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

• who want to know the chemistry involved during the dearomatization of phenols and to find the relevant literature available until 2008. In this review article, various approaches for the synthesis of spirocyclic scaffolds using hypervalent iodine reagents are covered including stereoselective

• reactions. Hypervalent iodine reagents are mainly popular for their oxidative properties but various iodine(III) reagents have been used as electrophiles. Numerous iodine(III) reagents have been successfully used to achieve diverse spirocyclic scaffolds. Phenols 7 or 11 having an internal nucleophile at

• oxidation of iodoarene using mCPBA as terminal oxidant [76]. In this report, p-substituted phenols 27 were cyclized to the corresponding spirolactones 29 using iodotoluene 33 as precatalyst, mCPBA as oxidant and TFA as an additive. The spirolactones 29 were isolated as reaction products in excellent yields

Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents

• Ugo Azzena,
• Massimo Carraro,
• Gloria Modugno,
• Luisa Pisano and
• Luigi Urtis

Beilstein J. Org. Chem. 2018, 14, 1655–1659, doi:10.3762/bjoc.14.141

• employed reactions is a challenge in contemporary organic chemistry. We applied such an approach to the synthesis and further conversion of tetrahydropyranyl ethers, an important class of compounds widely employed in multistep syntheses. Several alcohols and phenols were almost quantitatively converted

• tetrahydropyranylation of alcohols and phenols in cyclopentyl methyl ether (CPME) and 2-methyltetrahydrofuran (2-MeTHF) in the presence of heterogeneous acidic catalysts. Indeed, both CPME [19][20][21][22] and 2-MeTHF [21][22][23][24][25] are characterized by relatively high boiling points, a narrow explosion range

• phenols, including some known fragrances (3g–j and 3l) [4][5][6][7], as illustrated in Scheme 2. Conversions exceeding 95% were achieved under the mild conditions illustrated in Scheme 2 with primary aliphatic and benzylic alcohols 1b–h. A notable exception is the low conversion of 4-bromobenzyl alcohol

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• or secondary alcohols, while the nucleophilic species needs to be acidic [13] with a pKa < 11. Otherwise the azo reagent would compete with the acidic nucleophile and participate in the substitution reaction [14]. Various compounds comply with that condition: carboxylic acids, phenols, hydrazoic acid

• phenols to achieve aryl glycosides Not only anomeric esters, but also glycosides can be obtained through the Mitsunobu reaction. Dehydrative glycosylation approaches with reducing sugars were previously reviewed [43][44]. As phenols are weak acids, they are suitable reaction partners in the Mitsunobu

• photoswitchable azobenzene α-D-mannoside 47 (Scheme 9) [46]. Notably, in this reaction, traces of an anomeric mixture of the respective furanoside 48 were detected. The Mitsunobu synthesis of aryl glycosides was also applied to p-nitrophenol [47], naphthols [48][49], or multifunctional phenols [27][50]. Such

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

• , C–C, C–O, or C–N couplings, dearomatization of phenols, rearrangements, to name but a few, have been reported using these compounds thereby reflecting their versatility. A survey of the general structure of polyvalent organoiodine compounds reveals that they are prepared mostly from iodoarene

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• -arylations of phenols using diaryliodonium salts [23][24][25], which are reactive electrophilic arylation reagents [26][27][28]. As diaryliodonium salts can be easily synthesized in a one-pot manner [28], we envisioned that phenoxazines could be obtained in a straightforward and efficient manner from

• sequence, proceeding via arylation of phenols with diaryliodonium salts using our reported methodology [23][24][25]. In reactions with unsymmetrical iodonium salts, this type of O-arylation is known to have an ortho-effect, i.e., chemoselective transfer of the ortho-substituted aryl moiety [29][30]. The

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

• temporary generate potentially unstable λ3-iodane derivatives and immediately convert them under the established α-arylation conditions. A PIDA ((diacetoxyiodo)benzene)-mediated ortho-iodination/O-arylation cascade was developed by Panda and co-workers using diversely functionalised phenols 23 (Scheme 14

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• oxylation of ketones reported by Masson et al. α-Fluorination of β-keto esters. Alkynylation of β-ketoesters and amides catalyzed by phase-transfer catalyst. Alkynylation of β-ketoesters and dearomative alkynylation of phenols. Acknowledgements The authors highly acknowledge the financial assistance

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

• Discussion Oxidative sulfonate production methods employing strong oxidizing agents such as chlorine have been previously reported [30]. More recently, a mild and efficient method enabling the production of aromatic sulfonates using phenols and iodine was developed [31][32]. This method uses methanol as a

• solvent and appears to be selective for phenols; only two primary alcohol examples were produced in 63–67% yield in the presence of a strong base. A radical pathway from the alkoxide species was proposed by the authors as an explanation for the phenol selectivity under weakly basic conditions in the

• compatible in presence of phenols. We hypothesized that the mechanism would initially involve iodane activation of the sulfur lone pair leading to 2. Elimination of the iodane would subsequently produce the sulfonium ion 3, which could be trapped by an alcohol nucleophile leading to sulfonate 4 (Scheme 1

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

• Eirinaios I. Vrettos,
• Gábor Mező and
• Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

One-pot synthesis of diaryliodonium salts from arenes and aryl iodides with Oxone–sulfuric acid

• Natalia Soldatova,
• Pavel Postnikov,
• Olga Kukurina,
• Viktor V. Zhdankin,
• Akira Yoshimura,
• Thomas Wirth and
• Mekhman S. Yusubov

Beilstein J. Org. Chem. 2018, 14, 849–855, doi:10.3762/bjoc.14.70

• the generation of iodine(III) species in the oxidation of phenols [43]. In the present work, we report the development of a reliable and convenient procedure for the preparation of diaryliodonium bromides using Oxone in the presence of sulfuric acid. Results and Discussion After having investigated

Enantioselective dioxytosylation of styrenes using lactate-based chiral hypervalent iodine(III)

• Morifumi Fujita,
• Koki Miura and
• Takashi Sugimura

Beilstein J. Org. Chem. 2018, 14, 659–663, doi:10.3762/bjoc.14.53

• iodine reagents using a lactate motif has been employed for several types of oxidation reaction since we first reported this procedure [18]. Enantioselective oxidative transformations include the dearomatization of phenols [19][20][21][22][23][24], α-functionalization of carbonyl compounds [25][26][27

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• . This results in differences in both the formation and stability of o-QM. Grimaud et al. synthesized Mannich bases starting from N-benzylpiperazine, various aldehydes and substituted phenols [63]. The intermediate Mannich adducts 8a–i were then reacted with 5,5-dimethylcyclohexane-1,3-dione or 1-methyl

• ortho-amidoalkylation of phenols in which a tandem Knoevenagel condensation occurs through o-QM followed by the formation of an unstable oxazine intermediate [64]. Later, the same research group published a similar reaction extended by various lactams carried out in trifluoroacetic acid in water [65

• wide range of novel 2-[(benzo[d]thiazol-2-ylamino(phenyl)methyl]phenols 10a–m [66]. In their study, 2-amino-1,3-benzothiazoles, various aldehydes and substituted phenols were reacted in the presence of ZnCl2 as catalyst. Reactions of o-QMs formed by Mannich bases As the formation of Mannich bases can

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• terminal oxidants [14]. The protocol was also extended to reactions with 2-alkylquinoline [15] and phenols [16] using O2 and di-tert-butyl peroxide (DTBP) as oxidant, respectively (Scheme 1). A CuCl-catalyzed oxidative cross coupling of glycine derivatives with indoles has been developed by Hou et al

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• ], antitumor [1], antiasthmatic [12], and antiviral including anti-HIV [13][14]. Comprehensive synthetic studies of coumarins and their derivatives have been carried out [15][16]. Typically, coumarins are prepared by the acid-catalyzed condensation of 2-alkynoic acids and phenols or the condensation of β

• -ketoesters and phenols (the Pechmann condensation) [17]. Recent studies for the metal-catalyzed reactions for the synthesis of the coumarin skeleton are as follows: the Yb(OTf)3-catalyzed microwave irradiation of phenols and propynoic acids [18], the Pd(OAc)2-catalyzed oxidative cyclocarbonylation of 2

• acid-catalyzed reaction of phenols and propynoic acids [22] and the (−)-riboflavin-catalyzed photochemical reaction of cinnamic acids [23] were reported recently. Moreover, the use of radical cyclization for the construction of the coumarin skeleton has become widespread. Examples include the radical

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• coupled with various phenols 152 at the more reactive 7-position under mild reaction conditions in presence of K2CO3 in acetic acid/DMF to give pyrazolo[1,5-a]pyrimidine derivative 153. Various aromatic amines 154 were then coupled at 5-postion under Buchwald–Hartwig conditions to get the desired 5

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• catalytic amount of copper salt was required in this reaction. The hydrogens on the ortho and para positions of phenols have higher reactivity. Thus, undesired side reactions were often involved in the trifluoromethylation of less substituted phenols, including oxidative dimerization and oligomerization

• . Although phenols were widely used building blocks in bioactive compounds, only a few examples introducing a CF3 have been reported. In 2015, the group of Hamashima [52] achieved a direct C–H trifluoromethylation of phenol derivatives with high regioselectivity. The CF3 was selectively incorporated into the

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• limits [36]. Their origin by biomethylation of the corresponding phenols is frequently discussed, but the de novo formation of compounds 14 and 15 without administration of the corresponding phenols has not been reported before. Volatiles from Daldinia clavata identified by synthesis Several other

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• phenols. Mono- and dichlorination of carbon acids. Monochlorination of (N-aryl-N-hydroxy)acylacetamides. Examples of the synthesis of heterocycles fused with β-lactams through a chlorination/cyclisation process. Enantioselective chlorination of β-ketoesters and oxindoles. Enantioselective chlorination of

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• for the synthesis of 4-methoxycarbonylcoumarins by reaction of dimethyl acetylenedicarboxylate and triphenylphosphine with substituted phenols. The vinyltriphenylphosphonium salt 106 that is formed as an intermediate product was attacked by the nucleophilic carbon atom of the phenolate anion, which

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• , benzaldehydes and electron-rich phenols in presence of 5 mol % of POPI, afforded near quantitative yield of chromene derivatives within 20 min (Scheme 40). Similarly, various benzaldehydes with electron-withdrawing groups at the o/p-position accelerated the reaction and electron-donating groups slowed that down

Selective enzymatic esterification of lignin model compounds in the ball mill

• Ulla Weißbach,
• Saumya Dabral,
• Laure Konnert,
• Carsten Bolm and
• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1788–1795, doi:10.3762/bjoc.13.173

• down the acetylation of erythro-1a. A plausible explanation could be the nature of the 2,2’-biphenol moiety, which could have acted as a ligand interfering with the enzyme. The resilience of CALB to phenols is in agreement with the high reactivity observed when phenyl acetate (2c), erythro-1a and CALB

• the lower reactivity towards the esterification of the substrate containing a phenolic substituent 1f. Although it is known that lignin samples contain units bearing aromatic phenols, these phenolic fragments are mostly located at the terminal sides of the biopolymer. Therefore, enzymatically

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• dearomatization of phenols and naphthols. Ishihara’s ammonium salt-catalysed oxidative cycloetherification. Chiral phase-transfer-catalysed α-sulfanylation reactions. Chiral phase-transfer-catalysed α-trifluoromethylthiolation of β-ketoesters 1. Chiral phase-transfer-catalysed α-amination of β-ketoesters 1 using

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• the presence of silver oxide), phenols 4 and 5 were converted into the alkaloids 2 and 3 in 33 and 49% yields (Scheme 9). In accordance to Kunitomo’s observations, the isomeric methoxy compounds 18 and 19 were obtained as byproducts in significant yields (Scheme 9). In order to find a more convenient

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• substituted phenols. Reactions of monobrominated substrates. Rotational barriers of substrates and intermediates calculated at the B3YLP/6-31G(d) level of theory. Reaction of substrate with protected phenol. Optimization of conditions.a Supporting Information Supporting Information File 257: Experimental

Urea–hydrogen peroxide prompted the selective and controlled oxidation of thioglycosides into sulfoxides and sulfones

• Adesh Kumar Singh,
• Varsha Tiwari,
• Kunj Bihari Mishra,
• Surabhi Gupta and
• Jeyakumar Kandasamy

Beilstein J. Org. Chem. 2017, 13, 1139–1144, doi:10.3762/bjoc.13.113

• available, inexpensive and nontoxic. The application of UHP as oxidant is well explored in various solution- as well as solid-phase organic syntheses [25][26][27][28]. In fact, we have recently reported the oxidation of arylboronic acids into corresponding phenols by using UHP as a selective oxidizing agent