Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• ; difluoromethyl compounds; fluorinated diazo reagents; strong Brønsted acids; Introduction Chiral aziridines are prevalently found in natural products and artificially made bioactive molecules, thus receiving significant attention in the past decades [1][2][3][4][5][6]. Among them, the introduction of fluorine

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• . Petersburg State University, Universitetskiy pr., 26, Saint Petersburg, Petrodvoretz, 198504 , Russia Department of Chemistry, Saint Petersburg State Forest Technical University, Institutsky per., 5, Saint Petersburg, 194021, Russia 10.3762/bjoc.14.268 Abstract In strong Brønsted acids (CF3SO3H, FSO3H

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• , decreasing in the series t-BuMe2Si > Et3Si > Me3Si. It has been shown that Ir-hydride complexes that are formed as intermediates during hydrogenation are strong Brønsted acids [32], which can cause cleavage of trimethylsilyl ethers under hydrogenation conditions [33]. So partial desilylation liberating a

Lewis acid-catalyzed redox-neutral amination of 2-(3-pyrroline-1-yl)benzaldehydes via intramolecular [1,5]-hydride shift/isomerization reaction

• Chun-Huan Jiang,
• Xiantao Lei,
• Le Zhen,
• Hong-Jin Du,
• Xiaoan Wen,
• Qing-Long Xu and
• Hongbin Sun

Beilstein J. Org. Chem. 2014, 10, 2892–2896, doi:10.3762/bjoc.10.306

• for 24 h gave the trisubstituted amine 3a in 50% yield (entry 1, Table 1). Encouraged by this result, we screened readily available Brønsted and Lewis acids (Table 1). Except the Lewis acid AlCl3, other strong Brønsted acids and common Lewis acids could be used as the catalyst in this reaction

Synthesis of a bifunctional cytidine derivative and its conjugation to RNA for in vitro selection of a cytidine deaminase ribozyme

• Nico Rublack and
• Sabine Müller

Beilstein J. Org. Chem. 2014, 10, 1906–1913, doi:10.3762/bjoc.10.198

• ], the 5'-OH group of tris-silylated nucleosides can be selectively removed by treatment with a THF/TFA/H2O mix (4:1:1, v/v/v) at 0 °C. Since cleavage of Boc-groups requires strong Brønsted acids [37][38][39], we varied the protocol of Zhu et al. with respect to the acid concentration and to reaction

Engineering of indole-based tethered biheterocyclic alkaloid meridianin into β-carboline-derived tetracyclic polyheterocycles via amino functionalization/6-endo cationic π-cyclization

• Piyush K. Agarwal,
• Meena D. Dathi,
• Mohammad Saifuddin and
• Bijoy Kundu

Beilstein J. Org. Chem. 2012, 8, 1901–1908, doi:10.3762/bjoc.8.220

• considered to be an important factor [67] in promoting cationic π-cyclization by enhancing the electrophilicity of the imines, we envisaged that employing stronger acids may facilitate 6-endo cyclization. Accordingly, the amine 2a was treated with 4-chlorobenzaldehyde by using strong Brønsted acids, such as

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• many other Lewis acids including BF3, BeCl2, TiCl4, SbCl5 or SnCl4 have been described as catalysts for the FC alkylation. Furthermore, strong Brønsted-acids including sulfuric acid, hydrofluoric acid or super acids such as HF•SbF5 and HSO3F•SbF5 have also been shown to accelerate this transformation

• catalytic FC benzylations using benzyl alcohols have been developed. These utilize for instance Cl2Si(OTf)2, Hf(OTf)4 [8], Yb(OTf)3, La(OTf)3 [9], InCl3 [10][11], NbCl5 [12], heterobimetallic Ir-Sn-catalysts [13][14], H-mont [15], [CpMoCl(CO)3]/o-chloranil [16], strong Brønsted acids [17][18][19] calix[6

• reaction was subsequently used by other groups for the synthesis of (all-rac)-α-tocopherol 63 (Vitamin E) and its more stable acetate derivative starting from the two precursors trimethylhydroquinone 61 and isophytol 62 [77][78][79]. Strong Brønsted acids as well as various rare-earth metal triflates and