Unnatural α-amino ethyl esters from diethyl malonate or ethyl β-bromo-α-hydroxyiminocarboxylate

• Eloi P. Coutant,
• Vincent Hervin,
• Glwadys Gagnot,
• Candice Ford,
• Racha Baatallah and
• Yves L. Janin

Beilstein J. Org. Chem. 2018, 14, 2853–2860, doi:10.3762/bjoc.14.264

• phase transfer catalyst. For instance, (note b in Table 2), stirring a 1:1.1 proportion of compounds 47 and 48af, sodium carbonate, and 0.01 equiv tetrabutylammonium bromide in toluene for 1.5 hours led to a 42% yield of the α-hydroxyimino ester 2af. On the other hand, such catalysis was not required

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• in the presence of catalyst PTC (3). The designed synthesis is shown in Scheme 3. Two key reactions are included in this novel strategy: 1. the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone (2) with chloroacetonitrile generate 4 through the use of a phase-transfer catalyst; and 2. the

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• phase-transfer catalyst was recently reported [25]. We have published a communication that describes the continuous mixing of aqueous NaOCl and an organic solution of secondary amine, using either a tubular reactor with in-line static mixers or a single stage CSTR [26]. The reactor was selected to

• procedure is not straightforward, requiring multiple unit operations. To avoid this, a phase-transfer catalyst (TBAB) was used along with NaOH (Table 4, entries 7–9). This reagent, in a toluene/water mixture, promoted full conversion to imine 19 (Table 4, entry 8). The separation of the toluene phase

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• asymmetric phase-transfer catalysis based on inherently chiral calix[4]arenes, although the asymmetric induction observed remained moderate. Su et al. demonstrated a new approach for the design of a chiral binary integrative phase-transfer catalyst consisting of p-tert-butylcalix[4]arene and a cinchonine

• ammonium salt [38] (Scheme 2). Due to the failure of obtaining monobromo p-tert-butylcalix[4]arene derivative 6 directly from p-tert-butylcalix[4]arene using 1,2-dibromoethane in the presence of several bases, the synthetic route to calixarene-based chiral phase-transfer catalyst 7 comprises a four-step

• sequence including protection/deprotection steps for the benzyl groups. The catalytic efficiency of calix[4]arene-based phase-transfer catalyst 7 was evaluated in the benchmark reaction (Scheme 3) and compared with that of the chiral quaternary ammonium salt 8. The results obtained when 7 used as

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• catalyzed by a phase-transfer catalyst [74]. Their previous findings on the same reaction using a Cinchona-based phase-transfer catalyst [75] was further improved by using Maruoka’s binaphthyl-derived ammonium salt 110. The formation of intermediate 112 (chiral catalyst still attached to the substrate) from

• oxylation of ketones reported by Masson et al. α-Fluorination of β-keto esters. Alkynylation of β-ketoesters and amides catalyzed by phase-transfer catalyst. Alkynylation of β-ketoesters and dearomative alkynylation of phenols. Acknowledgements The authors highly acknowledge the financial assistance

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• . Currently, the Heck reaction is usually carried out by adding an excess of phase-transfer catalyst such as tetrabutylammonium bromide (TBAB) or tetrabutylammonium iodide (TBAI) to increase the reaction yield under both solvent-heating [19][20][21][22][23] and solvent-free conditions [24][25][26][27

AuBr₃-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

• Jayashree Rajput,
• Srinivas Hotha and
• Madhuri Vangala

Beilstein J. Org. Chem. 2018, 14, 682–687, doi:10.3762/bjoc.14.56

• ], glycoconjugates [30][31][32], N-glycosyl heterocycles [33][34], N-glycosyl triazole [35][36], etc. Glycosyl azides can be accessed from the corresponding glycosyl halides [37][38][39][40] by nucleophilic displacement with NaN3 or using trimethylsilyl azide in the presence of a phase transfer catalyst [41][42][43

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• intramolecular aza-Michael reaction by means of both a chiral auxiliary and a catalyst for stereocontrol is reported for the synthesis of optically active isoindolinones. A selected cinchoninium salt was used as phase-transfer catalyst in combination with a chiral nucleophile, a Michael acceptor and a base to

• intramolecular aza-Michael reaction of acrylamide (R)-24 was then performed using the best phase-transfer catalyst 18c and the optimized experimental conditions to give isoindolinone (2R,3S)-25 as a mixture of diastereoisomers (82% yield, 71% de) which were separated by chromatography and purified by

• -transfer catalyst; 3-substituted isoindolinones; Introduction Isoindolinones I (Figure 1), e.g., 2,3-dihydro-1H-isoindol-1-ones, also called phthalimidines are bicyclic lactams whose molecular structure is the basis of a wide range of alkaloids and biologically active compounds [1][2][3][4][5][6][7][8][9

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

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

• ) technique for the synthesis of dialkyl carbonates [90]. Using potassium carbonate, alkyl halide and 2 equiv of phase-transfer catalyst 18-crown-6 yielded dialkyl carbonate in 74%. However, in absence of 18-crown-6 the yield was only 2% at 17 h (Scheme 20). Transesterification is a synthetic approach mostly

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• azodicarboxylates 38 [147]. Addition of a nucleophile like β-ketoesters 1 to 38 gives the corresponding hydrazides 39, which can then be further manipulated with established methods [137][142][143]. In 2008, Maruoka’s group reported the use of the chiral phosphonium salt F2 as a phase-transfer catalyst for the α

• performed even slightly more selective with low catalyst loadings of 1 mol % only [143]. As discussed before already, the spirocyclic phosphonium salt F1 was recently used as a phase-transfer catalyst for asymmetric α-fluorination reactions by the groups of Cahard and Ma (Scheme 3) [80]. The same groups

Mechanochemical N-alkylation of imides

• Anamarija Briš,
• Mateja Đud and
• Davor Margetić

Beilstein J. Org. Chem. 2017, 13, 1745–1752, doi:10.3762/bjoc.13.169

• need for tetrabutylammonium iodide as phase-transfer catalyst to increase the limited solubility of 14. The selectivity was observed for certain substrates. For example, the alkylation of phthalimide 12 with 1,4-bis(bromomethyl)benzene led to the formation of two products, namely 28 and 29. By keeping

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• variety of aryl halides were converted to the corresponding phenols. Fu and co-workers employed pyridine-2-aldoxime (PAO, L7) as ligand and developed a Cu2O catalyzed hydroxylation protocol [33]. The reaction was carried out at 110 °C in water in the presence of n-Bu4NBr as phase transfer catalyst (Scheme

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

• Faith M. Akwi and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 1987–2004, doi:10.3762/bjoc.12.186

• transfer synthesis’ in micro-chips for a diazo-coupling reaction [23]. The authors did not however employ a phase transfer catalyst, but rather the principle to increase the reaction selectivity in the diazo coupling of 5-methylresorcinol (10) to p-nitrobenzene diazonium tetrafloroborate (11) in a biphasic

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• HCPN-59 can be used in an asymmetric cyclopropanation. The hydrocupreine and hydrocupreidine-based catalysts HCPN-65 and HCPD-67 demonstrate the potential for phase transfer catalyst derivatives of the 6’-OH cinchona alkaloids to be used in asymmetric synthesis. Jørgensen’s oxaziridination. Zhou’s α

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• . According to the obtained results, the presence of KB(C6F5)4 as the phase-transfer catalyst could accelerate the reaction rate and enhance the yield of the products. On the other hand, the KI could promote the formation of the active cuprate species (BPMED)CuI2−, thus allowing less reactive substrates to

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• -transfer catalyst such as tetrabutylammonium iodide generated bicyclic compounds 341a–c. The RRM of these ether derivatives 341a–c was performed under ethylene (24) atmosphere with catalyst 5 to generate the dihydrofuran derivatives 342a–c. When compounds 340d, 340e and 340f were subjected to a metathesis

• RRM approach. In this regard, secondary alcohol derivatives related to 8-oxabicyclo[3.2.1]octenes such as 341a,b,c were used as potential precursors for the synthesis of a variety of cyclic polyethers [71]. Allylation of 340a–c using sodium hydride and allyl bromide (37) in the presence of a phase

Design and synthesis of polycyclic sulfones via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1373–1378, doi:10.3762/bjoc.11.148

• methanesulfonyl chloride in the presence of triethylamine as a base to obtain the dimesylate 3 (89%). Next, compound 3 was subjected to a cyclization reaction by treating with sodium sulfide nonahydrate (Na2S·9H2O) using 20% Aliquat® 336 as a phase–transfer catalyst (PTC) to produce the known sulfide 5 (83%) [31

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

• Malgorzata Adamkiewicz,
• David O’Hagan and
• Georg Hähner

Beilstein J. Org. Chem. 2014, 10, 2897–2902, doi:10.3762/bjoc.10.307

• time required to be optimised. The reaction temperature was kept at 25 °C and the phase-transfer catalyst, benzyltriethylammonium chloride (BTEAC) was chosen to generate the :CX2 carbenes, and minimise exposure of the wafers to the base. The Ruppert–Prakash reagent (TMSCF3) was used to prepare the gem

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• from a concurrent elimination as well as a rearrangement reaction. In superoxide chemistry many aprotic solvents have been used. We prefer DMSO because the solubility of potassium superoxide is better in DMSO compared to other solvents [16]. As the phase-transfer catalyst can enhance the extent of

Expeditive synthesis of trithiotriazine-cored glycoclusters and inhibition of Pseudomonas aeruginosa biofilm formation

• Meriem Smadhi,
• Sophie de Bentzmann,
• Anne Imberty,
• Marc Gingras,
• Raoudha Abderrahim and
• Peter G. Goekjian

Beilstein J. Org. Chem. 2014, 10, 1981–1990, doi:10.3762/bjoc.10.206

• dimethyldioxirane (DMDO) generated in situ in the presence of a phase-transfer catalyst, followed by treatment with NaN3 [39]. This afforded the silyl-protected D-galactose trithiotriazine–triazole glycocluster 11 under CuSO4/sodium ascorbate-catalyzed cycloaddition conditions [40] (20 °C, 24 h), in a satisfactory

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• glycol in the presence of tetrabutylammonium hydrogen sulfate as both an acid and a phase-transfer catalyst (Scheme 28) [100]. As the authors suggested, the formation of intermediate N-acyliminium ion from aldehyde 75 and (thio)urea was the key step of the reaction. Protonation of aldehyde 75 by

• reactions were carried out in the presence of tetrabutylammonium hydrogen sulfate as a phase-transfer catalyst. The yield of products 93 varied from 90% to 98%. As the authors suggested on the basis of comparative experiments performed without the catalyst, tetrabutylammonium hydrogen sulfate facilitated

Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ₀)

• Sabin Llona-Minguez and
• Simon P. Mackay

Beilstein J. Org. Chem. 2014, 10, 1333–1338, doi:10.3762/bjoc.10.135

• ] (Figure 3). The resulting pivalamide 8 proved to be more soluble than 1 and the subsequent halogenation step was accomplished in the presence of a phase transfer catalyst, affording the desired chloro-intermediate 9 in fair yield. In our hands, nucleophilic aromatic substitution on 9 using amines of

C–C Bond formation catalyzed by natural gelatin and collagen proteins

• Dennis Kühbeck,
• Basab Bijayi Dhar,
• Eva-Maria Schön,
• Carlos Cativiela,
• Vicente Gotor-Fernández and
• David Díaz Díaz

Beilstein J. Org. Chem. 2013, 9, 1111–1118, doi:10.3762/bjoc.9.123

• the phase-transfer catalyst also suggests potential relevance to physiological conditions, where biological membranes can be expected to serve a similar role. The background reaction in DMSO (i.e., control experiment in the absence of protein) was totally inhibited, and in H2O/TBAB represented only 10

• was used as the solvent system the reduction of the catalytic activity was less dramatic than in the case of DMSO. However, such apparently better performance in water/TBAB was dependent on the addition of extra TBAB after each cycle in order to ensure a constant concentration of the phase-transfer

• catalyst during the reaction. The continuing loss of TBAB during the work-up after each cycle was quantified by 1H NMR analysis of the reaction crude. Very interestingly, we found that the direct use of the precursor collagen as biocatalyst also afforded the desired product in very good yields. In this