Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• 35 which upon further reaction with silylated uracil in the presence of tin(IV) chloride via Vorbrüggen coupling afforded the protected double-headed nucleoside 36. The nucleoside 36 was finally deprotected in the presence of Pd(OH)2/C under hydrogen atmosphere to generate the double-headed

• ′-thymin-1-yl derivatives of 2′-deoxythymidine, i.e., compounds 59 and 60 starting from 5′-O-tritylthymidine (55). The tritylated thymidine 55 first was converted to the protected azide derivative 57 in two steps, followed by its reduction in the presence of tin(II) chloride, thiophenol and triethylamine

• , followed by reduction of the corresponding nucleoside with tin chloride produced nucleoside 62 which was treated as a key intermediate for the production of the double-headed nucleosides 63 and 64. Reaction of nucleoside 62 with 3-ethoxypropenoyl isocyanate or 3-methoxy-2-methylpropenoyl isocyanate in a

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• DDQ and the subsequent abstraction of hydride from the benzylic or allylic position generated a charge-transfer complex 298. The complex 298 formed a tin-containing ate oxocarbenium ion complex 299 with SnBr4, and then rapid C–C bond formation took place to generate the cyclic intermediate 300. The

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• by 5'-tritylation. In the case of guanosine, this strategy for 2'-OH methylation was unsuccessful, owing again to undesired methylation at the nucleobase. Instead, the 5'-O-monomethoxytrityl derivative of N2-isobutyrylguanosine was treated with diazomethane in dimethylformamide in the presence of tin

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• drawback because organomercury compounds are extremely toxic and environmentally persistent. Decomposition of trimethyl(trifluoromethyl)tin in the presence of sodium iodide: It is also possible to prepare difluorocyclopropanes from olefins and trifluoromethyl derivatives of tin such as trimethyl

• (trifluoromethyl)tin (48). There are two possible ways to obtain difluorocarbene from 48: thermal (at 140–150 °C, 20–44 h) [59] and iodide ion induced (at 85 °C, 16 h) (Scheme 19) [60]. The trapping with alkenes gave the expected cyclopropanes. The reaction of (СН3)3SnСF3 (48) with NaI (1 equiv) occurred in 1,2

• alcohols, ethers, esters, and amines (121, Scheme 53) [103]. They proposed that an initial tin–lithium exchange was followed by a β-elimination of LiF to form the intermediate cyclopropenes 119. The ring opening of the latter then generated the vinylcarbenes 120. The carbenes 120 could then insert into the

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• formal synthesis of inthomycin C ((−)-3). In 2018, Donohoe et al. demonstrated a tin-free, short and efficient total synthesis of inthomycin C ((−)-3) by comprising the three key steps of C−C bond-forming reactions: i) a vinylogous Mukaiyama aldol reaction, ii) an olefin cross-metathesis reaction, and

• Hale and Hatakeyama [57]. Recently, Burton’s group developed some efficient and tin-free total syntheses of all three inthomycins A–C ((+)-1, (+)-2, and (−)-3) using a Suzuki or Sonogashira cross-coupling of the (E)- or (Z)-alkenyl iodides 130 with the dienylboronic ester 128 as key step (Schemes 18–22

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• .2.1] carbocyclic skeletons, which is applied to the synthesis of phyllocladanol (21) [68] (Scheme 12A). The IMCC precursor 147 was prepared from aldehyde 146 in nine steps. The IMCC precursor 147 underwent an intramolecular cross-cycloaddition catalyzed by tin tetrachloride to give tetracycle 149 in

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• occurred as demonstrated by Havinga more than 70 years ago [69]. In alternative, the irradiation of monoaryl phosphates in the presence of a strong nucleophile (e.g., a tin anion) led to an ipso substitution reaction via an ArSRN1 process [70]. The situation dramatically changes when a further aryl group

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• brominated tin porphyrin (SnTBPP) as monomer (Scheme 47). The irradiation of this material in the presence of both sulfides and molecular oxygen furnished a variety of sulfoxides in 70–97% yields. The SnPor@PAF presented the same photocatalytic activity of its monomer (SnTBPP) with the advantage of its easy

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• to industrial production [20][21][22][23][24][25]. Very recently, tin(II) 2-ethylhexanoate has been reported as an efficient catalyst for the synthesis of oligomeric ricinoleic acid [19]. Unfortunately, the separation of oligomeric ricinoleic acid and the recovery of the catalyst still encounters

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• organometallic species of Cd [16], Ga [17], In [18], Ti [19], Al [20] and Bi [21] were described. However, the majority of these methods involve reagents that are difficult to prepare and to handle due to the sensitivity to air and moisture. The use of less reactive species based on tin [22][23][24], silicon [25

• interesting to note that the nitro group remained intact under the reaction conditions. Usually, this group is sensitive to reduction when alternative methods involving zinc or tin are used [33]. In addition, aldehydes containing halogens also gave the corresponding products 2j–l in moderate yields. These

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• competing Lewis basic sites in 4 and 5. The use of tin(IV) chloride (stannic chloride) provided generally a slightly faster reaction but with slightly lower yields, except in the case of the 5/allyltrimethylsilane/7a combination (Table 1, entry 5). Reactions were more successful when the amount of

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• in the presence of acetic anhydride. Among the various Lewis acids tested, the desired acetolysis products were obtained in moderate yields under tin(IV) chloride catalysis. Our methodology could be extended to regioselective protecting group installations and manipulations towards a number of

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• the elongated unit at the reducing end of the disaccharide. Keywords: carbohydrates; C–C bond formation; indium-mediated allylation; melibiose; ozonolysis; Introduction The tin and indium-mediated allylation (IMA) proved to be useful synthetic tools for the chain elongation of unprotected

• reported for the first time a tin-mediated allylation of unprotected carbohydrates followed by ozonolysis allowing for easy accessibility of the corresponding elongated sugars [2]. In the same year, Chan and Li introduced indium for the allylation of aldehydes and furthermore demonstrated the applicability

• concerning their effects on the conversion rate as well as the diastereoselectivity (Table 1). Concerning the metal species, it is known that indium provides several advantages compared to other allylation-mediating metals such as tin, as it allows the reaction to proceed under very mild conditions without

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• (Figure 2) [26][27]. In addition, 1-acyl-5-hydroxypyrazolines are bidentate ligands for zinc complexes and by virtue of being ring tautomers of β-enolhydrazones they can also act as tridentate ligands for nickel [28] and tin [29][30] complexes. In contrast, dimethylzinc forms dimeric complexes where the 1

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• photochromic derivatives with varying electronic and thus photochromic properties. The respective arylamines 13a–c were converted into their corresponding hydrazines 14a–c via diazonium-salt formation using sodium nitrite and subsequent reduction using tin(II) chloride [70]. The following nucleophilic

Regioselective addition of Grignard reagents to N-acylpyrazinium salts: synthesis of substituted 1,2-dihydropyrazines and Δ⁵-2-oxopiperazines

• Valentine R. St. Hilaire,
• William E. Hopkins,
• Yenteeo S. Miller,
• Srinivasa R. Dandepally and
• Alfred L. Williams

Beilstein J. Org. Chem. 2019, 15, 72–78, doi:10.3762/bjoc.15.8

• , Table 1). Changing the solvent to diethyl ether showed no improvement in the yield of 3a but when THF was used, an excellent yield of 87% was produced (entries 4 and 5, Table 1). Based on our previously developed selective tin hydride reduction of monosubstituted pyrazinium salts [9], we expected the

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• corresponding alkynyl alcohols requires the handling of toxic tin reagents [8][9]. During these last years, ring-closing metathesis (RCM) of vinyl ethers have proved to be an efficient method for the preparation of chiral glycal scaffolds [11][12][13][14][15][16][17][18] as demonstrated in some total syntheses

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• obtained through isomerization with 1,2-migration of the ester groups. The B12-TiO2 hybrid catalyst can be regarded as a good alternative for conventional radical-involved organic syntheses using tin compounds. Recently, we discovered that the B12 derivative 1 can mediate trifluoromethylation and

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• -decorated TTF-rotaxanes was achieved by Gao and co-workers [95]. They deposited a thin-film of bistable donor–acceptor rotaxanes on an indium tin oxide (ITO)-coated substrate. A clean electrochemical switching on the substrate was observed with current–voltage curves showing a clear memory effect. The

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• = 10 kV). Xerogels, prepared by freeze-drying the corresponding gels, were placed on top of a tin plate and shielded with Pt (40 mA, 30–60 s; film thickness = 5–10 nm). Images were obtained by Servicio General de Apoyo a la Investigación-SAI (Universidad de Zaragoza). Chemical structures of isosteric

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• diastereomers (>90% de) in both uniformly excellent yields (90–98%) and enantioselectivities (94–99% ee). In only one case of substrate (Ar = 1-Naph), a lower yield (78%) albeit combined with a comparable very good enantioselectivity (93% ee) was obtained. The same year, (S)-BINOL-derived tin dibromide 30 was

• lowest yield (31%). The authors have proposed that the true catalyst of the reaction was a chiral tin iodide methoxide 34 in situ generated from chiral tin bromide 30, two equivalents of NaI and NaOMe (Scheme 10). Enantioselective aza-Morita–Baylis–Hillman reactions The Morita–Baylis–Hillman reaction is

• -isatin imines with silyl ketene imines. Tin-catalyzed Mannich reaction of N-arylisatin imines with an alkenyl trichloroacetate. Aza-Morita–Baylis–Hillman reaction of N-Boc-isatin imines with acrolein catalyzed by β-isocupreidine. Aza-Morita–Baylis–Hillman reaction of N-Boc-isatin imines with acrolein (35

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• for catalysts rich in tin. Suzuki–Miyaura coupling reactions Batch reactions The catalytic activity of the synthesised catalysts in the Suzuki–Miyaura reaction was investigated using phenylboronic acid 3 in combination with various bromoarenes 4a–e, featuring ortho- and para-substitution of electron

• monitored by high-performance liquid chromatography (HPLC). In general, the catalysts with tin proportions of 0.20, 0.79 and 0.99 proved to be most effective in the desired transformations with exceptional high activities (turn over frequency, TOF > 12,000 h−1) in all tested Suzuki–Miyaura cross-coupling

• termination of the transformation just at the moment of full conversion. In conclusion, Ce0.99−xSnxPd0.01O2−δ (x = 0–0.99) proved to be very active catalysts for Suzuki–Miyaura reactions. Based on the experimental results, the tin and cerium content of the catalysts respectively do not seem to be directly