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

• strand interactions were observed in a DNA–DNA duplex [43]. TIPDS protection of uridine (16), followed by the treatment of the product with acetic anhydride/acetic acid in DMSO produced the protected nucleoside 17 [45][46] (Scheme 5). Next, the fully protected nucleoside 17 was subjected to chlorination

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• unexpected. The mechanism of the formation of 4 is not easy to clarify, and presently, there is no indication of whether the reaction proceeds via a homolytic or heterolytic process. Notably, similar unexpected chlorination reactions have been described in the past [56][57]. While the metallated form of the

Manganese/bipyridine-catalyzed non-directed C(sp³)–H bromination using NBS and TMSN₃

• Kumar Sneh,
• Takeru Torigoe and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2021, 17, 885–890, doi:10.3762/bjoc.17.74

• reported the manganese-porphyrin-catalyzed chlorination and bromination of C(sp3)−H bonds, respectively (Scheme 1d). Groves et al. also reported the manganese-salen-catalyzed fluorination of benzylic C(sp3)−H bonds [49]. Although these methods are efficient, they have a limited substrate scope

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• )chloromethane via a published protocol for radical chlorination of an acetal due to the presence of vulnerable benzylic methyl groups proximate to the acetal [10]. We then synthesized carboxylic acid 9, from which we anticipated creating an aryloxylchlorofluoromethane (10, X = Cl, Scheme 4) via

Metal-free visible-light-enabled vicinal trifluoromethyl dithiolation of unactivated alkenes

• Xiaojuan Li,
• Qiang Zhang,
• Weigang Zhang,
• Jinzhu Ma,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2021, 17, 551–557, doi:10.3762/bjoc.17.49

• approaches for the trifluoromethylthio (SCF3) difunctionalization of alkenes, such as cyanation [23], etherification [24][25][26][27], amination [28][29][30], chlorination [31][32], hydrogenation [33], trifluoromethylation [34], phosphonization [35], arylation [36][37][38], trifluoromethylthiolation [39

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• ) were modest inhibitors. The synthesis started from diphenyl N-Cbz-1-aminoalkylphosphonates 11 (Scheme 1). They were transformed to dimethyl esters via transesterification and further to monomethyl esters 12 via basic hydrolysis. After chlorination with thionyl chloride, the monomethyl esters 12 were

• tryptophan amide with 4-nitrobenzyl (R)-N-Fmoc 1-amino(cyclohexyl)methylphosphonochloridate (38), which was prepared from diethyl (R)-N-Fmoc 1-amino(cyclohexyl)methylphosphonate (36) via a selective basic hydrolysis, chlorination, esterification with 4-nitrobenzyl alcohol, selective basic hydrolysis, and

• chlorination. After the treatment of compound 39 with piperidine, the N-terminal free dipeptide was obtained and acylated with hexanedioic anhydride to afford the designed hapten 40 (Scheme 7) [11]. Phosphonodepsioctapeptide 41 was prepared as a variation of the partial sequence of a gene product of erb B-2

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• ], with FeCl3 being particularly notable for its versatility, ease of use, and low price [5]. Nevertheless, the synthetic utility of oxidative couplings is often limited by several factors [6]. Consequently, incomplete ring fusion and various side reactions, e.g., chlorination [7], or unexpected

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• originally reported by Sommerwerk [16] (Scheme 1). In this case, 18β-glycyrrhetinic acid reacted with acetic anhydride in the presence of triethylamine to give 3-acetyl-18β-glycyrrhetinic acid (2), which by successive chlorination with oxalyl chloride yielded acyl chloride 3. Without isolation, the

• intermediate 3 reacted with piperazine to give 18β-glycyrrhetinic acid piperazinyl amide 4. The total yield of chlorination and amidation reactions was 67%. In the beginning, the reaction of acyl chloride 3 with piperazine was taken as a prototypical case to ascertain and screen the experimental conditions

Synthesis of disparlure and monachalure enantiomers from 2,3-butanediacetals

• Adam Drop,
• Hubert Wojtasek and
• Bożena Frąckowiak-Wojtasek

Beilstein J. Org. Chem. 2020, 16, 616–620, doi:10.3762/bjoc.16.57

• enantioselective reactions, such as the Sharpless epoxidation [19][20][21][22][23][24], asymmetric dihydroxylation [25][26], chloroallyloboronation [27], or iodolactonization [28]. Most recently a method using the asymmetric chlorination of dodecanal by LiCl in the presence of a chiral imidazolidinone catalyst has

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• quinazolinones 89. Subsequent chlorination of the quinazolinone resulted in the formation of 4-chloroquinazoline intermediates 90. The subsequent Pd-catalyzed coupling of 90 and arylboronic acid 91 gave the methoxy intermediates 92 in reasonable yields. The demethylation of the 2-(2-pyridyl)methoxy intermediate

• was obtained by the reaction of ʟ-valinol with in situ-generated indolylacyl chloride. The latter compound was obtained through an oxalic acid-mediated chlorination of carboxylic acid 96 with dimethylformamide as catalyst in dichloromethane. Next, oxazoline derivative 98 was obtained via a

• carbon dioxide and phenyllithium gives the phosphine ferrocene carboxylic acid 152 as the major reagent. Oxidation of the phosphine using hydrogen peroxide generated the phosphine oxide 153. In situ chlorination of the carboxylic acid followed by addition of the chiral amino alcohols gave the phosphoryl

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• coupling is followed by chlorination, this protocol exploits the improved deprotonation efficiency of 2 toward 3’-unsubstituted 3-substituted bithiophene, and this method enabled the synthesis of 4 (where R1 = H) regioselectively. Polymerization of 4 (where R1 = n-hexyl and R2 = (CH2)4Si(Me2)OSiMe3) was

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• prepared a library of monobrominated compounds using this simple yet effective strategy. A plausible mechanism is shown in Figure 21. Chlorination of arenes with Mes-Acr-MeClO4 (2): Ohkubo et al. observed that only under aerobic photocatalytic conditions, C–H chlorination of trimethoxybenzene (TMB) occurs

• in situ, followed by ipso-chlorination, which yielded the desired products with high regioselectivity. The substrate scope is displayed in Scheme 23, and the mechanism involved in this transformation is shown in Figure 23. Monofluorination of arenes: Direct monofluorination has always been a

• of substituted phenols using QuCN. Synthesis of substituted phenols with DDQ (5). Aerobic bromination of arenes using an acridinium-based photocatalyst. Aerobic bromination of arenes with anthraquinone. Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2). Chlorination of arenes with 4CzIPN

An improved, scalable synthesis of Notum inhibitor LP-922056 using 1-chloro-1,2-benziodoxol-3-one as a superior electrophilic chlorinating agent

• Nicky J. Willis,
• Elliott D. Bayle,
• George Papageorgiou,
• David Steadman,
• Benjamin N. Atkinson,
• William Mahy and
• Paul V. Fish

Beilstein J. Org. Chem. 2019, 15, 2790–2797, doi:10.3762/bjoc.15.271

• -boronate 11 (5 → 6), and (2) C6 chlorination was performed with 1-chloro-1,2-benziodoxol-3-one (12) (6 → 7) as a mild and selective electrophilic chlorination agent. This 7-step route from 16 has been reliably performed on large scale to produce multigram quantities of 1 in good efficiency and high purity

• 1 (or 17) which combines Notum inhibition with CNS penetration would be a valuable chemical probe for investigating the role of Notum in disease models. Keywords: brain penetration; 1-chloro-1,2-benziodoxol-3-one; electrophilic chlorination; LP-922056; Notum inhibitor; Introduction The Wnt

• group was most effectively achieved with a Suzuki–Miyaura cross-coupling reaction with MIDA-boronate 11 (5 → 6); and (2) C6 chlorination was performed with 1-chloro-1,2-benziodoxol-3-one (12) (6 → 7) as a mild selective electrophilic chlorination agent. 4-Chlorothieno[3,2-d]pyrimidine (3) was either

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• (Table 2). In both series, di-ortho-chlorination is predicted to provide the higher overlap in π–π* bands between Z and E, for which a less efficient E-to-Z photoconversion is therefore expected. In addition to the band separation, the n–π* transition is required to be relatively intense for the Z-isomer

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• ]. Norfloxacin (1) is considered to be the first broad band antibiotic and its structurally related cousin ciprofloxacin (2) is one of the most prescribed antibiotics even after 20 years of clinical use. We elected 1 as a synthetic target for our novel approach towards FQs (Scheme 4). Chlorination of

Metal-free mechanochemical oxidations in Ertalyte^® jars

• Andrea Porcheddu,
• Francesco Delogu,
• Lidia De Luca,
• Claudia Fattuoni and
• Evelina Colacino

Beilstein J. Org. Chem. 2019, 15, 1786–1794, doi:10.3762/bjoc.15.172

• , entries 7 and 8) other than NaHCO3 significantly reduces the alcohol-to-aldehyde conversions. Based on these preliminary results, we decided to replace aqueous NaOCl (bleach) with Ca(OCl)2 that has been reported previously as a valid alternative to NaOCl aqueous solutions for mechanochemical chlorination

• furfural (10b), but in low and irreproducible yields together with significant amounts of byproducts. As expected, the reaction with conjugated alcohols (cinnamic alcohol, propargyl alcohol, etc.) was less successful due to the competing chlorination of the multiple bonds. Prompted by these findings, we

Introduction of an isoxazoline unit to the β-position of porphyrin via regioselective 1,3-dipolar cycloaddition reaction

• Xiujun Liu,
• Xiang Ma and
• Yaqing Feng

Beilstein J. Org. Chem. 2019, 15, 1434–1440, doi:10.3762/bjoc.15.143

• Vilsmeier reaction was carried out after insertion of Cu2+ into the cavity of TPP. In the presence of concentrated H2SO4 the Cu2+ was removed to give the 2-formyl derivative TPP-CHO. Subsequently, the formyl group was reduced by NaBH4, accompanied with chlorination by SOCl2, to afford the chloromethyl

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• studied this reaction and found that the phosphorylation step should be conducted under strictly controlled temperature conditions in the range of −5 to 0 °C to prevent the undesired 5′-chlorination which occurs at higher temperatures, and to avoid slow reaction rates at lower temperatures. Lee et al. [27

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• ring-opening and chlorination of cyclopropanols with aldehydes. Ag(I)-catalyzed ring-opening/alkynylation of cyclopropanols with EBX. Na2S2O8-promoted ring-opening/alkylation of cyclopropanols with acrylamides. Cyclopropanol ring-opening initiated tandem cyclization with acrylamides or 2

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• (12) in 94% yield using triphosgene, a standard reagent for the chlorination of phosphorus–hydrogen bonds [49]. Since a direct reaction with an excess of the Grignard reagent BrMg(CH2)6CH=CH2 would give 11, a dead end, initial conversion to the bis(borane) adduct 12·2BH3 was envisioned. However

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

• (Figure 2). Using a 5-stage variant, various unsymmetrical N-chloramines were produced with unprecedented productivities (Table 1). The rapid nature of this chlorination step makes in situ generation and consumption feasible in flow mode. Comparing Table 1, entries 1 and 3, the 5-stage CSTR, with one

• may be more of a problem in batch with the longer reaction time [48]. Conclusion A continuous-flow approach to prepare and handle unstable N-chloramines is reported. The method exploits the superior mixing of a CSTR compared with classical batch, to enable fast N-chlorination of amines under biphasic

Phosphoramidite building blocks with protected nitroxides for the synthesis of spin-labeled DNA and RNA

• Timo Weinrich,
• Eva A. Jaumann,
• Ute M. Scheffer,
• Thomas F. Prisner and
• Michael W. Göbel

Beilstein J. Org. Chem. 2018, 14, 1563–1569, doi:10.3762/bjoc.14.133

• 6-chloro derivative 13 as starting material, easily accessible from deoxyadenosine via enzymatic deamination, acetylation [37] and chlorination. This compound reacted cleanly and yielded 67% of the TEMPO conjugate 14. After deacetylation (15) and tritylation (16), amidite building block 7 was

• similar way as 13 by enzymatic deamination of adenosine, acetylation [46] and chlorination. A clean reaction with amino-TEMPO compound 10 then produced 78% of compound 18. Ester hydrolysis (19) and tritylation afforded 20 which was silylated with 1.8 equiv of TBS chloride. Although the 3’-silylated and

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• acetonitrile [31]. Moreover, we investigated the reaction of 1a with SO2Cl2. Here, two reaction products – 8 and 9 – were isolated, whereas in both cases chlorination not only at the pyrazole C4 but also in the 4-position of the phenyl ring took place (Scheme 5). The reaction mechanism for the transformation 1

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• -benzosuberone 246 with Ac2O/AcOH/HCl (Scheme 39) [161]. The olefin 249, derived from reduction, chlorination, and elimination of 247, was converted by SeO2 in refluxing dioxane or xylene to the acetamido-benzotropone 250, which in turn can be hydrolyzed to 2-hydroxy-4,5-benzotropone (238). 5.1.2. Reactions of 2