Visible light mediated intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes

• Theresa H. Nguyen,
• Soumitra Maity and
• Nan Zheng

Beilstein J. Org. Chem. 2014, 10, 975–980, doi:10.3762/bjoc.10.96

• ; visible light; Introduction Cyclopropanes have been used as a three-carbon synthon to prepare a diverse array of organic compounds [1][2][3][4]. The unusual reactivity, exhibited by cyclopropanes, is largely due to their inherent ring strain that makes cleavage of the C–C bonds facile [5]. A number of

The difluoromethylene (CF₂) group in aliphatic chains: Synthesis and conformational preference of palmitic acids and nonadecane containing CF₂ groups

• Yi Wang,
• Ricardo Callejo,
• Alexandra M. Z. Slawin and
• David O’Hagan

Beilstein J. Org. Chem. 2014, 10, 18–25, doi:10.3762/bjoc.10.4

• 23. The lithium methylenedifluoroacetylide (RCF2C≡CLi) reaction to form a C–C bond, provides a particularly useful synthon to access this 1,4-di-CF2 motif. Oxidation and then treatment of the resultant ketone 24, with DAST generated the tetrafluoroacetylene 25. Complete hydrogenation of the triple

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

• minimization of unfavourable hydrophobic interactions. Results and Discussion The use of fluoroalkylimines to form β-lactams has proven especially useful in synthesis [24][25][26] especially in the Ojima β-lactam synthon method [27][28][29] used to prepare docetaxel analogs [26]. The general utility of the

Oxidative 3,3,3-trifluoropropylation of arylaldehydes

• Akari Ikeda,
• Masaaki Omote,
• Shiho Nomura,
• Miyuu Tanaka,
• Atsushi Tarui,
• Kazuyuki Sato and
• Akira Ando

Beilstein J. Org. Chem. 2013, 9, 2417–2421, doi:10.3762/bjoc.9.279

• used in place of (3,3,3-trifluoropropynyl)lithium, which can add to carbonyl compounds and couple with aryl halides through a zinc intermediate. For the 3,3,3-trifluoropropenyl synthon Yamazaki et al. reported the use of 2-(trifluoromethyl)-1-(phenylsulfenyl)vinyltrimethylsilane for the addition to

Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

• Adrián Gómez-Suárez,
• David J. Nelson,
• David G. Thompson,
• David B. Cordes,
• Duncan Graham,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

• )] (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), using [AuCl(IPr)] and an excess of KOH in THF [14][15]. This complex has proven to be an excellent synthon for the preparation of a wide variety of organogold(I) species [16][17][18][19][20][21][22][23]. Two approaches have been developed

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• gelation are known. The presence of a supramolecular synthon to promote the one-dimensional (1D) self-assembly is a necessary feature in order to form the fibrillar entangled network that entraps the solvent [14]. The strongest and most important supramolecular synthons involve functional groups that

• promote the one-dimensional growth. These concepts have been recently exploited to design new LMOGs [15][16]. Nevertheless, the presence of a supramolecular synthon in a molecule is a necessary but not a sufficient feature to become an organogelator. The formation of the gel involves a delicate balance of

• of 1 demonstrating that templated silica nanotubes are obtained only under controlled conditions. Considering that the design of new LMOGs with predictable gelation properties is still a challenge nowadays, we consider that the trans-diaxial dihydroxy supramolecular synthon studied herein is a

Efficient synthesis of β’-amino-α,β-unsaturated ketones

• Isabelle Abrunhosa-Thomas,
• Aurélie Plas,
• Nishanth Kandepedu,
• Pierre Chalard and
• Yves Troin

Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52

• incorporating β-amino ketone functionality are prevalent in many natural products of biological importance [1]. This versatile synthon has been extensively used in the construction of β-amino acids [2], β-amino alcohols [3], and homoallylic amines [4][5], and can serve as building blocks for the preparation of

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• coumarinylacetic acid, which was then reduced to an alcohol by borane-dimethyl sulfide. After the phenolic hydroxy group was protected with a tert-butyl(dimethyl)silyl group, the alcohol was converted into a bromide and was used to alkylate a glycine enolate synthon to afford an imine. All the protecting groups

Enantioselective total synthesis of (R)-(−)-complanine

• Krystal A. D. Kamanos and
• Jonathan M. Withey

Beilstein J. Org. Chem. 2012, 8, 1695–1699, doi:10.3762/bjoc.8.192

• functionalities. Synthetic studies, also conducted by Nakamura and Uemura, established the absolute structure and configuration as (R)-(−)-complanine (Figure 1), showing it to be related to other natural products that possess the vicinal amino alcohol moiety. Using a chiral-synthon approach, (R)-(−)-complanine

The Amadori rearrangement as glycoconjugation method: Synthesis of non-natural C-glycosyl type glycoconjugates

• Katharina Gallas,
• Gerit Pototschnig,
• Florian Adanitsch,
• Arnold E. Stütz and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2012, 8, 1619–1629, doi:10.3762/bjoc.8.185

• cyanohydrin reaction procedure. Results and Discussion C-Elongation In an initial C-elongation attempt, with the aim to avoid HCN as C-synthon, we decided to follow a protocol employing sodium cyanide, as described by Hudson [29] (Scheme 2). By this reaction sequence, starting from aldohexose 1, the obtained

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• work of Lu [11][12][13][14][15][16][17][18][19][20], all phosphine-mediated [3 + 2] annulations proceeded through an important intermediate “1,3-dipolar synthon”. The formation of a 1,3-dipolar synthon by using a catalytic amount of phosphines have been directed toward the following two paths

• : phosphines attack the middle carbon atom of allenes to produce the 1,3-dipolar synthon (Scheme 1, reaction 1), and phosphines add to the β-position of MBH carbonate to remove carbon dioxide and tert-butanol, affording the 1,3-dipolar synthon (Scheme 1, reaction 2). Concerning the asymmetric [3 + 2

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• existing indole framework. In general, applications of this construction sequence fall into two major camps, namely condensations routed through a 2-aminoindole synthon [49][50][51][52][53][54][55][56], and those targeting pyridine closures onto a 2-oxindole [57][58]. In addition, intramolecular Hartwig

Branching out at C-2 of septanosides. Synthesis of 2-deoxy-2-C-alkyl/aryl septanosides from a bromo-oxepine

• Supriya Dey and
• Narayanaswamy Jayaraman

Beilstein J. Org. Chem. 2012, 8, 522–527, doi:10.3762/bjoc.8.59

• envisaged that III would form as a synthon to implement C–C bond forming reactions. Vinyl halide 2 was synthesized through a ring-expansion reaction of cyclopropanated adduct 1 (Scheme 1), as reported previously [21]. The reactivity at C-2 of 2 was examined by the chosen organometallic reactions, namely

Lithium phosphonate umpolung catalysts: Do fluoro substituents increase the catalytic activity?

• Anca Gliga,
• Bernd Goldfuss and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2011, 7, 1189–1197, doi:10.3762/bjoc.7.138

• metallophosphonate catalyst must act as a nucleophile, an anion (d1-synthon) stabilization group, and as well as a leaving group (nucleofuge). Comparative computational assessments of carbanionic d1-species, which have been proposed as crucial intermediates according to the Lapworth and Breslow mechanisms, show

• observed for a benzylic fencholate, when the benzylic positions were occupied by CF3-groups (92% versus 19% yield, Scheme 2) [26]. This increased reactivity is thought to arise from a favored formation of the carbanionic d1-synthon intermediate, due to the electron withdrawing effect of the CF3 groups. A

• high as the yield achieved with phosphonate 15. The reduction of the nucleophilic character of the phosphorus nucleophile in the first step of the catalytic cycle, and of the d1-synthon in the third step of the catalytic cycle (Scheme 1), could explain these results. The increased 1J(P–H) coupling

A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• -amino-4-methylcoumarin; p-nitroaniline; proteolytic substrate; selenocarboxylate/azide amidation; synthon; Introduction Chromogenic and fluorogenic amino acid/peptide conjugates are widely used as substrates in enzyme assays for protease activity and specificity [1]. Proteolytic cleavage of the amino

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• complexes bearing N-heterocyclic carbenes (NHC) [9][10] as supporting ligands has enabled the isolation of a “golden synthon”, [Au(OH)(IPr)] 1 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), that is able to participate in metalation reactions with aromatic C–H bonds (Scheme 1) [11]. The reactivity

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• -propanol, butanol) or in DMF (Scheme 49) [92]. Conclusion 5-Aminopyrazole is an important heterocyclic system which has great significance in pharmaceutical industry as well as being a useful synthon for the synthesis of many bridgehead heterocycles. This review describes new strategies and the development

Chiral gels derived from secondary ammonium salts of (1R,3S)-(+)-camphoric acid

• Tapas Kumar Adalder,
• N. N. Adarsh,
• Ravish Sankolli and
• Parthasarathi Dastidar

Beilstein J. Org. Chem. 2010, 6, 848–858, doi:10.3762/bjoc.6.100

• )-(+)-camphoric acid and various secondary amines were prepared based on supramolecular synthon rationale. Out of seven salts prepared, two showed moderate gelation abilities. The gels were characterized by differential scanning calorimetry, table top rheology, scanning electron microscopy, single crystal and

• ; supramolecular gels; supramolecular synthon; Introduction A gel is a two component system which is mainly liquid with a very little amount of solid. In gel state, gelator molecules form 3-D networks within which solvent molecules are trapped thus resulting in a gel. Depending on the nature of the network, gels

• a known gelator scaffold. But recent advances in the supramolecular chemistry [33] and crystal engineering [34] has made it possible to design a gelator molecule in a rational manner by exploiting a supramolecular synthon [35] approach, at least for certain classes of gelling agents [3]. We have

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• , alkylation of a glycine enolate with the primary bromide 5 was anticipated. Indeed, its use as the electrophilic component in the coupling with the benzophenone-derived imine of tert-butyl glycine 6, which functioned, after deprotonation, as a synthetic equivalent of a glycine enolate synthon, led to the

Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones

• Dhilli Rao Gorja,
• Venkateswara Rao Batchu,
• Ashok Ettam and
• Manojit Pal

Beilstein J. Org. Chem. 2009, 5, No. 64, doi:10.3762/bjoc.5.64

• bioactive molecules, the pyrazole framework plays an important role in pharmaceutical research. We therefore believe that the present methodology and the product pyranopyrazol-4-one being a potential synthon for more complex heterocycles may find wide applications in organic synthesis, especially in

Coaxial electrospinning of liquid crystal-containing poly(vinylpyrrolidone) microfibres

• Eva Enz,
• Ute Baumeister and
• Jan Lagerwall

Beilstein J. Org. Chem. 2009, 5, No. 58, doi:10.3762/bjoc.5.58

• 8CB (Synthon Chemicals GmbH) was pumped at room temperature through an inner capillary of 320 μm inner and 450 μm outer diameter (fused silica tubing, BGB Analytik AG). The spinneret–collector distance was kept constant at 10 cm. With a high voltage power supply (Gamma High Voltage Research) a voltage

Preparation and Diels–Alder/cross coupling reactions of a 2-diethanolaminoboron- substituted 1,3-diene

• Liqiong Wang,
• Cynthia S. Day,
• Marcus W. Wright and
• Mark E. Welker

Beilstein J. Org. Chem. 2009, 5, No. 45, doi:10.3762/bjoc.5.45

• serve as a synthon for a host of other organic dienes, we took cycloadducts 3–5 and proved that they could be cross coupled efficiently to iodobenzene, 4-trifluoromethyl-1-iodobenzene, and 4-iodoanisole (Table 2, Scheme 3). Cross coupled cycloadducts 6–14 were all isolated in good to excellent yield and

• –Alder reactions that we have prepared to date. We have also demonstrated that this boron-substituted diene can serve as a synthon for a host of organic dienes via cross coupling reactions which we performed on Diels–Alder reaction cycloadducts. Experimental Preparation of 1,3-butadiene-2-diethanolamine

(−)-Complanine, an inflammatory substance of marine fireworm: a synthetic study

• Kazuhiko Nakamura,
• Yu Tachikawa and
• Daisuke Uemura

Beilstein J. Org. Chem. 2009, 5, No. 12, doi:10.3762/bjoc.5.12

• inflammatory substance of Eurythoe complanata, was accomplished by a “chiral synthon” approach. The absolute configuration of this molecule was determined to be R. Keywords: chiral synthon; complanine; inflammatory substance; marine fireworm; total synthesis; Introduction Toxic marine annelids were first

• absolute structure of complanine was unambiguously determined by means of synthetic methodology by a “chiral synthon” approach. Related amino alcohols possessing olefins from marine natural resources have been identified [3][4], but synthetic studies of these compounds have not been reported. Results and

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• (Scheme 9). As shown in Scheme 9, the strategy employed allows the selective formation or 1- or 3-substituted derivatives, where the coupling of a C2 acetylenic synthon and a C2 epoxide synthon provides a new and useful [2+2] annulation strategy for the preparation of the strained cyclobutene ring. The