Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• reaction for gram-scale synthesis with a remarkably low catalyst loading of 0.1 mol %. Oxygen plays an important role in the proposed mechanism: it regenerates the catalyst by aerobic oxidation and oxidizes the carbon-centred radical intermediate, obtained by radical addition of a thiocyanate radical to

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• within 30 min (Scheme 4). Excellent stereoselectivity was also achieved with a diastereomeric ratio of 98:2 and enantiomeric ratio up to 99:1. Simple flash column chromatographic purification methods, low catalyst loading, gram scale synthesis, etc. were advantageous for the reaction [52]. Morita–Baylis

An effective Pd nanocatalyst in aqueous media: stilbene synthesis by Mizoroki–Heck coupling reaction under microwave irradiation

• Carolina S. García,
• Paula M. Uberman and
• Sandra E. Martín

Beilstein J. Org. Chem. 2017, 13, 1717–1727, doi:10.3762/bjoc.13.166

• reaction was carried out in a short reaction time and with low catalyst loading, leading to high turnover frequency (TOFs of the order of 100 h−1). The advantages like operational simplicity, high robustness, efficiency and turnover frequency, the utilization of aqueous media and simple product work-up

• bromides with electron-withdrawing groups as coupling partners, such as 4-bromoacetophenone (1a) and 4-bromobenzophenone (1b), the reactions were carried out in short times, employing low catalyst loading, obtaining the (E)-stilbenes 3 and 4 with excellent yields and selectivity (entries 1 and 2, Table 2

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• mild aerobic conditions (Scheme 27). Low catalyst loading was required with a diverse substrate scope. The robustness of the reaction was demonstrated via gram-scale synthesis of the desired product. Recently, an aerobic photooxidative synthesis of quinazoline from 2-aminobenzylamine and aldehyde in

Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

• Anne L. Schöffler,
• Ata Makarem,
• Frank Rominger and
• Bernd F. Straub

Beilstein J. Org. Chem. 2016, 12, 1566–1572, doi:10.3762/bjoc.12.151

• conditions. Our research group has already established molecularly defined dicopper catalysts with unprecedented activity under diluted conditions with low catalyst loading [37][40]. Thus, we aimed at an even more facile synthesis of dicopper complexes with bis-N-heterocyclic carbene ancillary ligands

Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

• Hee Seung Jang,
• Yubin Kim and
• Dae Young Kim

Beilstein J. Org. Chem. 2016, 12, 1551–1556, doi:10.3762/bjoc.12.149

• methanol were used as the solvent (Table 1, entries 7–11). Under low catalyst loading of 2.5 mol %, this enantioselective addition reaction proceeded successfully to give 3a without compromising the reactivity and enantioselectivity (Table 1, entries 3 and 12–14). Finally, lowering the reaction temperature

• low catalyst loading (2.5 mol %). Chiral 3-amino-3-phosphonyl-substituted oxindole derivatives were obtained in high yields and excellent enantioselectivities were observed (up to 99% ee). This reaction affords valuable and easy access to chiral 3-amino-3-phosphonyl-substituted oxindole derivatives

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

• . Compared with the chiral CuOTf/Et3N system, the CuHMDS system showed higher reactivity, and the desired reactions proceeded in high yields and high selectivities with catalyst loadings as low as 0.01 mol %. Keywords: [3 + 2] cycloaddition; asymmetric reaction; catalytic reaction; low catalyst loading

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• group described the first chiral imidodiphosphoric acid-catalyzed enantioselective Friedel–Crafts reactions of indoles and pyrroles with 3-hydroxy-3-indolyloxindoles, giving the 3,3-diaryloxindoles in excellent yields (99% yield) and with excellent enantioselectivities (98% ee) at low catalyst loading

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• reactions were performed at room temperature and low catalyst loading (0.5 mol %) to afford the desired product in high yield and enantioselectivity. To reduce the amount of cyclohexadiene, the reaction was also performed in trifluorotoluene, resulting in a yield decrease (93% when 1,4-cyclohexadiene was

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• reaction with low catalyst loading results in incomplete conversion. Subsequently the catalytic activity of different solvents was tested at a Cu loading of 0.5 mol % (Table 1). Moderate catalytic activities were obtained for DMSO or without solvent. When CH3CN was used, the reaction gave an excellent

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• and Etienne reported a perfluorinated F21-tris(pyrazoly)borate (F21-Tp) scorpionate ligand, which enhanced alkane C–H functionalization by carbene insertion with (F21-Tp)Cu and (F21-Tp)Ag catalysts (Figure 1) [38]. In particular, with silver catalyst remarkably low catalyst loading (ca. 0.5%), and

(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

• dihydropyrans 122. They utilized the novel tyrosine-derived tertiary amine-thiourea 123 in quite low catalyst loading to catalyze the reaction between α-cyanoketones 118 and β,γ-unsaturated α-ketoesters 87 (Scheme 39) [59]. Initially a Michael reaction occurs, followed by a hemiacetalization reaction, providing

• 118 and (E)-1,1,1-trichloro-4-phenylbut-3-en-2-one 148 catalyzed by bifunctional thiourea (R)-120 producing α-trichloromethyldihydropyrans 149 (Scheme 47) [68]. Utilizing a quite low catalyst loading (2 mol %), good yields and selectivities were achieved. In 2011, Lee and co-workers disclosed the

• , Liang, Xu and co-workers developed a domino process in order to construct polysubstituted chromeno[4,3-b]pyrrolidine derivatives 157, utilizing a bifunctional organocatalyst 57 (Scheme 50) [71]. The transformation is quite powerful, utilizing under mild conditions and a very low catalyst loading. The

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• 2nd generation catalyst (33) and a variation of the latter (66, Figure 8) in the RCM of diethyl diallylmalonate (29) [66]. Reactions were performed with very low catalyst loading (from 2.5 to 0.04 mol %), at 30 °C, under air in nondegassed DCM, nondegassed methyl decanoate and under solvent-free

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

• require the addition and/or removal of groups on the Michael acceptor in order to achieve good stereoselectivity, which makes these reactions atom economical. Also, the low catalyst loading allows for the use of a variety of chiral ligands. Herein, various types of ECA reactions are discussed. 2.1 Copper

Synthesis of α-amino amidines through molecular iodine-catalyzed three-component coupling of isocyanides, aldehydes and amines

• Praveen Reddy Adiyala,
• D. Chandrasekhar,
• Jeevak Sopanrao Kapure,
• Chada Narsimha Reddy and
• Ram Awatar Maurya

Beilstein J. Org. Chem. 2014, 10, 2065–2070, doi:10.3762/bjoc.10.214

• amidines. However, it should be emphasized that our protocol with low catalyst loading (1 mol %) makes it a cleaner and lower environmental impact methodology to access α-amino amidines. Then, we tried the three-component reaction using heteroaromatic amines such as 2-aminopyridine, 3-aminopyridine and 4

• access to α-amino amidine and imidazolopyridines in high yield with significantly low catalyst loading. Experimental A 25 mL round bottom flask was filled with aldehyde (1 mmol), amine (2 mmol)/2-aminopyridine (1 mmol), isocyanide (1 mmol) and MeOH (5 mL). Then, I2 (1 mol %) was added and the reaction

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• -pentyrolactone and not the corresponding seven-membered lactone. The primary product from hydroxymethylation was also isolated from the reaction of the ε-keto ester 25 [40]. Heterogeneous and dye-sensitized photocatalysis The results with the semiconductor particle TiO2 P25 under low catalyst loading conditions

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

• linear secondary aliphatic amines, and terminal alkyl/aryl alkynes. It is noteworthy that the reactions occurred under mild conditions with a low catalyst loading. The solvent of choice was methanol (technical grade), but the reaction ran also well in other alcohols and acetonitrile, whereas yields were

• tertiary propargylamines from aldehydes, secondary amines and alkynes was reported by Li and co-workers [19], a bare three months before the work on silver cited above [5]. Both Au(I) and Au(III) salts demonstrated to be effective with low catalyst loading (1 mol %). Surprisingly, water was the solvent of

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

• Pablo Morán-Poladura,
• Eduardo Rubio and
• José M. González

Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249

• dioxane under the sole influence of a relatively low catalyst loading furnishes, consistently, a significant variety of differently substituted chromenes. The selectivity in favor of the 3-iodo-substituted chromene is in all cases of practical significance. In some cases, exclusive formation of the

Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

• Pankaj Chauhan and
• Swapandeep Singh Chimni

Beilstein J. Org. Chem. 2012, 8, 2132–2141, doi:10.3762/bjoc.8.240

• solvent-free conditions by using a planetary ball mill (Scheme 7) [46]. Cinchona-derived chiral squaramide IX, at low catalyst loading of 0.5 mol %, efficiently catalyses the solvent-free Michael reaction of acetylacetone (9) with various substituted nitroalkenes 7 in a short reaction time (5–30 minutes

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• pyrrolidine derivatives XIV (Scheme 20). In 2007 Wang et al. [67] presented a hydrogen-bond-mediated catalysis in order to perform highly enantio- and diastereoselective tandem Michael–aldol reactions for the synthesis of thiochromene derivatives. In a very low catalyst loading (<1 mol %) of hybrid thiourea

A novel asymmetric synthesis of cinacalcet hydrochloride

• Veera R. Arava,
• Laxminarasimhulu Gorentla and
• Pramod K. Dubey

Beilstein J. Org. Chem. 2012, 8, 1366–1373, doi:10.3762/bjoc.8.158

• formation of 14, the reduction was tried to be carried out with 5% Pd/C and simply bubbling hydrogen gas into the reaction mixture at room temperature, and also by reducing the proportion of the catalyst (Table 1). The impurity formation was observed even at low catalyst loading. As a result, the impurity

Enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinones to nitroalkenes catalyzed by binaphthyl-derived organocatalysts

• Saet Byeol Woo and
• Dae Young Kim

Beilstein J. Org. Chem. 2012, 8, 699–704, doi:10.3762/bjoc.8.78

• organocatalysts is described. This reaction afforded the chiral functionalized naphthoquinones in high yields (81–95%) and excellent enantioselectivities (91–98% ee) under low catalyst loading (1 mol %). Keywords: asymmetric catalysis; Michael addition; 1,4-naphthoquinones; nitroalkenes; organocatalysis

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

• alcohols has been developed by utilizing NaAuCl4. The benzylic and secondary alcohols (55 and 58) worked well under mild conditions with low catalyst loading (Scheme 11). The chiral benzyl alcohol 60 gave racemic ether 61, which suggested the intermediacy of a carbocation. Ye et al. reported an expedient

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers

• Berenger Biannic,
• Thomas Ghebreghiorgis and
• Aaron Aponick

Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91

• easily accomplished with monoallylic diol substrates, as illustrated in Scheme 1 [23][24][25]. The reactions are generally rapid and high yielding with low catalyst loading and can be carried out at low reaction temperatures. Additionally, they are stereospecific, as changing the olefin geometry provides

Highly efficient gold(I)-catalyzed Overman rearrangement in water

• Dong Xing and
• Dan Yang

Beilstein J. Org. Chem. 2011, 7, 781–785, doi:10.3762/bjoc.7.88

• substituted allylic trichloroacetamides. This transformation was performed in water under very mild reaction conditions and could be carried out on the gram-scale with low catalyst loading and simple work-up procedure, making it potentially applicable to the industrial community for large-scale synthesis