene group and a thiophene group. The results revealed that these molecules have excellent photochromism with good fatigue resistance and thermal stability [37]. In this study, in order to

The cross-metathesis of methyl oleate with cis-2-butene-1,4-diyl diacetate and the influence of protecting groups

• Arno Behr and
• Jessica Pérez Gomes

Beilstein J. Org. Chem. 2011, 7, 1–8, doi:10.3762/bjoc.7.1

• base ligands, they must be chemically activated by the addition of 100 equiv of phenyltrichlorosilane [30][31]. Within this catalyst family it can be concluded that with higher steric hindrance of the Schiff base ligands higher conversions and yields were achievable (Table 1, entries 7 and 8). Schiff

• base ligands with a nitro substituent did not lead to a significant increase or loss of metathesis activity. Consequently, in the oleochemical cross-metathesis reaction [Ru]-7 and [Ru]-8 were the most active catalysts due to their space-filling isopropyl substituted Schiff base ligands [31]. The cross

• -metathesis of methyl oleate (1) with cis-2-butene-1,4-diyl diacetate (2) was feasible with the relatively low catalyst loading of the Schiff base ruthenium catalyst [Ru]-7 to yield two value-added and sustainable intermediates in one step. Methyl 11-acetoxyundec-9-enoate (3) and undec-2-enyl acetate (4) are

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• hindrance by the aromatic units towards the formyl group, compound 21 [4] was reacted with ethylenediamine in the presence of a catalytic amount of acetic acid (Scheme 5). The Schiff base product 22 was obtained in 62% yield as a pale brown crystalline solid. Although highly strained and buckled TTF

Structural studies on encapsulation of tetrahedral and octahedral anions by a protonated octaaminocryptand cage

• I. Ravikumar,
• P. S. Lakshminarayanan,
• E. Suresh and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2009, 5, No. 41, doi:10.3762/bjoc.5.41

• to the aldehyde also dissolved in dry methanol. Reduction of the resulting Schiff base was achieved using NaBH4. Both higher temperatures (40–50 °C) and fast addition rates lead to mostly polymeric products in the scaled-up synthesis. In the case of 1, a white precipitate is obtained after addition