Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris

• Angelique Ladwig,
• Markus Kroll and
• Stefan Schulz

Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16

• cleanly obtained in 75% yield from triethyl phosphite and 3-chloro-2-methylpropene by addition of NaI [14]. Subsequent reduction of the ester with LiAlH4 and oxidation with IBX gave aldehyde 7 in 95% yield. Grignard addition of vinylmagnesium bromide afforded the alcohol 8, which comprised the desired

• triene system for an intramolecular Diels–Alder reaction. Oxidation of 8 with IBX changed the electronic properties of the system implementing an electron-deficient double bond suitable for a heat-induced intramolecular Diels–Alder reaction. The higher reaction temperature compared to the original

• ) rt, 45 min; e) IBX (3.0 equiv), EtOAc, reflux, 3 h; f) i) CH2=CHMgBr (1.5 equiv) Et2O, 0 °C, ii) rt, 20 min; g) IBX (3.0 equiv), EtOAc, reflux, 6 h; h) i) MeMgBr (1.5 equiv) Et2O, 0 °C, ii) rt, 30 min; j) NaOMe (25.0 equiv), MeOH, rt, 60 h. Enantioselective synthesis with (S)-Jørgensen’s

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• necessary (70% yield, 2:1 dr). The desaturation of the enone compound was next examined and while exposure of 13 to oxidant (o-iodoxybenzoic acid (IBX) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)) left the starting materials unchanged, treatment with NaH in the presence of oxygen to induce the

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• evolution (likely H2) occurred. However, no reduction of the amide was observed, even after stirring at room temperature for 24 hours. In an effort to “salvage” the reaction by reducing the amide to the corresponding N-benzylamine (which could potentially be oxidized to the corresponding imine with IBX [18

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• primary alcohol 99 (90%). Oxidation of this moiety with IBX to its corresponding aldehyde served as a substrate for the two-carbon homologation via Wittig reaction giving ester 96 in 80% yield over the two steps. After reduction of the ester group to its primary alcohol counterpart, the Sharpless

• ether 94 (90%) and the PMB ether was cleaved to liberate the primary alcohol. After being oxidized with IBX, the aldehyde 103 was isolated in 68% yield over two steps. Application of the asymmetric Brown’s allylation afforded 104 in 80% yield (dr 95:5) that was readily esterified to its cinnamate ester

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• % ee) (Scheme 10). A catalytic asymmetric β-C−H functionalization of ketones 33 with 4-hydroxycoumarins 1 was developed by Zhu et al. [43]. The enamine, formed via reaction of the aminocatalyst 35 with the ketone, is oxidased by IBX resulting in the electrophilic imine, which in turn undergoes a

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• starting material was recovered. Use of PCC resulted in product epimerization and so the method was abandoned. Success was achieved by use of IBX in DMSO, overnight, resulting in the recovery of a quantitative yield of 23 (Scheme 6). The amine was synthesized by first converting the primary alcohol to a

• %. Synthesis of ent-pavettamine as the TFA salt 28. Reaction conditions: a) IBX, DMSO, rt, overnight, quantitative yield; b) TsCl, DMAP, DCM, rt, 24 h, 83%; c) NaN3, DMF, 80 °C, 3 h, 75% yield; d) 10% Pd/C, H2, ethanol, rt, 12 h, quantitative yield; e) sodium triacetoxyborohydride, 1,2-DCE, THF, rt, 24 h, 95

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• the enantioselective β-arylation of cyclic ketones is known [38]. In 2017, Hu et al. presented the possibility of an enantioselective β-arylation of cyclohexanone using the above mentioned ligand L2. Cyclohexanone was in situ oxidized by 2-iodoxybenzoic acid (IBX) to 2-cyclohexenone, that subsequently

3-Acetoxy-fatty acid isoprenyl esters from androconia of the ithomiine butterfly Ithomia salapia

• Florian Mann,
• Daiane Szczerbowski,
• Lisa de Silva,
• Melanie McClure,
• Marianne Elias and
• Stefan Schulz

Beilstein J. Org. Chem. 2020, 16, 2776–2787, doi:10.3762/bjoc.16.228

• o-iodoxybenzoic acid (IBX) [31]. The resulting aldehyde was transformed into β-ketoacid 16 with ethyl diaazoacetate and SnCl2 [32], which upon reduction with NaBH4 in methanol delivered methyl 3-hydroxyoctadecanoate (17). Transesterification was performed with 3-methyl-3-buten-1-ol using distannoxan

• -enoate (12) was performed to verify the structural proposal and to determine the absolute configuration of the natural product (Scheme 4). The commercially available epoxide (S)-22 served as chiral starting material. 1,9-Nonanediol (19) was monobrominated and oxidized with IBX to yield 9-bromononanal (20

• ) and ithomiolide A (3). Biosynthetic formation of hedycaryol (7) and α-elemol (8). Synthesis of isoprenyl 3-acetoxyoctadecanoate (11). a) IBX, EtOAc, 60 °C, 3.15 h, 99%; b) SnCl2, CH2Cl2, rt, 70%; c) NaBH4, 12 h, 98%; d) SnOBu2, 140°C, 36 h, 78%; e) Ac2O, pyridine, DMAP, CH2Cl2, 12 h rt, 67%. a) 48

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• to be explored. The oxidants cerium(IV) ammonium nitrate (CAN), ferric chloride hexahydrate (FeCl3·6H2O), vanadium pentoxide (V2O5), PIFA, and PIDA, in addition to SnCl4, were considered. Also investigated were 2-iodoxybenzoic acid (IBX) because of its implication in single-electron oxidation [24

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner–Wadsworth–Emmons-based approach

• Rhys A. Lippa,
• John A. Murphy and
• Tim N. Barrett

Beilstein J. Org. Chem. 2020, 16, 1617–1626, doi:10.3762/bjoc.16.134

• varying amine structure, constituting potential Arg–Gly components of Arg–Gly–Asp integrin inhibitors (Table 3). Where the aldehyde was not commercially available, N-Boc-protected alcohols were oxidised using IBX in refluxing ethyl acetate and used crude. Olefination required only a modest excess of base

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• catalytic amount of azobis(isobutyronitrile) (AIBN) in CCl4 (Scheme 1c) [61][62]. In 2002, Nicolaou and co-workers found that ortho-iodoxybenzoic acid (IBX) could also effectively dehydrogenate chromanones to chromones (Scheme 1d, method 1) [63]. Moreover, active MnO2 was also found useful in the oxidative

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• explosive properties of Togni’s reagent and very recently, Williams and co-workers analyzed the sensitivity of common oxidants including 2-iodoxybenzoic acid (IBX) and Dess–Martin periodinane (DMP) [19][20]. Waser and co-workers examined the thermal stability of the Zhdankin reagent ABX and compared it with

Synthesis of acremines A, B and F and studies on the bisacremines

• Nils Winter and
• Dirk Trauner

Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219

• biogenetic precursor of acremines A (1) and B (2), we wanted to access these antifungal derivatives through selective oxidations. Indeed, treatment of 5 with IBX preferentially oxidized the C1-allylic alcohol, giving 1 in respectable yield. Prolonged treatment (9 h) of 5 with a large excess of IBX oxidized

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• tert-butyl ester 13a to the alcohol by portionwise addition of DIBAL and careful temperature control (slow warm-up from −78 to −30 °C) afforded the alcohol without α-epimerization, which was oxidized to aldehyde 15 (IBX, Scheme 3). Adamantyl ester 14 resisted reduction under the same conditions and was

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• place. Thus, we reduced the ester function of dienol triflate 11 to the alcohol (DIBAL-H, DCM, −78 °C), followed by oxidation to aldehyde 15 (IBX, Scheme 2). Fortunately, the cyclohexadiene moiety survived the oxidation conditions, which was not the case when using PCC or MnO2. Subsequent Sonogashira

• 18 to the acyloin (IBX, MeCN) and subsequent reduction (LiAlH4, THF, Scheme 2). Diastereomers 18 and 19 show distinct sets of NMR signals. The largest chemical shift differences are observed for the secondary carbinol group (δ2-H 5.18, δC2 73.1 for 18 vs δ2-H 4.14, δC2 87.2 for 19). For diol 18, we

The mechanochemical synthesis of quinazolin-4(3H)-ones by controlling the reactivity of IBX

• Md Toufique Alam,
• Saikat Maiti and
• Prasenjit Mal

Beilstein J. Org. Chem. 2018, 14, 2396–2403, doi:10.3762/bjoc.14.216

• intramolecular control. At maximum contact of the reacting substances, i.e., under solvent-free mechanochemical conditions, 2-aminobenzamides, aryl-, alkylaldehydes and the iodine(V) reagent o-iodoxybenzoic acid (IBX) led to substituted quinazolin-4(3H)-one derivatives in fair yields. Keywords: ball-mill

• ; contact explosive; IBX; mechanochemical synthesis; quinazolin-4(3H)-one; Introduction An iodine and ammonia mixture is a well-known contact explosive due to formation of NI3 [1]. Similarly, hypervalent iodines as oxidizing compounds [2] react violently with amines under solvent-free conditions [3

• focus on the development of synthetic methods using iodine-based reagents [21][22][23][24][25][26], we here report a method for the synthesis of quinazolin-4(3H)-ones [27][28] (Figure 1) from 2-aminobenzamide and aldehydes in the presence of o-iodoxybenzoic acid (IBX) [29]. However, when mixing

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• side. Towards this, the free secondary hydroxy group in 25 was masked as its corresponding TBDPS ether 26 and then treated with PPTS in MeOH [36] to afford the disilylated primary alcohol 27 in 95% yield. Treatment of alcohol 27 with IBX [37] furnished the corresponding aldehyde 14 which was subjected

• h, 95%; (c) IBX, THF/DMSO, 0 °C to rt, 1 h, 97%; (d) 15, n-BuLi, THF, −78 °C to rt, 2 h, 83%; (e) TBAF, THF, 0 °C to rt, 2 h, 85%. Synthesis of compound 25a. Reagents and conditions: (a) (R)-CBS catalyst, BH3·DMS, −50 °C, 16 h, 86%. Synthesis of strongylodiol I (10a). Reagents and conditions: (a) (i

• ) TBDPSCl, imidazole, CH2Cl2, 0 °C to rt, 1 h, 96%; (ii) PPTS, MeOH, 0 °C to rt, 2 h, 87%; (iii) IBX, DMSO/THF 1:1, 0 °C to rt, 1 h, 98%; (b) 16, n-BuLi, THF, −78 °C to rt, 2 h, 81%; (c) TBAF, THF, 0 °C to rt, 2 h, 82%. Comparison of 1H and 13C NMR data of strongylodiol H (isolated natural product vs

Hypervalent iodine compounds for anti-Markovnikov-type iodo-oxyimidation of vinylarenes

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Mikhail A. Syroeshkin,
• Alexander A. Korlyukov,
• Pavel V. Dorovatovskii,
• Yan V. Zubavichus,
• Gennady I. Nikishin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2018, 14, 2146–2155, doi:10.3762/bjoc.14.188

• the examined hypervalent iodine oxidants (PIDA, PIFA, IBX, DMP) PhI(OAc)2 proved to be the most effective; yields of iodo-oxyimides are 34–91%. A plausible reaction pathway includes the addition of an imide-N-oxyl radical to the double C=C bond and trapping of the resultant benzylic radical by iodine

• %) was obtained using PhI(OAc)2 (Table 1, entry 2). Other iodine-based oxidants, such as PhI(OCOCF3)2 (Table 1, entry 10, yield 31%), IBX (Table 1, entries 11 and 12, yield 32–54%), DMP (Table 1, entries 13–14, yield 52%), showed less efficacy in this process. Peroxide oxidants, such as TBHP, TBAI/TBHP

• mmol) was added. In the additional experiments compounds 3ca and 3ga were prepared using IBX (140 mg, 0.50 mmol) or DMP (64 mg, 0.15 mmol) instead of PhI(OAc)2. After stirring for 10 min under air atmosphere at 20–25 °С, CH2Cl2 (30 mL) was added. The resulting mixture was washed with an aqueous

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• oxidants are employed. For example, the oxidation of alcohols to carbonyls traditionally requires strong oxidants (Cr(VI) species, IBX, DMP), whereas similar reactions using photochemical methods can utilise oxygen (O2) as the oxidising agent. The oxidising agent can accept electrons either from the

Preparation and X-ray structure of 2-iodoxybenzenesulfonic acid (IBS) – a powerful hypervalent iodine(V) oxidant

• Irina A. Mironova,
• Pavel S. Postnikov,
• Rosa Y. Yusubova,
• Akira Yoshimura,
• Thomas Wirth,
• Viktor V. Zhdankin,
• Victor N. Nemykin and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 1854–1858, doi:10.3762/bjoc.14.159

• hypervalent iodine compounds as stoichiometric reagents or catalysts has experienced an explosive growth [1][2][3][4][5][6][7][8]. Hypervalent iodine(V) compounds represent an important class of oxidative reagents extensively employed in organic synthesis [9][10][11]. 2-Iodoxybenzoic acid (IBX) and the

• product of its acetylation Dess–Martin periodinane (DMP) are the most common oxidants used for selective oxidation of alcohols to carbonyl compounds as well as for a variety of other synthetically useful oxidative transformations [10][11]. IBX and DMP are mild oxidants with a relatively low reactivity

• alcohols based on 2-iodoxybenzenesulfonic acid (IBS) as the active species [12][13]. IBS (or its sodium salt) is much more active as catalyst than IBX derivatives. In particular, it can be used as a highly efficient and selective catalyst (0.05–5 mol %) for the oxidation of primary and secondary alcohols

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• -catalyzed 1,2-acetoxysulfenylation of Baylis–Hillman products at 50 °C under an oxygen atmosphere as shown in Scheme 35 [70]. The β-ketomethylene 94 substrate was generated in situ from the oxidation of Baylis–Hillman product 93 using a hypervalent iodine reagent (iodoxybenzoic acid, IBX) in an ionic liquid

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• ]. Review Tandem additions λ5-Iodanes such as the Dess–Martin periodinane or IBX [26], and λ3-iodanes such as benziodoxolones [27], are versatile reagents in organic synthesis. These are often used, respectively, for the oxidation of alcohols or carbonyl compounds, and in atom-transfer reactions. These

• of the first studies documenting the use of the iodoarene moiety as a building block in synthesis has been reported in 2004. The λ5-iodane reagent IBX has been shown to promote the α-functionalization of ketones following the introduction of the 2-iodobenzoic acid motif (Scheme 2a) [28]. Mono- and

• stereoselective trans iodo-benzoylation of glycals using a combination of IBX and molecular iodine, that is considered as a source of I+ formed from the in situ generated hypoiodite species [30]. The controlled oxidation of various N-(alkyl)- and N-(aryl)pyrroles with Dess–Martin periodinane also leads to

Rapid transformation of sulfinate salts into sulfonates promoted by a hypervalent iodine(III) reagent

• Elsa Deruer,
• Vincent Hamel,
• Samuel Blais and
• Sylvain Canesi

Beilstein J. Org. Chem. 2018, 14, 1203–1207, doi:10.3762/bjoc.14.101

• ). To verify our hypothesis tosyl-sulfinate 1 was treated with iodanes such as sodium periodate (NaIO4), Dess-Martin periodinane (DMP) [33], 2-iodoxybenzoic acid (IBX) [34], (diacetoxyiodo)benzene (DIB), phenyliodine(III) bis(trifluoroacetate) (PIFA) in the presence of methanol. (III)-Iodanes and (V

• )-iodanes were both acceptable substrates, but the process was inefficient with (VII)-iodane species. We surmise that IBX and DMP are rapidly reduced to a (III)-iodane in the presence of an alcohol, and that this species is most likely the reagent promoting the formation of compound 4a. Iodine and N

• -iodosuccinimide (NIS) were also tested; it appeared that this process was much more efficient in the presence of iodane sources (Table 1). DIB was chosen as the hypervalent iodine reagent of choice since it is more compatible with alcohols than IBX or DMP. The reaction proceeded in modest to good yields depending

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

• repeated the synthesis of 12 through a molecular bromination–dehydrobromination sequence starting with 162 [137]. Hypervalent iodine(V)-based reagents such as IBX (or 2-iodoxybenzoic acid) and Dess–Martin periodinane (DMP) are commonly used in organic synthesis as oxidizing agent to form both unsaturated

• carbonyl compounds and conjugated aromatic carbonyl systems. Nicolaou’s group reported a general method for the mild, swift, and highly efficient oxidation of alcohols, ketones, and aldehydes to unsaturated compounds in one pot (Scheme 30) [138][139]. Accordingly, an IBX-controlled dehydrogenation through