Approaches to α-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

• Sosale Chandrasekhar and
• V. Mohana Rao

Beilstein J. Org. Chem. 2012, 8, 1393–1399, doi:10.3762/bjoc.8.161

• . The geometry around the partial double bond of the amide C–N linkage in 5a is also Z (Figure 1). This is probably a consequence of steric repulsion between the N-substituent and the phenyl residue in the alternative E isomer. NMR spectra likewise did not indicate isomerism around the amide C–N bond in

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

• 3-arylpyridines also found application [43][44], and likewise falls into the category of indole ring closure onto an existing substituted pyridine, though in this case with the formation of the C–N bond. More recently, the group of Cuny has reported two strategies that exploit cross-couplings to

• –Buchwald cross-coupling onto a 2-bromoindole, with formation of the pyridine was reported by Dodd [59], and C–N bond closures in presumed nitrogen-radical processes have also been reported by Narasaka [60][61]. Electrocyclic ring closures forming the pyridine ring from 2-aminoindole-derived intermediates

Synthesis of axially chiral oxazoline–carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe₂

• Feijun Wang,
• Shengke Li,
• Mingliang Qu,
• Mei-Xin Zhao,
• Lian-Jun Liu and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 726–731, doi:10.3762/bjoc.8.81

• , affording the corresponding Au(I) complexes in moderate to high yields. Keywords: axially chiral ligand; gold; N-heterocyclic carbenes; N-naphthyl framework; Introduction During the past decade, with an explosive growth of asymmetric homogeneous gold catalysis in C–C, C–O, or C–N bond formations, the

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• low yield. The formation of 20 could be explained by a subsequent SmI2-mediated reduction of the C=N bond formed by ring opening of 19, which contains a hemiaminal moiety. This suggestion is supported by the 1H NMR spectrum of 19 in which a second set of signals could be easily detected. Thus, the

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• precursor 49 in situ through a Pd/Cu mediated coupling reaction between (trimethylsilyl)acetylene (TMSA) with an aryl iodide, followed by a desilylation reaction. The subsequent addition of the third partner, an o-iodoanilide derivative, allowed a Pd/Cu tandem C–C/C–N-bond-forming reaction. The main

Reductive amination with zinc powder in aqueous media

• Giovanni B. Giovenzana,
• Daniela Imperio,
• Andrea Penoni and
• Giovanni Palmisano

Beilstein J. Org. Chem. 2011, 7, 1095–1099, doi:10.3762/bjoc.7.125

• dehydrative condensation to give an imine or an iminium ion, the latter being formally hydrogenated to the final amine product. The selectivity of the reducing agent is crucial as it should efficiently reduce the C=N bond of the intermediate while leaving unaffected the potentially reducible carbonyl compound

• . In addition, the desired reduction of the C=N bond may be accelerated by working in the presence of weak acids, thus allowing protonation of the C=N nitrogen atom but not of the carbonyl oxygen; the reducing agent, usually a hydride, should then be reasonably stable in the presence of acidic

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• enriched secondary propargyl alcohols led to the chiral oxetan-3-one with no apparent racemization (Scheme 20). 3 Gold-catalyzed C–N bond formations Many organic compounds containing nitrogen exhibit important biological and pharmaceutical properties. As with gold-catalyzed C–O bond formation, the directly

• . In addition to intermolecular addition, Mukherjee and Widenhoefer recently reported a gold(I)-catalyzed intramolecular amination of allylic alcohols 130 with alkylamines (Scheme 23) [61]. 3.2 Imines as nucleophiles Gold-catalyzed cyclizations of O-propioloyl oximes via C–N bond formation followed by

• the Brønsted acid is both a chiral catalyst for the asymmetric cycloaddition and assists to facilitate the gold complex catalyzed hydroamination. Muratore et al. have reported an interesting example of C–N bond formation for the construction of chiral nitrogen-containing fused heterocycles 400 [191

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• requires fission of three bonds: The propargylic C–N bond in ring expansion; the aryl–aziridinyl C–C bond in the 1,2 shift and the propargylic C–H bond for aromatisation (Scheme 3). The positioning of a deuterium atom at the benzylic carbon in 4 enables the carbons of the aziridine ring to be distinguished

Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

• Václav Jurčík,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

• explored for the hydrogenolysis of 5a, however cleavage of the C–N bond proved very difficult and a satisfactory method could not be found. Therefore, (S)-α-(p-methoxyphenyl)ethylamine (3b) was explored as an alternative amine for the aza-Michael reaction, as removal of this amine using ceric ammonium

C–C (alkynylation) vs C–O (ether) bond formation under Pd/C–Cu catalysis: synthesis and pharmacological evaluation of 4-alkynylthieno[2,3-d]pyrimidines

• Dhilli Rao Gorja,
• K. Shiva Kumar,
• K. Mukkanti and
• Manojit Pal

Beilstein J. Org. Chem. 2011, 7, 338–345, doi:10.3762/bjoc.7.44

• case of MeOH. While triethylamine was used as a base in all these cases, the use of a secondary amine, e.g., pyrrolidine was also examined. A side product was observed in this case due to the C–N bond forming reaction between 1a and pyrrolidine and was identified as 4-(N-pyrrolidinyl)-5,6,7,8

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• specific advantages and disadvantages that should be considered when selecting the reaction conditions for a desired C–N bond formation in the course of a total synthesis or drug synthesis. Keywords: biologically active compounds; boronic acid; copper; N-arylation; palladium; Introduction Palladium- and

α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

• David. M. Hodgson and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2010, 6, 978–983, doi:10.3762/bjoc.6.110

• group undergo cleavage at the formally benzylic C–N bond, leading to α-aminophosphonates. With β-alkyl groups, regioselectivity is influenced by the presence or absence of an N-substituent. N-Ts Cis-β-alkyl-substituted aziridinylphosphonates give β-aminophosphonates [32], whereas both N-Boc cis- and

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

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

• , N3, N5, N6, N7 and N8, from all three strands of the cryptand moiety are protonated, which is evident by the comparatively longer C–N bond distances of these nitrogen atoms with the neighboring carbons (Table 1). The encapsulated perchlorate is involved in two N–H···O and five O–H···O hydrogen

Variations in product in reactions of naphthoquinone with primary amines

• Marjit W. Singh,
• Anirban Karmakar,
• Nilotpal Barooah and
• Jubaraj B. Baruah

Beilstein J. Org. Chem. 2007, 3, No. 10, doi:10.1186/1860-5397-3-10

• -naphthoquinone with 4-aminothiophenol and 1,4-naphthoquinone with 4-aminophenol are compared. The former leads to C-S and the latter to C-N bond formation. The reaction of 1,4-naphthoquinone with 4-aminothiophenol in an NMR tube is studied to explain that 2-(4-anilinothiolato) 1,4-naphthoquinone derivative to be

•  3c). Surprisingly in this reaction the product formed is through C-S bond formation rather than C N-bond formation (Scheme 4). The presence of a few well-separated peaks of the products from the starting materials in the NMR spectra (designated by A) shows the formation of the one product with time

• complete understanding of the mechanism but the observations hint towards a radical mechanism rather than an ionic mechanism. In contrast to the reaction of 4-aminothiophenol with 1,4-naphthoquinone the reaction of 4-aminophenol gave the expected product through C-N bond formation. The structures of the

Molecular recognition. 1. Crystal structures of hexaazamacrocyclic amines containing p-xylylene spacers and their adducts with acids

• Teresa Borowiak,
• Grzegorz Dutkiewicz,
• Maciej Kubicki,
• Marek Pietraszkiewicz,
• Agnieszka Gil and
• Rainer Mattes

Beilstein J. Org. Chem. 2005, 1, No. 16, doi:10.1186/1860-5397-1-16

• symmetry no shift between the centroids of the phenyl rings exists, they are oriented in an antiparallel mode with the angle between their planes of 43.1(1)°. The observed C-N bond lengths range from 1.483(5) to 1.506(5) Å and confirm protonation of all N atoms. Moreover, all the hydrogen atoms at