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

• phosphanes of otherwise comparable substitution pattern. The combination of phosphanes with unusually strained cyclic substituents such as diamandoids or cyclophanes also appears to have no particularly unusual effects. Phosphanes with strongly electron-withdrawing substituents such as PF3 (303) have the

• than the one in amines. This implies that phosphanes have a more pyramidal structure than amines with a comparable substitution pattern. The least pyramidal structure is found here for triphenylamine, which is almost perfectly planar at the nitrogen atom. The degree of planarity correlates well with

• the character of the lone pair orbital. In amines the contribution of the s orbital is decreasing with increasing size of the substituents. This is different for phosphanes, where the lone pair orbital has a systematically larger s-character, which depends only marginally on the substitution pattern

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

• rotation around the amide C–N moiety (partial double-bond character) in the NMR as seen by twin peaks in certain cases [25]. In carbamates 10, the substitution pattern α to the C=O group in 7–9 has shifted to the α-position next to the amino center. Therefore, in this strategy (Scheme 2) the enolate

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part II: Iridomyrmecins

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• between the methyl group at C-7 and the substitution pattern at C-7a and C-4a, respectively) configured iridomyrmecins. Key steps were two stereoselective hydrogenations: A transfer hydrogenation for a formal “anti” delivery of hydrogen [14][15], as represented in 5, and the use of Crabtree’s catalyst in

Synthesis of a library of tricyclic azepinoisoindolinones

• Bettina Miller,
• Shuli Mao,
• Kara M. George Rosenker,
• Joshua G. Pierce and
• Peter Wipf

Beilstein J. Org. Chem. 2012, 8, 1091–1097, doi:10.3762/bjoc.8.120

• place during and after the RCM reaction (see below). We also briefly studied the influence of the diene substitution pattern on the rate of isomerization from 4 to 3 and the corresponding product distribution (Scheme 3). Addition of in situ prepared vinyl alane to pivaloate 1 provided the diene 7 in 80

• presence of the Lewis acidic additive Ti(OiPr)4 as well as the substitution pattern of the α,ω-diene precursor. With alkene 3 and the corresponding epoxide 5 in hand, a ZnI2-mediated amine alkylation protocol could be employed, which introduced a variety of nitrogen nucleophiles 8{1–13} (Scheme 4) [38][39

• –isomerization sequence and a ZnI2-mediated epoxide aminolysis. We investigated the factors influencing the alkene isomerization during the RCM process, and identified the presence of the additive Ti(OiPr)4, the substitution pattern on the alkene, and the chemical reactivity of the benzylic allylic methine

Synthesis and anion recognition properties of shape-persistent binaphthyl-containing chiral macrocyclic amides

• Marco Caricato,
• Nerea Jordana Leza,
• Claudia Gargiulli,
• Giuseppe Gattuso,
• Daniele Dondi and
• Dario Pasini

Beilstein J. Org. Chem. 2012, 8, 967–976, doi:10.3762/bjoc.8.109

• most sensitive to variations in the substitution pattern (and thus, in the electronic structure) within the naphthyl systems of the binaphthyl units. The UV–vis spectra of macrocycles (R,R)-10 and (R,R)-11, recorded in solvents possessing different solvating and hydrogen-bonding abilities (CH2Cl2, EtOH

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

• Gehad Zeyat and
• Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

• the lower reactivity of the diazene unit in this thioester owing to the meta-substitution pattern. The ligation reaction of 3,4'-AMPB thioester 1b with the 4,5,6-trimethoxy-2-mercaptobenzyl auxiliary peptide 5 furnished ligation peptide 12 in 38% yield (Table 1, entry 3). In this case, no hydrazine

Synthesis and characterization of Sant-75 derivatives as Hedgehog-pathway inhibitors

• Chao Che,
• Song Li,
• Bo Yang,
• Shengchang Xin,
• Zhixiong Yu,
• Taofeng Shao,
• Chuanye Tao,
• Shuo Lin and
• Zhen Yang

Beilstein J. Org. Chem. 2012, 8, 841–849, doi:10.3762/bjoc.8.94

• smoothly in toluene with NaOt-Bu as base by using a Pd2(dba)3/rac-BINAP catalysis system [50]. Substituent-modifications on the motif D It has previously been shown that the substitution pattern on the nitrogen atom of trans-1,4-diaminocyclohexane moiety plays a critical role in the activity of 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

• quaternary carbon atoms in the 13C NMR spectrum evidenced the presence of the pyrrole structure. Finally, the HMBC experiment proved the proposed substitution pattern at the pyrrole ring. HRMS and elemental analysis allowed identification of 5 as a 2,3,4,5-tetrasubstituted pyrrole derivative. As shown in

Alkoxide-induced ring opening of bicyclic 2-vinylcyclobutanones: A convenient synthesis of 2-vinyl-substituted 3-cycloalkene-1-carboxylic acid esters

• Xiufang Ji,
• Zhiming Li,
• Quanrui Wang and
• Andreas Goeke

Beilstein J. Org. Chem. 2012, 8, 650–657, doi:10.3762/bjoc.8.72

• rings, the substitution pattern on the ring, and the properties of the reagents as well as the reaction conditions. In particular, the ring opening of certain fused-ring cyclobutanones, which are easily prepared by the well-established [2 + 2] cycloadditions of ketenes with various cycloalkenes, has

Cyanoethylation of the glucans dextran and pullulan: Substitution pattern and formation of nanostructures and entrapment of magnetic nanoparticles

• Kathrin Fiege,
• Heinrich Lünsdorf,
• Sevil Atarijabarzadeh and
• Petra Mischnick

Beilstein J. Org. Chem. 2012, 8, 551–566, doi:10.3762/bjoc.8.63

• spectroscopy (PEELS). Keywords: cyanoethyldextran; cyanoethylpullulan; ferromagnetic nanoparticles; glycan nanostructures; substitution pattern; Introduction Cyanoethylation has been widely applied to polysaccharides, e.g., to cellulose [1], inulin [2], and starch [3]. Onda reported on cyanoethylation of

• in our cyanoethylation studies. Cyanoethylglucans of different DS values were produced. Another objective of our approach was the detailed determination of the substitution pattern on the monomer level. Furthermore, nanostructuring of highly substituted cyanoethylglucans with and without

• assign and integrate all relevant resonance signals. This is obvious from the differences obtained when employing different signals for the calculation (Equation 1 and Equation 3). Only after depolymerization it was possible to determine the detailed substitution pattern by GLC analysis. In general, good

On the control of secondary carbanion structure utilising ligand effects during directed metallation

• Andrew E. H. Wheatley,
• Jonathan Clayden,
• Ian H. Hillier,
• Alison Campbell Smith,
• Mark A. Vincent,
• Laurence J. Taylor and
• Joanna Haywood

Beilstein J. Org. Chem. 2012, 8, 50–60, doi:10.3762/bjoc.8.5

• single ortho substituent [25]. At ambient temperature, amides with this substitution pattern are conformationally mobile about their aryl–CO bond [26] on a timescale of seconds or less, and hence, inseparable into atropisomers [27]. However, at the temperatures commonly used to effect lithiation

Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride

• Sergio Pascual,
• Christophe Bour,
• Paula de Mendoza and
• Antonio M. Echavarren

Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178

• have already been synthesized by palladium-catalyzed arylation reactions [53][54]. Strategically halogenated decacyclenes with a substitution pattern similar to that of 2 have been used for the synthesis of circumtrindene by flash vacuum pyrolysis [55]. Here we report the results on the synthesis of

Ugi post-condensation copper-triggered oxidative cascade towards pyrazoles

• Aurélie Dos Santos,
• Laurent El Kaim,
• Laurence Grimaud and
• Caroline Ronsseray

Beilstein J. Org. Chem. 2011, 7, 1310–1314, doi:10.3762/bjoc.7.153

• pyrazolidinone under oxidative conditions from simple hydrazone derivatives (Scheme 1) [13]. The cascade features a [3 + 2] cycloaddition coupled with an aerobic oxidation of the resulting pyrazolidine. A further oxidative coupling may be observed according to the substitution pattern of the starting acyl

Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• product despite the isolation of 6. To establish the complete constitution of an in situ reaction mixture, it was treated with iodine, the crude 1H NMR spectrum (Figure 6) revealing that while much of the ortho- and para-substitution pattern is retained, a small portion of these zincated aryl molecules

A practical route to tertiary diarylmethylamides or -carbamates from imines, organozinc reagents and acyl chlorides or chloroformates

• Erwan Le Gall,
• Antoine Pignon and
• Thierry Martens

Beilstein J. Org. Chem. 2011, 7, 997–1002, doi:10.3762/bjoc.7.112

• should thus serve as valuable precursors in the preparation of compounds of pharmaceutical interest. Several procedures enabling the construction of the diarylmethylamide and -carbamate core have been described. However, with respect to the substitution pattern of the expected final compound, available

• strategies, mainly intended to withdraw electrons and render the carbon more electrophilic [3][4][5][6][7]. Depending on the substitution pattern of the expected final amines, the increase of the electrophilicity should be implemented through the use of activated imines (Scheme 1, pathway A) or by

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• tautomerization. In some cases we observed the formation of minor amounts of 4-hydroxypyridines along with the β-ketoenamides. Depending on the substitution pattern of the β-ketoenamide, a condensation to the corresponding pyridine can spontaneously occur. In most cases a second step is necessary and the

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

• gold-catalyzed cyclization of alk-4-yn-1-ones 79 depending on the substitution pattern in the substrate and the reaction solvent. Thus, alkynones with one substituent at C-3 undergo a 5-exo-dig cycloisomerization to yield substituted furans 81, whilst substrates bearing two substituents at C-3 undergo

Gold(I)-catalyzed formation of furans by a Claisen-type rearrangement of ynenyl allyl ethers

• Florin M. Istrate and
• Fabien Gagosz

Beilstein J. Org. Chem. 2011, 7, 878–885, doi:10.3762/bjoc.7.100

• strongly suggested that no allyl cation was formed during the reaction. The substitution pattern of the pyrroles thus obtained point toward the involvement of a more concerted aza-Claisen-type rearrangement mechanism (2 → 3) and tend to exclude the possibility of a simple N to C allyl shift (2 → 4 → 5

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• ][83]. With an appropriate substitution pattern, both 1,5- and 1,6-enynes can be transformed into a broad array of product scaffolds. The corresponding electrophilic transformations are far less developed. With the exception of an early report by Barluenga and co-workers [84], iodonium-induced

• -migration as an additional step (Scheme 14). Gold-induced activation of the alkyne followed by cyclization produces a cyclopropyl gold carbene 50 as the key intermediate. Depending on the substitution pattern, two alternative reaction outcomes are possible: The formation of bicyclo[3.1.0]hexane derivatives

• dependent on the substitution pattern and configuration of the enyne and leds to variable product formation. For example, Kozmin and co-workers showed in 2006 that 1,5-enynes can also rearrange to 1,3-cyclohexadienes through a series of 1,2-alkyl shifts (Scheme 15) [112]. In particular, when silyloxy enynes

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• substituent in different positions (o-, m-, and p-) relative to the alkyne (acetamides in Figure 4). Such variations in the substitution pattern are known to impose significant effects on photochemical reactivity [56][57]. Reactions with cyclohexadiene were used to probe the properties of the triplet excited

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• setting of the reaction conditions (modulation of the electronic properties of the ligands, counter ion, solvent, substitution pattern of the substrates, etc.). Herein, we report our efforts to control the two competing pathways in the evolution of gold-carbenoid intermediates generated by an initial 1,2

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• organogold species. By contrast, those ligands that increase gold-to-C1 back π-donation or decrease C1-to-gold σ-donation will induce a shorter C1–Au bond and a carbene-like reactivity (Scheme 4) [17]. These studies highlighted the tremendous influence of the substitution pattern and the ancillary ligand on

• , depending on the substitution pattern [35][36]. Due to their high strain and π-electron density, cyclopropenes exhibit reactivity often comparable to that of alkynes in transition metal-catalyzed reactions. Not surprisingly, the reactivity of cyclopropenylmethyl carboxylates in the presence of gold

• ) carbenoid complexes, Toste et al. highlighted the importance of the substitution pattern and the ligands (Scheme 4). Interestingly, DFT calculations were carried out for organogold species that can actually be generated by ring-opening of cyclopropenes, and therefore the authors examined experimentally the

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• ruled out due to the intrinsic selectivity of the reaction. There are two distinct regioselectivities involved in the meta photocycloaddition. The first is with regard to the substitution pattern on the aromatic ring. The influence of electron donating and electron withdrawing substituents on the

• exposure to light but, depending on the substitution pattern, other reactive sites may be involved. Carbonyl groups are also known to undergo different types of photochemistry. Thus, benzophenones, acetophenones and benzaldehydes are not only used as sensitizers but can, under specific circumstances, also

• photocycloaddition of allenylated salicylaldehydes affords a benzoxepine derivative and an apparent para photocycloadduct (Scheme 40) [104]. The product distribution is dependent on the substitution pattern of the aromatic core. Introduction of bulky tert-butyl substituents at positions 3 and 5 on the aromatic ring

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• by the selective preorganization of the substrates by hydrogen bonding between neutral organic functionalities with an appropriate substitution pattern or by complexation of crown-ether units to cationic guest molecules [1][2][3]. In contrast, the selective anion recognition has not been employed

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• o-, m- and p-bis(3-pentynyloxymethyl)benzenes 17 (Table 3). While the cyclic product 16 was obtained from 15 in high yield (95%), different selectivities toward the formation of monomeric [10]cyclophanes 18 and [10.10]cyclophanes 19 depending on the substitution pattern were observed [77]: The