Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• up to 325 °C. With these sterically hindered iminopyridine–palladium complexes Pd1 to Pd5 in hand, we firstly investigated their catalytic activity directly in Suzuki cross-coupling reactions with chlorobenzene as the electrophile. The reactions were performed under the previously reported conditions

• , entries 13). Different arylboronic acids were also examined to react with 4-chloroacetophenone in this system. No matter what kind of boronic acids were used: electron-deficient (Table 4, entry 14), electron-rich (Table 4, entries 15 and 16) or sterically hindered (Table 4, entry 17) arylboronic acids

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

• Peter H. Seeberger,
• Claney L. Pereira and
• Subramanian Govindan

Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19

• azido group following β-glucoside formation [23]. Alternatively, a linear synthetic strategy in which the sterically hindered C4 hydroxy group would be glycosylated first, followed by the C3 hydroxy group of β-mannosazide building block 4, was designed in case the convergent approach proved unsuccessful

Facile synthesis of indolo[3,2-a]carbazoles via Pd-catalyzed twofold oxidative cyclization

• Chao Yang,
• Kai Lin,
• Lan Huang,
• Wei-dong Pan and
• Sheng Liu

Beilstein J. Org. Chem. 2016, 12, 2490–2494, doi:10.3762/bjoc.12.243

• -position, only one regioisomer 1i was observed. However, the selectivity was reversed when acetyl was present at the meta-position (5:1 for 2j). The main cyclized product of 2j was the corresponding ortho-acetyl product 1j. Unexpectedly, the reaction preferentially occurred at a more sterically hindered

An effective one-pot access to polynuclear dispiroheterocyclic structures comprising pyrrolidinyloxindole and imidazothiazolotriazine moieties via a 1,3-dipolar cycloaddition strategy

• Alexei N. Izmest’ev,
• Galina A. Gazieva,
• Natalya V. Sigay,
• Sergei A. Serkov,
• Valentina A. Karnoukhova,
• Vadim V. Kachala,
• Alexander S. Shashkov,
• Igor E. Zanin,
• Angelina N. Kravchenko and
• Nina N. Makhova

Beilstein J. Org. Chem. 2016, 12, 2240–2249, doi:10.3762/bjoc.12.216

• generated from isatins and sarcosine to benzylidene derivatives of the same imidazothiazolotriazine will proceed from the less sterically hindered side [41] (anti attack). Herein, we report a regio- and diastereoselective one-pot method for the synthesis of a novel class of polynuclear dispiroheterocyclic

Potent triazine-based dehydrocondensing reagents substituted by an amido group

• Munetaka Kunishima,
• Daiki Kato,
• Nobu Kimura,
• Masanori Kitamura,
• Kohei Yamada and
• Kazuhito Hioki

Beilstein J. Org. Chem. 2016, 12, 1897–1903, doi:10.3762/bjoc.12.179

• nucleophilic aniline 2b (Table 2, entry 2). To elucidate the reactivities of X and DMT-MM, time courses of amide-forming reactions using sterically hindered pivalic acid (1b) and 2-phenylethylamine (2a) in MeOH and THF were investigated by 1H NMR spectroscopy (Figure 2a,b, respectively). The steric hindrance

• the stability and non-hygroscopic property of the reagent (Table 2). In most cases, X exhibited similar reactivity in MeOH compared with DMT-MM, and the amides 3 were obtained with negligible formation of the corresponding methyl ester 8 (Table 2, entries 1, 5, 7, and 9). In the case of the sterically

• hindered secondary amine 2c, methyl ester 8 was obtained as a byproduct in 31% and 24% yields for X and DMT-MM (Table 2, entry 3), respectively. In contrast, the yields obtained in THF using X were superior to those obtained using DMT-MM (Table 2, entries 4, 6, 8, and 10), especially for the poorly

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• as the result of imine oxidation and aryl migration. On the other hand, electron-withdrawing substituents on the aryl group (Ar) promote the formation of amides 119d–f as result of hydride migration. The sterically hindered and fully substituted pyrrole 120 underwent a Baeyer–Villiger reaction to

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

• Carl J. Mallia,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

Development of chiral metal amides as highly reactive catalysts for asymmetric [3 + 2] cycloadditions

• Yasuhiro Yamashita,
• Susumu Yoshimoto,
• Mark J. Dutton and
• Shū Kobayashi

Beilstein J. Org. Chem. 2016, 12, 1447–1452, doi:10.3762/bjoc.12.140

•  2, entries 5–9). Sterically hindered substrates were also viable, and high enantioselectivities were obtained with 0.01 mol % catalyst loading (Table 2, entries 10–13). Other electrophiles were also successfully employed with 0.1 mol % catalyst loading (Scheme 1). N-Methylmaleimide reacted with 1a

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• furnished 96 in high yield and enantioselectivity (Scheme 23a) [24]. Thiols also added efficiently to itaconimide 95 using the same guanidine catalyst system. In general, sterically hindered tertiary thiols added with higher enantioselectivity (85.5:14.5 to 88:22 er) than aromatic thiols (72:28 to 79.5:20.5

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• function in a sterically hindered and electronically unreactive Cbz-protected amine substrate, which is in agreement with our observations above. Therefore, we decided to continue our route with the free amine 36 instead, which was directly coupled with TSNCO to give 39 in high yield. The reaction took

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• groups, as well as sterically hindered aromatic rings, all taking place at room temperature. Suzuki–Miyaura-type C–H coupling reactions are typically more tolerant of electron-withdrawing groups (3d, 3f, 3k) and ortho-substitution (3g) on the aryl ring. On the other hand, the reaction with 4

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• sterically hindered catalyst such as Rh2(esp)2 or Rh2(OPiv)4 is needed to prevent dimerization of the diazoacetate. These catalysts are presumed to protect the carbene intermediates from intermolecular reactions long enough to adopt the correct conformation for bridged-ring formation. An exploration of the

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki–Miyaura cross-coupling reaction

• Dariusz Błachut,
• Joanna Szawkało and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2016, 12, 835–845, doi:10.3762/bjoc.12.82

• derivatives 46–56, in a yield range of 82–91%, in less than 1 h, with exception of 48 (68%) and 52 (62%). In these cases the use of sterically hindered and less reactive 2-trifluorophenylboronic acid needed a longer reaction time of 3 hours and an increased arylboronic acid/substrate ratio. In order to obtain

Stereoselective amine-thiourea-catalysed sulfa-Michael/nitroaldol cascade approach to 3,4,5-substituted tetrahydrothiophenes bearing a quaternary stereocenter

• Sara Meninno,
• Chiara Volpe,
• Giorgio Della Sala,
• Amedeo Capobianco and
• Alessandra Lattanzi

Beilstein J. Org. Chem. 2016, 12, 643–647, doi:10.3762/bjoc.12.63

• catalysts (I–VII). Among the catalysts tested, compound VII proved to be the most active and enantioselective, giving the major diastereoisomer 7a with 44% ee (Table 1, entry 13). Taking into account that amine thiourea VII, bearing a sterically hindered secondary amine moiety, was significantly more

Studies on the synthesis of peptides containing dehydrovaline and dehydroisoleucine based on copper-mediated enamide formation

• Franziska Gille and
• Andreas Kirschning

Beilstein J. Org. Chem. 2016, 12, 564–570, doi:10.3762/bjoc.12.55

• without scrambling of stereochemistry. In summary, we showed that the C–N coupling reaction is a powerful tool to straight forwardly build-up of sterically hindered dehydroamino acid-containing peptide fragments. Selected examples of oligopeptides bearing dehydroamino acid moieties: myxovalargin (1

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• proceeded in good to excellent yield and excellent enantioselectivity for almost all of the substrates that were tested. This methodology was further extended in the total synthesis of (−)-mesembrine. This natural product contains a sterically hindered and arylated quaternary carbon center, which was

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 117–124, doi:10.3762/bjoc.12.13

• reveals a quadrant highly sterically hindered (37.2) due to the rotation of the aromatic ring on the NHC which facilitates the allocation of such a NHC ligand in the dinuclear complexes. The other quadrant where this aromatic ring participates displays a value of 29.2, whereas the other two are innocuous

• species. Steric maps confirm that the H-T is preferred since the metal centres are less sterically hindered, thus revealing the relatively unstable kinetic H-H isomers with respect to the H-T ones. However, screening the evolution from complex 3 to 6, going through complexes 4 and 5, the relative

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• hydrogel reforms. Irradiation at 335 nm causes trans-4,4’-azobenzene carboxylate to photo-isomerize to the cis isomer which is too sterically hindered to form a stable α-CD complex, and the dodecyl substituents of PAAddn are once again complexed by α-CD and the hydrogel disaggregates. This last step is

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