An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks

• Sushil K. Maurya and
• Rohit Rana

Beilstein J. Org. Chem. 2017, 13, 1106–1118, doi:10.3762/bjoc.13.110

• blocks were coupled via 1,3-dipolar cycloaddition (click reaction) iteratively through the development of a greener base-free Cu(I)-catalyzed azide–alkyne cycloaddition reaction. The cycloadducts were then converted to macrocycles by Ru-catalyzed cyclization reaction using greener and non-hazards

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• , phenylsilane and butylene oxide [23][24], and reactions with the combination of achiral 30, trimethoxysilane ((MeO)3SiH) and sodium carbonate using conventional heating [25]. Additionally, the same authors have reported base-free Wittig reactions using diethyl maleate (31) as the starting material to form

• -workers appeared, Wenwei Lin and a co-worker published conceptually similar catalytic Wittig reactions that were based on their previous research regarding related non-catalytic phosphine-mediated base-free Wittig reactions (Scheme 10) [28]. They started with Michael acceptors 36 to generate products 37

• -supported telluride catalyst cycling. Stable and odourless telluronium salt pre-catalyst for Wittig-type reactions. Phosphine-catalyzed Wittig reactions. Enantioselective catalytic Wittig reaction reported by Werner. Base-free catalytic Wittig reactions reported by Werner. Catalytic Wittig reactions

Scope and limitations of a DMF bio-alternative within Sonogashira cross-coupling and Cacchi-type annulation

• Kirsty L. Wilson,
• Alan R. Kennedy,
• Jane Murray,
• Ben Greatrex,
• Craig Jamieson and
• Allan J. B. Watson

Beilstein J. Org. Chem. 2016, 12, 2005–2011, doi:10.3762/bjoc.12.187

• necessitate base-free or exceptionally mildly basic reaction conditions. In contrast, amide-bond formation is the most practiced reaction in the pharmaceutical industry [4] and these are routinely performed in DMF at room temperature in the presence of organic bases [53]. As such, Cyrene may offer

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• -bromo-1,1-dimethylindene. Keywords: base-free dehydrobromination; cis/trans stereochemistry; five-membered ring conformation; indenes; NMR couplings; Introduction The basic mechanistic features of competing suprafacial and antarafacial additions of elemental bromine to an olefin are reasonably well

• observed value of 8.4 Hz that is explained by the predominant 2ax-H,3ax-H conformation. Distillation of the trans/cis product mixture led to some enrichment of the thermally more stable diastereomer trans-1 due to the “base-free” HBr elimination from cis-1 with formation of 2-bromo-1,1-dimethylindene (4 in

• KOH in EtOH) to produce the monobromides 3 and 4. It may be noticed that 4 (from cis-1) cannot have been an intermediate in the initial step of the above “base-free” conversion of 9 to 7, since 4 would generate the thermally stable tribromide 6 that was not detected in the initial product mixture of 1

Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

• Bin Yin,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2015, 11, 85–91, doi:10.3762/bjoc.11.12

• cationic intermediate D. In the cases of 1b and 1d having electron-withdrawing ester and acetyl groups, the α-protons are acidic enough and can be cleaved by either base, free Et3N (from Et3N·3HF) [37] or fluoride ions (from Et4NF·3HF). The resulting cation E reacts with a fluoride ion to form 2b and 2d

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• calculations for the first time. B3LYP/6-311+G(d,p) SCRF=(PCM, solvent = 1,2-ethanediol) optimizations were carried out. To investigate the role of the base catalyst, the base-free reaction was examined by the use of acetone, hydrazine (H2N–NH2) and (H2O)8. A ready reaction channel of acetone → acetone

• hydrazine (Me2C=N–NH2) was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N2 extrusion step from the isopropyl diimine intermediate (Me2C(H)–N=N–H). Two base-catalyzed reactions were investigated by models of the ketone

• is this base-free reaction remarkably efficient and of high yield even under mild and simple conditions (Scheme 3). In fact, the neutral condensation was confirmed as probable by DFT calculations of a reaction system composed of Ph–CHO, H2C(CN)2 and (H2O)12 [15]. In spite of its fundamental character

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• (Table 24) [94]. A similar approach has been reported by K.-W. Huang and Z. Weng employing organotrifluoroborates under base free conditions (Table 25) [95]. 3.2.7 Radical trifluoromethylation of arylboron reagents. In contrast to previous approaches where relatively expensive trifluoromethylsilanes are

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• different reaction conditions employing base-free, ligand-free conditions or by using conventional oxidants such as oxygen, benzoquinone, Cu salts, etc. [48][49][50][51][52][53]. In this article we report two new protocols for Heck cross-coupling reactions: (i) a stable SPO ligated palladium complex 6

• -unsaturated esters 3o–3q were obtained in 90–95% yields, respectively. Heck reaction of arylboronic acids with olefins The phosphine- and base-free coupling of arylboronic acids with olefins under mild reaction conditions were studied as well to broaden the scope of cross-coupling reactions. To search for the

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• formate (HCO2−) does. H2 transfer from formic acid to a nitro compound has often been facilitated in the presence of a base, such as triethylamine and NH3 [28][32][42][43][44]. Therefore, the addition of such bases is usually necessary for transfer hydrogenation. As in the present case, base-free

Intramolecular carbonickelation of alkenes

• Rudy Lhermet,
• Muriel Durandetti and
• Jacques Maddaluno

Beilstein J. Org. Chem. 2013, 9, 710–716, doi:10.3762/bjoc.9.81

• this heterocyclization reaction to various nonactivated olefins in a nickel-catalyzed intramolecular base-free Heck-type coupling. Results and Discussion Scope of the reaction We applied the Nickel-catalyzed intramolecular base-free Heck-type coupling to two model substrates, assumed to provide either

• the expected (and sole) tricyclic product 14 in 52% isolated yield, resulting from a nickel-catalyzed intramolecular base-free Heck-type coupling and exhibiting an all-carbon quaternary center at a cis-ring junction (as established by NOESY experiments). This result, added to that obtained above with

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• of inexpensive potassium thioacetate with both electron-rich and electron-poor aryl iodides under a base-free copper/ligand catalytic system. CuI as copper source affords S-aryl thioacetates in good to excellent yields, by using 1,10-phenanthroline as a ligand in toluene at 100 °C after 24 h. Under

• the reactions of KSCOMe (1) with aryl iodides under a Cu/ligand/base-free system to afford S-aryl thioacetates 2 as thiol surrogates in good to excellent yields, under conventional heating and microwave irradiation as an efficient access to a variety of sulfur compounds. Results and Discussion

• . Electron-donor and electron-acceptor substituents are tolerated, and polysubstitution can also be successfully accomplished. Experimental Representative experimental procedures for the Cu-catalyzed base-free C–S coupling Method A: The reactions were carried out in a 10 mL two-necked Schlenk tube, equipped

Caryolene-forming carbocation rearrangements

• Quynh Nhu N. Nguyen and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2013, 9, 323–331, doi:10.3762/bjoc.9.37

• , several interesting structures with unusual bonding arrays are encountered along the base-free pathway. Experimental All calculations were carried out with Gaussian 09 [65]. Geometry optimizations, frequency calculations and intrinsic reaction coordinate (IRC) [66][67] calculations were first carried out

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• with aryliodides under base-free and ligandless conditions in DMF as solvent [42][43]. However under the developed conditions, the direct coupling of oxazole proved to be inefficient (Scheme 7). More recently, Piguel disclosed an original, ligandless, microwave-assisted, Pd(0)/Cu(I)-catalyzed protocol

Synthesis of (−)-julocrotine and a diversity oriented Ugi-approach to analogues and probes

• Ricardo A. W. Neves Filho,
• Bernhard Westermann and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2011, 7, 1504–1507, doi:10.3762/bjoc.7.175

• chiral center of 4 can be observed even in the presence of weak bases such as potassium carbonate [17]. Thus, we decided to use a base-free N-alkylation protocol, namely the Mitsunobu reaction of 3 and the readily available 2-phenylethanol [18]. This protocol gave the desired optically active product in

Chemoselective reduction of aldehydes by ruthenium trichloride and resin- bound formates

• Basudeb Basu,
• Bablee Mandal,
• Sajal Das,
• Pralay Das and
• Ashis K. Nanda

Beilstein J. Org. Chem. 2008, 4, No. 53, doi:10.3762/bjoc.4.53

• . The reaction conditions appear to be mild and base-free, and give high yields of the corresponding alcohols and free of any by-product. Of interest is that, although the use of base co-catalysts for metal complex catalyzed hydrogen transfer is common [27][28][29][30], the present reaction conditions

• of aryl aldehydes and 1,2-diketones to aryl alcohols and α-hydroxy ketones respectively under mild, base-free and phosphine- or any ligand-free conditions. It is observed that aryl ketones and several other potentially reducible functionalities remain unchanged under the reaction conditions. The

N-Arylation of amines, amides, imides and sulfonamides with arylboroxines catalyzed by simple copper salt/EtOH system

• Zhang-Guo Zheng,
• Jun Wen,
• Na Wang,
• Bo Wu and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2008, 4, No. 40, doi:10.3762/bjoc.4.40

• with arylboroxine catalyzed by simple copper salt in EtOH was developed in this paper. The catalytic system is base-free, economical, easy to handle and does not need addition of oxygen. Different reaction conditions such as copper salt, temperature, solvent were systematically optimized. The N