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

• electrophilicity and appreciable oxidizing properties. The transformations associated with asymmetric induction mainly focused on the asymmetric oxidation and oxidative dearomatization chemistry. Asymmetric difunctionalization of alkenes, α-functionalization of carbonyls and also some typical 1,2-aryl

• displacement of the aryl iodide by the CO2R group in 77 leading to chiral lactones of type 78 [56]. Rearrangement strategy Wirth et al. used I(III) reagent 8b for the development of a stereoselective oxidative rearrangement method to synthesize α-arylated carbonyls 81 from α,β-unsaturated carbonyls 80 (Scheme

• reactive organostannane derived Sn–I(III) exchange in the presence of BF3·Et2O was the crucial step in the synthesis of the chiral iodonium salts from 88. In view of developing asymmetric α-arylations of carbonyls, Olofsson et al. has independently synthesized a new class of diaryliodonium salts 14 with

Addition of dithi(ol)anylium tetrafluoroborates to α,β-unsaturated ketones

• Yu-Chieh Huang,
• An Nguyen,
• Simone Gräßle,
• Sylvia Vanderheiden,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2018, 14, 515–522, doi:10.3762/bjoc.14.37

• dithiolanes by addition of an ynone to α-alkyl or aryl-substitued dithiolanylium TFBs. Keywords: addition to α,β-unsaturated carbonyls; dithiane chemistry; dithianylium tetrafluoroborate (TFB); ketene dithiane; Introduction 1,3-Dithioacetals are a common motif in organic chemistry. They are part of

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• of 4 equivalents of the thiol is needed for the reaction. The authors addressed this limitation in a later report (vide infra). Functional groups like alcohols, Boc-protected amines, carbonyls, esters and halides are tolerated. One year later, Yoon and co-workers described a redox mediator concept

• alkynes, bearing electron-donating (methyl, methoxy, amine or hydroxy) and withdrawing substituents (halides, carbonyls or sulfonamides) and also heterocyclic substrates. Various aromatic sulfinic acids could be applied, including methoxy, halogen, trifluoromethyl or acetylamino-substituted benzenes, as

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

• -trifluoromethylated carbonyls in low to moderate yields (Scheme 1) [8]. Nonetheless, important competition between the introduction of the CF3 group or a Cl atom was invariably observed in various ratio depending on the nature of the substrates. As for the mechanism of the reaction, the authors proposed a radical

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• carbonyls 2 and 3 show distinctly weaker fluorescence than the pyrene alcohols 4 and 5. The quantum yields at ambient temperature are at least 20 times lower than for 4 and 5. The decay times drop to below 2 ns (Table 1). Similar trends were already observed for 1-acetylpyrene [31]. In the latter case, low

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• keto carbonyl (δC 202.6), two amide carbonyls (δC 175.5, 175.7), a trisubstituted olefin (δH 6.65; δC 134.2, 151.9), two methyls (δH 1.72, 1.16; δC 14.5, 20.3), four aliphatic methines with one being oxygenated (δH 4.26; δC 67.3), and four methylenes. Analysis of the 1H,1H-COSY and HMBC spectra, in

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• in Scheme 16, diazo species 18 could be generated from simple carbonyls 15 and hydrazine (16). Intermediate hydrazones 17 can be converted into the corresponding diazo compounds by oxidation using a recyclable oxidant based on N-iodo-p-toluenesulfonamide potassium salt. The possibility to regenerate

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• ) and 136.9 (C-8), 127.0 (C-11) and 135.4 (C-12) pointed towards three carbon–carbon double bonds. Together with two carbonyls (at C-2 and C-18) one RDE accountable to a ring remained, and suggested a cembrane-class diterpene. The proton resonances could be unambiguously assigned to those of directly

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• activation is accomplished through a C–H hydrogen bond with cyclic ester carbonyls. The following study by the Bibal group described the use of catalysts L11 as hydrogen bond donors for the activation of epoxides toward ring-opening aminolysis with amines (Scheme 6) [54]. Significant rate enhancement was

• -workers have re-evaluated the molecular iodine-catalyzed conjugate addition to α,β-unsaturated carbonyls or nitrostyrenes (Scheme 14) [80]. Based on their computational studies, they proposed that iodine activates the enone moiety by forming a halogen bond with the carbonyl and thus forming a more

Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis

• Florin Albota,
• Mino R. Caira,
• Constantin Draghici,
• Florea Dumitrascu and
• Denisa E. Dumitrescu

Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245

• proposed structures for the hybrid heterocycles 12. The signals for the endocyclic and exocyclic CO groups of the sydnone moiety are strongly deshielded and the chemical shifts are very close, appearing in the range of 165.5–166.1 ppm, whereas the carbonyls of the ester groups are shielded by 2–3 ppm. Both

An effective one-pot access to polynuclear dispiroheterocyclic structures comprising pyrrolidinyloxindole and imidazothiazolotriazine moieties via a 1,3-dipolar cycloaddition strategy

• Alexei N. Izmest’ev,
• Galina A. Gazieva,
• Natalya V. Sigay,
• Sergei A. Serkov,
• Valentina A. Karnoukhova,
• Vadim V. Kachala,
• Alexander S. Shashkov,
• Igor E. Zanin,
• Angelina N. Kravchenko and
• Nina N. Makhova

Beilstein J. Org. Chem. 2016, 12, 2240–2249, doi:10.3762/bjoc.12.216

• , because the corresponding endo-transition state would require more energy of activation, as it would result in an electrostatic repulsion between the cis carbonyls thus increasing the free energy of activation [46][47]. As expected, the azomethine ylide adds at the double bond of 1a–c from that side in

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• example epothilone A (119) and oleandomycin (120) (Figure 4) [123][124][125]. Epoxides result from oxidation of olefins by oxidoreductases, mostly cytochrome P450 monooxygenases or FMOs. Alternative mechanisms, such as reactions between carbenes and carbonyls (analogous to the synthetic Corey–Chaykovsky

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• imines, carbonyls or allene homologs. The resulting homologated nucleophile 8 may then be trapped in an intramolecular fashion by a π-allyl complex, which may concomitantly form from 6 through activation of the homoallylic functionality with a suitable transition metal catalyst. According to this concept

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• proline and its derivatives [31]. Recently, Hoveyda and co-workers designed a novel amino acid amide catalyst (cat. 4) for the asymmetric addition of unsaturated organoboranes to carbonyls and imines, producing the corresponding enantiomerically pure alcohols and amines in excellent yields [32]. As shown

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• ; enantioselectivity; iminium ion; oxocarbenium ion; Introduction Nitrogen and oxygen heterocycles with α-stereogenic centers represent important classes of biologicially active compounds [1][2][3][4][5][6][7]. Enantioselective addition of chiral nucleophiles to imines, iminium ions, carbonyls, or oxocarbenium ions

Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• 3.55–3.58 ppm corresponding to H1, while gCOSY was consistent with the presence of a vinyl substituent group. HSQC spectral evidence supported three CH2 groups, while the 13C NMR spectrum confirmed the presence of two free carbonyls with signals at 197.9 and 201.0 ppm. From the HMBC spectrum, a strong

Copper-catalyzed cascade reactions of α,β-unsaturated esters with keto esters

• Zhengning Li,
• Chongnian Wang and
• Zengchang Li

Beilstein J. Org. Chem. 2015, 11, 213–218, doi:10.3762/bjoc.11.23

• mainly based on the lactonization of γ-hydroxy esters, which were obtained through either addition of substituted succinate-derived enolates to carbonyls [3][4][5][6][7], or direct reduction of the corresponding γ-keto esters [8]. Usually they were carried out under acidic or basic conditions, which are

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids

• Zhiqiang Duan,
• Jianlin Han,
• Ping Qian,
• Zirui Zhang,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 969–974, doi:10.3762/bjoc.10.95

• and aliphatic α-keto esters. The possible mechanism is rationalized. Keywords: enantioselective synthesis; hydroxy esters; scandium; Introduction The catalytic enantioselective construction of tertiary carbon centres is a major challenge in organic chemistry. The nucleophilic attack of carbonyls

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• -induced dehydrocyanation of compounds 6 does not produce appreciable yields of pyrroles 7 since the abstraction of the most acidic proton leads to a stable anion reluctant to undergo α-elimination of cyanide. Instead, the anions 8 can be added in vinylogous fashion to α,β-unsaturated carbonyls producing

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• density from the reaction center toward nitrogen. In cases where syn-selectivity is observed, the Cram’s chelation control model provides an explanation [56][57]. Chelating metal coordinates between the two carbonyls (the aldehyde and the carbamate), thus forcing the nucleophile to attack from the si-side

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

• James C. Anderson,
• Andreas S. Kalogirou,
• Michael J. Porter and
• Graham J. Tizzard

Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200

• ]. They have been used to synthesise many nitrogen-containing functional groups including α-amino carbonyls [2][3], peptidomimetics [4], natural products [5][6][7][8][9][10] and many heterocyclic small molecules [11][12][13][14][15][16][17][18][19][20][21][22][23][24] of importance to drug discovery

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• Brønsted or Lewis acid, or by conversion to an activated intermediate such as a haloacetal [1]. Perrhenates, best known as catalysts for large-scale alkene metathesis [2] and isomerization of allylic alcohols [3][4][5][6][7][8][9][10], have been shown to promote condensation of carbonyls with hydrogen

Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways

• Eietsu Hasegawa,
• Minami Tateyama,
• Ryosuke Nagumo,
• Eiji Tayama and
• Hajime Iwamoto

Beilstein J. Org. Chem. 2013, 9, 1397–1406, doi:10.3762/bjoc.9.156

• interconverting 9 and 10 through 8 [22][23][24][25][26][27][28][29][30] might occur (see below). A mechanism on the fragmentation of initially formed metal–organic complexes, giving β-ketoalkyl radicals [40], cyclopropoxy radicals [25][28][48][49][50], or β-metalated carbonyls [39], is still controversial [35][36

Lanostane- and cycloartane-type triterpenoids from Abies balsamea oleoresin

• Serge Lavoie,
• Charles Gauthier,
• Jean Legault,
• Sylvain Mercier,
• Vakhtang Mshvildadze and
• André Pichette

Beilstein J. Org. Chem. 2013, 9, 1333–1339, doi:10.3762/bjoc.9.150

• quaternary carbons, including those at δC 170.8 and 207.6 representing carboxylic and ketone carbonyls, respectively (Table 1). The 1H NMR spectrum showed two doublets at δH 0.35 (J = 3.9 Hz) and 0.52 (J = 3.9 Hz) characteristic of a cyclopropane ring (Table 2), suggesting that 4 is a member of the