Synthesis of α,β-unsaturated esters via a chemo-enzymatic chain elongation approach by combining carboxylic acid reduction and Wittig reaction

• Yitao Duan,
• Peiyuan Yao,
• Yuncheng Du,
• Jinhui Feng,
• Qiaqing Wu and
• Dunming Zhu

Beilstein J. Org. Chem. 2015, 11, 2245–2251, doi:10.3762/bjoc.11.243

• to the sterically hindered effect of the α-methyl substitution, which is consistent with the results for Pyrococcus furiosus (whole-cell) [36] and NiCAR [31]. However, no significant difference was noted between 3-phenylbutyric acid (15a) and 7a. Mycobacterium CAR showed good chemoselectivity for the

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• on the hindered benzylidene. With more sterically hindered amines b–d, the ruthenium complexes 11b–d, resulting from phosphine displacement, proved to be stable even after 24 h at 60 °C (Scheme 4). The half-life of methylidene 2 derived from GII in the presence of the amines were then evaluated using

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• leads to the formation of polycyclic isoquinoline derivatives [29] and the reaction of 3,5-di(tert-butyl)-1,2-benzoquinone with 1,2,3-trimethyl-benzimidazolium salts gives rise a spirocyclic derivative of sterically hindered pyrocatechol [30]. The structures of the prepared 2-hetaryl-1,3-tropolones have

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• suppose that this reaction can be sterically hindered by the bulky structure of a norbornene monomer unit. During the cross-metathesis, [Ru]=PNB carbenes exist at a low concentration but their presence is crucial for the course of the whole process. For developing the cross-metathesis as a new method of

A facile synthetic route to benzimidazolium salts bearing bulky aromatic N-substituents

• Gabriele Grieco,
• Olivier Blacque and
• Heinz Berke

Beilstein J. Org. Chem. 2015, 11, 1656–1666, doi:10.3762/bjoc.11.182

• synthesis for the sterically hindered benzimidazolium salts: 1,3-bis(2,4,6-trimethylphenyl)-1H-benzo[d]imidazol-3-ium chloride (1-Cl) [42][43], 1,3-bis(2,6-diisopropylphenyl)-1H-benzo[d]imidazol-3-ium chloride (2-Cl), 1,3-diphenyl-1H-benzo[d]imidazol-3-ium chloride (3-Cl) [44][45] and 1,3-di(pyridin-2-yl

Qualitative evaluation of regioselectivity in the formation of di- and tri-6-O-tritylates of α-cyclodextrin

• Keisuke Yoshikiyo,
• Yoshihisa Matsui and
• Tatsuyuki Yamamoto

Beilstein J. Org. Chem. 2015, 11, 1530–1540, doi:10.3762/bjoc.11.168

• was separated and characterized [18]. The trityl group is so bulky that the additional tritylation of C(6)-OH on Glu adjacent to a previously tritylated Glu is considered to be sterically hindered. Thus, a reaction of α-CD with 3.3 equivalents TrCl in pyridine at 55 °C gave selectively the ACE-isomer

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• , sterically not hindered alkene like 1-decene (Table 3, entry 1) still gave reasonable yields of the addition product. The yield is lower in addition to norbornene and cyclooctene, both of which are more sterically hindered and do not allow any mesomeric stabilization of the intermediate radical (Table 3

• ), 91 (93) [C7H7+], 65 (43) [C5H5+]; HRMS (ESI) m/z: [M + Na]+ calcd for C14H22N35ClO3S + Na 342.0901; found, 342.0890; C14H22N37ClO3S + Na [M + Na]+: 344.0874; found, 344.0864. Preparation of the chloroamides. First experiments for the intermolecular radical addition. Reaction of sterically hindered N

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• sterically hindered pyrrole-H. The highest yielding reactions under sealed tube conditions gave comparable yields to the lowest yielding reactions under microwave conditions. In general, the microwave conditions give high yields and can tolerate a range of functional groups on the aryl halide. We believe

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• the auxiliary that locked the conformation of the molecule. The excess Grignard reagent would add to the double bond from the less sterically hindered side, thus leading to the diastereoselectivity. Note that when using Grignard reagents as nucleophiles in CA reactions, the possibility of the 1,2

Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• synthesis of novel polycyclic compounds. Further, we report for the first time the synthesis of derivatives of these heterocycles, including those using the sterically hindered allyl reagents with terminal methyl substituents. The allylation reaction also provides access to new hydroxylated heterocyclic

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• -electron transfer and then a nucleophile (acetate) is added to this intermediate, preferentially from the less sterically hindered α-side. An interesting product of the electrochemical oxidation of cholesterol [39], i.e. dicholesteryl ether 18, was obtained in 28% yield during the electrolysis carried out

An unusually stable chlorophosphite: What makes BIFOP–Cl so robust against hydrolysis?

• Roberto Blanco Trillo,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2015, 11, 313–322, doi:10.3762/bjoc.11.36

• intramolecular palladium-catalyzed alkyl–aryl cross-coupling reaction [13] and in Pd-catalyzed allylic substitutions [14]. Several of the highly sterically hindered BIFOP derivatives were employed as ligands in Cu-catalyzed 1,4-additions [15]. Similar chelating fencholates [16][17][18][19][20][21][22] (Scheme 1

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• . Electron-withdrawing and electron-donating groups as well as sterically hindered aryl substituents are also accepted (see Table 1, entries 7 and 9). The use of buta-1,3-diene and 2,3-dimethyl-1,3-butadiene gave the 1,4-dienols in excellent yields (Table 1, entries 12 and 13). When isoprene was used, the

One-pot functionalisation of N-substituted tetrahydroisoquinolines by photooxidation and tunable organometallic trapping of iminium intermediates

• Joshua P. Barham,
• Matthew P. John and
• John A. Murphy

Beilstein J. Org. Chem. 2014, 10, 2981–2988, doi:10.3762/bjoc.10.316

• was also observed (the ratio of 6aj:7a:4a = 5:3:1). However, our observations cannot rule out β-hydride addition as the first step. Consistent with our observations, the authors report that the more sterically hindered 2-methylallylzinc and 2-butenylzinc halides do not dimerise even after 48 h under

Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

• Sambasivarao Kotha and
• Mirtunjay Kumar Dipak

Beilstein J. Org. Chem. 2014, 10, 2664–2670, doi:10.3762/bjoc.10.280

• caged systems. At the same time non-participation of 24 in the RRM reaction reveals that systems which contain a sterically hindered cyclohexene ring are not suitable candidates for the tandem metathesis sequence. Experimental General Reactions involving organometallic species were carried out under

Selenium halide-induced bridge formation in [2.2]paracyclophanes

• Laura G. Sarbu,
• Henning Hopf,
• Peter G. Jones and
• Lucian M. Birsa

Beilstein J. Org. Chem. 2014, 10, 2550–2555, doi:10.3762/bjoc.10.266

• previously reported investigations on the mechanism of the reaction of phenylselenyl chloride with selected sterically hindered alkenes [29], the most probable mechanism involves, in a first step, the addition of one equivalent of PhSeCl to one of the triple bonds of 1 resulting in the formation of

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• reaction product. The base precursor should be more easily electroreduced than the weakly acidic hydrocarbon group and carbon dioxide, and should not undergo a nucleophilic attack by either the hydrocarbon anion or the electrogenerated base. Therefore, the base precursor should be sterically hindered at or

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• to prevent the coordination of a second phosphorus atom [13][14] or cavity-shaped phosphines [15]. The use of sterically-hindered P(III)-derivatives, notably phosphites [16][17][18][19][20][21], has also proven beneficial in yet another carbon–carbon forming reaction, namely the rhodium-catalysed

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units

• Aurica Farcas,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert,
• Flavian Farcas,
• Iuliana Stoica and
• Anton Airinei

Beilstein J. Org. Chem. 2014, 10, 2145–2156, doi:10.3762/bjoc.10.222

• of approaches were examined, e.g., copolymerization [7][8][9][10][11], end-capping with sterically hindered groups [12], introduction of donor (D) and acceptor (A) moieties, to form statistically [13][14] or alternating D–A units in the main chain [15][16][17][18]. The coupling of D–A units has been

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• proposed that the major enantiomer formed through re-face attack of the ylide onto the Michael acceptor, rather than attack from the sterically hindered si-face. 2.16 Michael additions Asymmetric Michael addition is one of the most studied enantioselective processes in organic synthesis, with many

Postsynthetic functionalization of glycodendrons at the focal point

• Thisbe K. Lindhorst and
• Katharina Elsner

Beilstein J. Org. Chem. 2014, 10, 1482–1487, doi:10.3762/bjoc.10.152

• -configured alkenes were the only cross-coupling products obtained. This might be due to the specific structure of the used substrates, as sterically hindered olefins are known to enhance trans-selectivity in metathesis [12]. The same reactions were successful with the tetravalent glycodendron 9 yielding the

A complete series of 6-deoxy-monosubstituted tetraalkylammonium derivatives of α-, β-, and γ-cyclodextrin with 1, 2, and 3 permanent positive charges

• Martin Popr,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2014, 10, 1390–1396, doi:10.3762/bjoc.10.142

• in dry DMF would result in the product substituted on both nitrogens, but unfortunately the MS spectra revealed that only one nitrogen atom gets substituted. We tried different conditions (up to 50 equivalents of 24, different sterically hindered bases, higher temperature) to achieve a conversion

• step, the installed triamine was quaternized by methylation with MeI. To achieve a full conversion, the use of a sterically hindered base was necessary. First, we attempted to methylate intermediate 27 containing a diethylenetriamine moiety. Different bases (K2CO3, 2,6-lutidine, 2,4,6-collidine and DBU

Synthesis of chiral N-phosphoryl aziridines through enantioselective aziridination of alkenes with phosphoryl azide via Co(II)-based metalloradical catalysis

• Jingran Tao,
• Li-Mei Jin and
• X. Peter Zhang

Beilstein J. Org. Chem. 2014, 10, 1282–1289, doi:10.3762/bjoc.10.129

• activating the phosphoryl azide (Figure 1). Further studies showed that the Co(II) complex of the more sterically hindered amidoporphyrin ligand [Co(P2)] (P2 = 2,6-DiMeO-ChenPhyrin) gave almost no reaction (Table 1, entry 6), signifying the steric demand of the catalytic process. Gratifyingly, [Co(P3)], in

• reaction of the sterically hindered substrate o-trifluoromethylstyrene (1e) (Table 2, entry 5). When p-trifluoromethylstyrene (1f) was used as the substrate, however, a decrease in reaction yield was observed (Table 2, entry 6). Furthermore, [Co(P6)] could effectively catalyze the aziridination reactions

Synthesis of 1-[bis(trifluoromethyl)phosphine]-1’-oxazolinylferrocene ligands and their application in regio- and enantioselective Pd-catalyzed allylic alkylation of monosubstituted allyl substrates

• Zeng-Wei Lai,
• Rong-Fei Yang,
• Ke-Yin Ye,
• Hongbin Sun and
• Shu-Li You

Beilstein J. Org. Chem. 2014, 10, 1261–1266, doi:10.3762/bjoc.10.126

• , with our catalytic system, substrates bearing electron-withdrawing groups were well tolerated with excellent regioselectivity and preferred formation of the branched products (b/l: 93/7–99/1, entries 8–10, and 13, Table 2). Reactions of sterically hindered 1-naphthyl allyl carbonate, 2-MeO and 2-Me

Stereocontrolled synthesis of 5-azaspiro[2.3]hexane derivatives as conformationally “frozen” analogues of L-glutamic acid

• Beatrice Bechi,
• David Amantini,
• Cristina Tintori,
• Maurizio Botta and
• Romano di Fabio

Beilstein J. Org. Chem. 2014, 10, 1114–1120, doi:10.3762/bjoc.10.110

• ). Then, a systematic study of the reactivity of compound 17 was undertaken to identify the most efficient method to introduce the cyclopropane ring on the sterically hindered, α,β-unsaturated trisubstituted olefin group. With this goal in mind, both the Corey–Chaykovsky [25][26][27] and the Simmons–Smith