Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• second half of the molecule has two equivalent ester moieties and a C=N bond instead of a C=C bond leading to an sp3 hybridized C-atom (δ 54.8 ppm) between the equivalent methyl ester groups. The two different N-atoms in B have 15N chemical shifts of −48.1 ppm (C=N) and −211.7 ppm (=N–NH) (Figure 6

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• conformer, a potential energy surface (PES) scan for the rotation around the C–N bond in steps of 10° was done. This scan provided two local minima as well as two maxima (Figure 5). The asymmetric peak shape is caused by the inversion of the pyramidal nitrogen between = 110° and = 120° as well as = 280

• , respectively. The geometries of the E- and Z-ground states of 4 and both transition states (TS1 and TS2) are shown in Figure 6 together with the dihedral angle O–C–N–C1 () and the C–N bond length. Both transition states show a single imaginary frequency (−280.8 cm−1 (TS1) and −364.5 cm−1 (TS2) in hexane and at

• −284.0 cm−1 (TS1) and −362.2 cm−1 (TS2) in the gas phase). This imaginary frequency belongs to the rotational vibration of the formyl hydrogen and the formyl oxygen along the reaction pathway for the E/Z isomerization of 4. In both transition states geometries, the C–N bond (143 pm) is significantly

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

• 28, and the nucleophilic attack on the imine C=N bond could also be synchronized. The two proposed mechanisms are described in Scheme 20 and Scheme 21, respectively. The scope of these reactions has been examined with a wide range of substrates. Therefore, 2-alkynylbenzaldehydes can be functionalized

A catalyst-free multicomponent domino sequence for the diastereoselective synthesis of (E)-3-[2-arylcarbonyl-3-(arylamino)allyl]chromen-4-ones

• Pitchaimani Prasanna,
• Pethaiah Gunasekaran,
• Subbu Perumal and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2014, 10, 459–465, doi:10.3762/bjoc.10.43

• and in a diastereoselective transformation. This transformation generates one C–C and one C–N bond and presumably proceeds via a reaction sequence comprising a Michael-type addition–elimination reaction, a nucleophilic attack of an enamine to a carbonyl reminiscent of one of the steps of the Bayllis

• transformation occurs via a domino sequence of reactions, which generates one C–C and one C–N bond. Presumably, this transformation proceeds via a reaction sequence comprising a Michael-type addition–elimination reaction, a nucleophilic attack of an enamine to a carbonyl, and a final deoxygenation step. We

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• , acetone and hydrazine molecules are distant. When they are close to each other, the geometry of the Me2(O=C)C....NH2–NH2 form was calculated in (ii). It is regarded as a Mulliken charge-transfer (CT) complex, because the C···N distance, 1.614 Å, is larger than the standard C–N bond length of 1.47 Å. The

Studies on the interaction of isocyanides with imines: reaction scope and mechanistic variations

• Ouldouz Ghashghaei,
• Consiglia Annamaria Manna,
• Esther Vicente-García,
• Marc Revés and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2014, 10, 12–17, doi:10.3762/bjoc.10.3

• involves a sequential double isocyanide incorporation into the C=N bond. The final step is a nucleophilic 4-exo-dig cyclization, and the anti addition modes likely lead to less stable stereoisomers which spontaneously isomerize to the observed compounds. Furthermore, we have determined the scope of the

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• as well. The C–N bond is formed concomitantly to the formation of a double bond between the copper ion and the C1 atom of the acetylide. This unusual six-membered copper(III) metallacycle then undergoes a transannular ring contraction to give the copper triazolide. The latter can be protonated to

Reaction of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithiethane with N-vinyl compounds

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2013, 9, 2615–2619, doi:10.3762/bjoc.9.295

• purified 3b was established by single crystal X-ray diffraction (Figure 1). Interestingly, the 19F and 1H NMR spectra of both compounds 3a and 3b show two sets of signals, probably being a result of restricted rotation around the C–N bond in the amide fragment, similar to restricted rotation of –N(CH3)2 in

• a significantly lower rotation barrier around the C–N bond in these two materials. The structures of both 3c and 3d were established by single crystal X-ray diffraction. Compounds 3b and 3e were also prepared in 56–60% yield by using a one-step process in which dimer 1 was generated by the reaction

• 3e showed only one set of signals, despite the fact that in the corresponding cyclopropane (prepared by the reaction of compound 3e with PBu3), restricted rotation around the C–N bond was observed [11]. N-vinylimidazole (4) was found to have a different reactivity profile. The reaction of 4 with 1

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• activated carbonyl compound 9 was also hypothesized (Scheme 4b). 3 Hydroamination of olefins 3.1 Mechanistic considerations Due to the ubiquity of the C–N bond in organic compounds the development of efficient catalytic systems for the hydroamination of olefins is of particular significance from a practical

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Synthesis of axially chiral gold complexes and their applications in asymmetric catalyses

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 2224–2232, doi:10.3762/bjoc.9.261

• structures clearly revealed the presence of a weak gold–π interaction between the Au atom and the aromatic rings in these gold complexes. Because of the gold–π interaction, the C–N bond could not rotate freely, giving two diastereomeric rotamers (S)-15a and (S)-15b. Slaughter and co-workers have also found

• two rotamers in gold complexes 1 caused by the handicap of C–N bond rotation on the basis of X-ray diffraction and named them as “out” rotamer and “in” rotamer [49] (Scheme 5). Their energy barrier has been also disclosed by DFT calculations. Synthesis of the P–Au(I) complexes. The synthesis of the Au

Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification

• Akula Raghunadh,
• Satish S More,
• T. Krishna Chaitanya,
• Yadla Sateesh Kumar,
• Suresh Babu Meruva,
• L. Vaikunta Rao and
• U. K. Syam Kumar

Beilstein J. Org. Chem. 2013, 9, 2129–2136, doi:10.3762/bjoc.9.250

• ][6] or (ii) catalytic oxidations with peroxides and chiral transition metal complexes [7][8][9]. The oxidative esterification of aldehydes involving oxidation followed by a C–O or C–N bond formation has received significant synthetic interest of late. Various transition metal complexes are employed

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• . Oxidative C–C-bond formation gives the hetidine core (233) and C–N-bond formation the hetisine skeleton (234). The first total synthesis of a hetisine-type alkaloid was accomplished by Muratake and Natsume in 2004 [177]. In their seminal work, (±)-nominine (225) was synthesized within 40 steps and 0.15

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

• 15 by abstraction of a hydrogen atom directly. The addition of the enol form of α-ketoester 59 to 15 furnishes the Mannich adduct 60. A retro-aza-Michael reaction via enol 61 allows cleavage of the C–N bond to yield secondary aniline 62. Aniline 62 is first oxidized to imine 63, which is further

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• ) [126]. The suggested mechanism begins with a C–N bond rotation by chelating ligand dissociation forming species 46, which is stabilized by solvent coordination. Eventually, an agostic interaction in 47 prior to the rate-determining C–H bond cleavage should displace the solvent molecule. An oxidative

Palladium-catalyzed synthesis of N-arylated carbazoles using anilines and cyclic diaryliodonium salts

• Stefan Riedmüller and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2013, 9, 1202–1209, doi:10.3762/bjoc.9.136

• present an alternative Pd-catalyzed method for the construction of N-substituted carbazoles based on a stable, cyclic iodonium salt and electron-deficient anilines [24][25]. In the initial C–N bond-forming step of this cascade reaction, a ring opening of the cyclic iodonium salt through the amine is

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

• Josué M. Silla,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• electron donors than halogens in these cases. This interaction is explicitly expressed for 8b and 9c by means of X∙∙∙B bond paths in QTAIM (Figure 7). Indeed, the B–C–C(N) bond angle in 8c and 9c is significantly curved to allow the formation of a four-membered ring, reflecting the effectiveness of the X/B

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

• reaction of chiral imines with enolates derived from Weinreb amides [13][14]. In previous work on the asymmetric synthesis of 2,6-disubstituted piperidines by C–N bond formation, we demonstrated that intramolecular aza-Michael ”type” cyclisation [15] using a β'-carbamate-α,β-unsaturated ketone

Palladium-catalyzed C–N and C–O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols

• Rajendra Surasani,
• Dipak Kalita,
• A. V. Dhanunjaya Rao and
• K. B. Chandrasekhar

Beilstein J. Org. Chem. 2012, 8, 2004–2018, doi:10.3762/bjoc.8.227

• report on coupling of amides, amino acid esters and phenols with N-protected 4-bromo-7-azaindole derivatives. Keywords: 7-azaindole; C–N bond; C–O bond; ligand; palladium catalyst; Introduction Palladium-catalyzed C–N and C–O bond-forming reactions between 4-substituted 7-azaindoles and amides, amines

• prepare [6]. Initially, coupling of 4-bromo-1-ethyl-1H-pyrrolo[2,3-b]pyridine (1d) with phenylmethanamine (4a) was selected as a model reaction to optimize the reaction condition of C–N-bond formation of amines. The experimental results are summarized in Table 3. After the screening of various ligands

• amines. As seen from Table 4, the cross-coupling reaction of N-protected 4-bromo-7-azaindoles 1a–1d with various amines 4a–4f proved to be general under the optimized conditions to get the coupled products 5a–5f in very good yield (88–94%) within a reasonable time of 2.5 to 3 h. The C–N-bond-forming

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

• -derived enolates [65][66][67][68][69][70], in particular, under similar conditions. Thus, the ionized form of α-hydroxy intermediate 17 can undergo the cleavage of the glycine C–N bond [65][68][69][70] resulting in the formation of neutral complex 18. Previously, we demonstrated that in situ formed

N-Heterocyclic carbene–palladium(II)-1-methylimidazole complex catalyzed Mizoroki–Heck reaction of aryl chlorides with styrenes

• Ting-Ting Gao,
• Ai-Ping Jin and
• Li-Xiong Shao

Beilstein J. Org. Chem. 2012, 8, 1916–1919, doi:10.3762/bjoc.8.222

• -diisopropylphenyl)imidazolium chloride], and 1-methylimidazole in a one-step procedure in high yield, was an effective catalyst in C–C and C–N bond-formation reactions [37][38][39][40][41][42][43][44]. In our continuing investigations on the further applications of this complex in organic synthesis, we found that

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• regenerates the Pd(0) species. The intramolecular Pd(II)-catalyzed reaction of the 1-allyl-2-indolecarboxamides 41 leads to the pyrazino[1,2-a]indoles 43 through the conversion of the olefinic C–H bond into a C–N bond (Scheme 21) [79]. The cyclization process resulted in the initially formed exomethylenic

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives

• Esteban P. Urriolabeitia,
• Eduardo Laga and
• Carlos Cativiela

Beilstein J. Org. Chem. 2012, 8, 1569–1575, doi:10.3762/bjoc.8.179

• different reactivity. Therefore, the attack of the oxygen of an O-bonded alcohol on the electrophilic acyl carbon in our complexes seems to be favoured, since no demethylation is involved, and the C–O coupling occurs selectively instead of the intramolecular C–N bond formation. It seems that the reaction is

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• migration of the N-acyl glycine derivatives [18]. The other consists of C–N bond-forming reactions, such as (c) a rhodium-catalyzed N–H insertion reaction with α-diazo-β-keto esters [19][20][21], and (d) α-oxidation of β-keto esters to the corresponding oximes and the subsequent hydrogenation [22]. However

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• cation adduct than in the neutral amine. Figure 2 shows the projection through the C–N bond of one of the isopropyl-groups in 16Me. Trialkyl- and triarylphosphanes are equally potent nucleophiles, whose use in catalytic processes is, however, often limited due to their oxygen sensitivity. Table 2 lists

• calculated for these systems thus represent the reaction enthalpies for the formation of ion-dipole complexes. Aside from DABCO this is the case for 345, 45, and 347. The C–N bond distances of the energetically best conformations of these complexes range from 2.8 Å to 4.0 Å. As a reference bond length the C

• –N distance in pyridine-trityl adduct (1TT), which amounts to 1.57 Å, can be used. A slightly increased C–N bond length can be found for the TCA-adduct of quinuclidine 53 (1.76 Å), which is in distinct contrast to the structurally similar DABCO. It should be added that all other electrophiles