Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• the erythrinadienone intermediate 182. On contrary, common scaffold 180 should hydrolyze to sebiferine-type scaffolds in the presence of water. Taking these results into account, the group exploited the ability of HFIP to stabilize the radical cation formed by PIFA and BF3·EtO2 [95][96] to selectively

• produce aporphine natural products, while the use of PIDA or PIFA in the presence of BF3·OEt or TMSOTf in wet CH3CN allows to diverge the synthesis to morphinandienone natural products (e.g., 181, Scheme 15). The flow reaction was performed in a reaction coil at room temperature. Two reaction loops were

• used. The first one was loaded with the substrate and the second with PIFA and BF3·EtO2, while HFIP was used as the solvent. The two streams were mixed in a T-mixer, equipped with a 250 μL frit, to ensure efficient mixing. Under the optimized conditions, the method provided aporphine products in good

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• developed based on other oxidizing agents, such as cobalt(III) fluoride [85], phenyliodine(III) bis(trifluoroacetate) (PIFA) [86] and tert-butyl hydroperoxide [87] (Table 3). In 1999, Tomatsu and co-workers performed the synthesis of menadione (10) through demethylation of 2-methyl-1,4-dimethoxynaphthalene

• published an alternative and sustainable methodology, using phenyliodine(III) bis(trifluoroacetate) (PIFA) as an oxidizing agent of the demethylation reaction [86]. The hypervalent iodine(III) proved to be a good oxidizing agent in the formation of 10 (92% yield) (Table 3, entry 2). According to the authors

• , this is a good synthetic path, since PIFA has a low toxicity and it is easily accessible. Subsequently, Wójtowicz and co-workers studied a series of experiments in order to test the oxidative action of tert-butyl hydroperoxide and the role of organoselenes as catalysts in the demethylation reaction of

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• on PIFA-initiated oxidative 5-exo-trig cyclization of 2-(3-butenyl)quinazolin-4(3Н)-ones, in turn prepared by thermal cyclocondensation of the corresponding 2-(pent-4-enamido)benzamides. The products obtained have a good natural product likeness (NPL) score and therefore can be useful for the design

• of natural product-like compound libraries. Keywords: [bis(trifluoroacetoxy)iodo]benzene PIFA; nitrogen heterocycles; oxidative cyclization; pyrrolo[1,2-a]quinazolines; Introduction An important design concept in current drug discovery includes structural modifications of naturally occurring

• )-ones 7 upon action of bis(trifluoroacetoxy)iodobenzene (PIFA) (see Scheme 1D). A part from the well-known applications of hypervalent iodine compounds for oxidative rearrangements, fragmentations, halogenations and hydroxylations [37][38], they were also involved in the synthesis of N-heterocycles [39

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• independently disclosed a photocatalytic cyanomethylarylation of N-aryl/benzoyl acrylamide for the synthesis of oxindoles and isoquinolinediones using diazonium salts and PIFA/1,3,5-trimethoxybenzene as radical initiators, respectively [29][30][31]. In this case, expensive Ru and 4CzIPN-based homogeneous

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• inverse electron-demand Diels–Alder cycloaddition reactions between a dibenzosuberenone and tetrazines that bear various substituents. The pyridazines were synthesized in high yields by oxidation of dihydropyridazine-appended dibenzosuberenones with PIFA or NO. p-Quinone derivatives of pyridazines were

• , dihydropyridazines 3a–f were oxidized to pyridazines. In contrast to dihydropyridazineamide 3e, the reaction of dihydropyridazines 3a–d and 3f with PIFA ([bis(trifluoroacetoxy)iodo]benzene) afforded the corresponding pyridazine derivatives 4a–d and 4f in good yields (79–95%). As a result of the reaction of PIFA with

• and the p-quinone methides part was reduced to phenol. After the phenolic part of 13a,b was oxidized to p-quinone methides with PIFA, 14a and 14b were synthesized in 87% and 91% yields, respectively. Moreover, by submitting 13a,b to reductive conditions in presence of Zn, the pyridazine part of 13a,b

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

• oxidative dimerization of 1,2,4-trimethoxynaphthalene under anhydrous conditions using CAN, PIDA in BF3·OEt2 or PIFA in BF3·OEt2 in 7–8% yields over 3 steps. Ellagic acid is synthesized from its biosynthetic precursor gallic acid, in 83% yield over 2 steps. Keywords: balsaminone A; biomimetic synthesis

• phenyliodine diacetate (PIDA) and phenyliodine bis(trifluoroacetate) (PIFA), have been utilized for oxidative dimerization reactions [14][15]. The use of these one-electron oxidants, as well as non-metallic reagents, plays an important role in accessing symmetrical and asymmetrical biaryls and polyaryls [1

• 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

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• (trifluoroacetoxy)iodo]benzene] (PIFA) and BF3·OEt2 in dichloromethane at −78 °C afforded, after 12 h, the desired cyclized product 8a in 59% yield. The reaction could be performed on a 0.5 mmol scale in a similar yield of 58%. Note that other typical reagents used for the Scholl reaction, such as DDQ/CF3CO2H

• , FeCl3, Cu(OTf)2, and AlCl3 failed to promote the cyclization of 7a to 8a. The PIFA/BF3·OEt2 system also promoted the Scholl reaction of terphenyl 7b bearing a methylenedioxy moiety with a comparable efficiency to afford 8b in 56% yield. Compound 8c, a naphthylene-linked analogue of 8a, also underwent

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

• generation of some unidentified byproducts. A solvent screening identified DMF to be the most appropriate solvent for this transformation (Table 1, entries 1–9). Other commonly employed oxidants, including phenyliodine(III) diacetate (PIDA), phenyliodine(III) bis(trifluoroacetate) (PIFA), and iodylbenzene

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

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• spirolactones 29. The reaction products were obtained in excellent yields using 0.55 equivalents of bridged iodine(III) reagent 28 in acetonitrile at room temperature (Scheme 6). Furthermore, a comparative study was done between bridged iodine(III) reagent 28 with PIFA. It was found that the reaction products

• 29 were obtained in higher yield using the bridged iodine(III) reagent compared to that using PIFA. Probably, the iodine-OCOCF3 bond of the bridged compound 28 has a significant ionic character as the iodine–oxygen bond distance is larger than in PIFA which intends to make it more reactive than PIFA

• . PIFA (31) is a more electrophilic iodine(III) reagent than PIDA (15) due to the presence of two trifluoroacetoxy groups. There are some approaches for the synthesis of spirocyclic compounds where PIFA (31) is used as electrophile. Recently, Lewis and co-workers [73] reported the conversion of arnottin

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• subjected to the Pummerer-type glycosylation mediated by hypervalent iodine. Treatment of 36 with bis(trifluoroacetoxy)iodobenzene (PIFA) and uracil in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) and triethylamine gave a 5:1 mixture of 4’-thiouridine derivative 37 in 55% yield. The

• %) (Table 1, entry 2). The use of more reactive hypervalent iodine agents (PIFA and diacetoxyiodobenzene) did not improve the chemical yield of 75 (Table 1, entries 3 and 4). When 73 was treated with iodosylbenzene, TMSOTf, 2,6-lutidine and the silylated uracil in dichloroethane at 50 °C, the reaction gave

• 91b in 45% and 49% yields respectively (Table 2, entries 1 and 2). On the other hand, the use of trialkylsilanes 90a and 90b successfully improved the chemical yield of 91a and 91b (Table 2, entries 3 and 4). In contrast, the reactions using PIFA, iodosylbenzene, and [hydroxyl(tosyloxy)iodo]benzene

Synthesis of trifluoromethylated 2H-azirines through Togni reagent-mediated trifluoromethylation followed by PhIO-mediated azirination

• Jiyun Sun,
• Xiaohua Zhen,
• Huaibin Ge,
• Guangtao Zhang,
• Xuechan An and
• Yunfei Du

Beilstein J. Org. Chem. 2018, 14, 1452–1458, doi:10.3762/bjoc.14.123

• and phenyliodine bis(trifluoroacetate) (PIFA) were tested, but the results indicated that they were ineffective to further improve the yields (Table 1, entries 11 and 12). With the optimized conditions in hand, we next explored the substrate scope for this newly established one-pot oxidative

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• describe an efficient α-arylation of a variety of 1,3-dicarbonyl derivatives 21 using [bis(trifluoroacetoxy)iodo]benzene (20a, PIFA). In this metal-free approach the target structures 22 are efficiently synthesised even without any initial prefunctionalisation of the arene moiety (Scheme 13). Remarkably

• , the intact 2-iodoaryl group is transferred via presumed transition state TS1, which leads to a good AE (50% for 22a) and allows the further transformation of the α-arylation product 22 via cross coupling reactions. In addition, the in situ generation of the PIFA reagent proved viable, in order 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

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• )iodobenzene (DIB) and lithium bromide yield a dibromo adduct (Scheme 1, reaction 2), whereas a combination of (bis(trifluoroacetoxy)iodo)benzene (PIFA) and tetra-n-butylammonium bromide (TBAB) gives bromo(trifluoro)acetoxylated 3a (Scheme 1, reaction 3) [16]. We then decided to further explore the synthetic

• requires the use of a PIFA/TBAB combination in a 1:1 ratio with slow addition of the latter to the reaction mixture thereby preventing the formation of 2a. In this fashion, bromo(trifluoro)acetoxy adduct 3a was obtained in 77% yield (Table 1, entry 2). The reaction course can also be modified by changing

• case the analogous bromoethoxylated adduct 4a’ could be isolated in 68% yield, albeit along with 25% of 2a (Table 1, entry 6). Turning our attention to iodination, we first used the combination of PIFA and KI that had given the best results with enamides [13]. Thus, iodo(trifluoro)acetoxylated adduct

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• ), phenyliodine(III) bis(trifluoroacetate) (PIFA), and iodosobenzene, has since become a popular choice for benzylic oxidations, which further expanded the scope and availability of methods for direct C–H functionalization and several coupling reactions [42][43][44][45][46][47][48][49][50]. As such, we reported

• initiated by the decomposition of PIFA to form the trifluoroacetoxy radical under visible light irradiation [50]. Our approach for the generation of radical species for the benzylic carboxylation using a hypervalent iodine reagent relies on the unique reactivity of the hypervalent iodine(III)–bromine bond

• determined to be the best in terms of product yield. No reaction was observed in the absence of sodium bromide (Table 1, entry 9) and other representative hypervalent iodine(III) reagents, such as PIFA and PhI(OH)OTs, and pentavalent Dess–Martin periodinane and IBX, were inferior for this carboxylation when

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• 3a albeit in low yield (Table 1, entry 1). The background reaction mediated by a Lewis acid seemed plausible via an electrophilic activation of the double bond. When the reaction is performed in the presence of hypervalent iodine reagents such as PIFA ([bis(trifluoroacetoxy)iodo]benzene), PhI(NPhth)2

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

• persulfate by hypervalent iodine oxidants such as iodobenzene diacetate (PIDA, Scheme 28) [49], or iodobenzene bis(trifluoroacetate) (PIFA) [50]. Fu and co-workers proposed the reaction mechanism depicted in Scheme 28. PIDA reacted with CF3SO2Na under heating conditions to produce two radicals: CF3• along

• . Experimental and computational studies allowed the authors to propose the mechanism depicted in Scheme 32. First, the CF3 radical was generated from CF3SO2Na and PIFA. Then, addition of CF3• to the alkene gave the alkyl radical 59 that added to the ipso position of the heteroaryl group to form radical 60. Next

• , homolysis of the C–C σ-bond in 60 provided the more stable hydroxyalkyl radical 61. This radical was oxidised by PIFA to yield the cationic intermediate 62, which finally lost a proton to furnish the reaction product. 1,2-Bis-trifluoromethylation of alkenes: Alkenes were efficiently and chemoselectively bis

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

• reagent. The reaction temperature and residence time are 80 °C and 3.5 min, respectively. This product further undergoes a coupling reaction in a packed column containing polymer-supported [bis(trifluoroacetoxy)iodo]benzene (PS-PIFA), which yields a seven-membered tricyclic intermediate with 50% yield

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• demonstrated that this in situ generated reagent works more efficiently in such cyclizations than the more frequently used PIFA reagent. For instance, cyclization of biaryl 35 to carbazole 36 was achieved using this indirect electrochemical approach (Scheme 14) [59][60]. The transformation represents the key

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

• Raoni S. B. Gonçalves,
• Michael Dos Santos,
• Guillaume Bernadat,
• Danièle Bonnet-Delpon and
• Benoit Crousse

Beilstein J. Org. Chem. 2013, 9, 2387–2394, doi:10.3762/bjoc.9.275

• available reagents have been employed under metal-free conditions. A group [27] reported that the hypervalent iodine reagents (diacetoxyiodo)benzene (DIB) and phenyliodine bis(trifluoroacetate) (PIFA) could successfully promote the oxidation of aldoximes to the corresponding nitrile oxide. Those reagents

• 2 with PIFA in CH2Cl2 afforded the product in only 16% yield (Table 1, entry 4). Better results were obtained by employing DIB in CH2Cl2 as solvent, after which the product could be isolated in an acceptable yield (55%, Table 1, entry 3). [Bis(acetoxy)iodo]benzene (DIB) is a weaker oxidant than PIFA

Synthesis of the tetracyclic core of Illicium sesquiterpenes using an organocatalyzed asymmetric Robinson annulation

• Lynnie Trzoss,
• Jing Xu,
• Michelle H. Lacoske and
• Emmanuel A. Theodorakis

Beilstein J. Org. Chem. 2013, 9, 1135–1140, doi:10.3762/bjoc.9.126

• ) reductive deoxygenation with LiEt3BH (super hydride). The thioketal protecting group was then removed under oxidative conditions with [bis(trifluoroacetoxy)iodo]benzene (PIFA) to yield ketone 10 in good yield (66% over three steps, Scheme 2) [78]. This approach allowed us to produce a sufficient amount of

Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy

• Huili Liu,
• Kuan Zheng,
• Xiang Lu,
• Xiaoxia Wang and
• Ran Hong

Beilstein J. Org. Chem. 2013, 9, 983–990, doi:10.3762/bjoc.9.113

• 321004, China 10.3762/bjoc.9.113 Abstract A “stop-and-flow” strategy was developed for the chemoselective dioxygenation of alkenes with a PIFA-initiated cyclization. This method is conceived for the desymmetrization of seco-diene, and a series of substituted 5-hydroxymethyl-γ-lactones were constructed

• after hydrolysis. This strategy also differentiates terminally substituted alkenes and constitutes a potentially novel synthetic approach for the efficient synthesis toward velbanamine. Keywords: alkene; desymmetrization; dioxygenation; lactone; PIFA; velbanamine; Introduction Stictosidine-derived

• Recently, Tellitu, Dominguez, and co-workers reported an intramolecular oxyamidation of alkene 11 with phenyliodine(III)-bis(trifluoroacetate) (PIFA) (Scheme 3) [46]. The lactam 12 was originally assigned as an unstable intermediate, which should be subsequently reduced to pyrrolidine 13. It was

Diels- Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

• Natsuno Etomi,
• Takuya Kumamoto,
• Waka Nakanishi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2008, 4, No. 15, doi:10.3762/bjoc.4.15

• indanetrione 8, but attempts with bromoindanone 18 resulted in no reaction even under reflux. Utilization of a milder oxidant phenyliodosyl bis(trifluoroacetate) (PIFA) [33] for the oxidation of phenolic indanone 20, derived from 18 by selective demethylation with magnesium iodide (MgI2) [34], gave

• bromoquinone 12 after modification of the workup protocol without aqueous sodium bicarbonate. The PIFA oxidation of phenols 19 [35] and 20 in the presence of methanol gave the corresponding monoacetals 13 and 14. DAR of indanetrione 8 and 1-methoxy-1,3-butadiene (7) in dichloromethane (CH2Cl2) proceeded

• : a) P2O5, CH3SO3H, CH2Cl2 or CHCl3 (67% for 17, 71% for 18); b) bromine, 1,4-dioxane, H2O, rt, 2 h (68%); c) CAN, CH3CN, H2O, 0 °C, 30 min (65%); d) MgI2 · 6H2O, benzene, Dean-Stark (81% for 19, 96% for 20); e) PIFA, H2O, CH3CN, rt, 30 min (86%); f) PIFA, CH3OH, CH3CN, 0 °C (74% for 13, 92% for 14