Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• nucleophile. Mild reaction conditions allow the formation of diversely functionalized fused bicyclic lactones. The products participate in facially selective additions from the convex surface, leading to allylic alcohol derivatives. Keywords: conjugate addition; cyclohexadienones; dearomatization

• ] nucleophiles using bifunctional cinchona alkaloid catalysts. The Sasai and Enders groups used a phosphinothiourea to enable a Rauhut–Currier reaction to form bicyclic enones [16]. The Tian and Lin group used alkyne-tethered cyclohexadienones in an arylrhodation/conjugate addition sequence that

• developed an acyl anion addition promoted by N-heterocyclic carbenes (NHC) that furnished bicyclic furanones via Stetter addition [21]; later, the You group developed an extension of this theme using the same catalytic manifold [22]. More recently, the Corey group has enabled the enantioselective conjugate

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• (R = Me, CF3, Ph, ClCH2) in good yields was presented, although they were transformed further without isolation [14]. An old observation with a long-lasting impact was made by M. Busch who studied the reaction of formic acid with triphenylaminoguanidine: the originally assumed bicyclic constitution

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• monodecyanated products 69a,b. Bicyclic lactones 70a,b are then obtained in 3 steps in 41% and 51% yields, respectively, from 69a,b. Later Curran’s group discovered that NHC-boryl radicals, generated from NHC-boranes (N-heterocyclic carbene boranes), abstracted the cyano group from various organic nitriles and

• [106]. Synthesis of bicyclic lactones [119][120]. Reductive decyanation of malononitriles and cyanoacetates using NHC-boryl radicals (9 examples). For 74 and 75, isolated or NMR yields are given from 71 [121]. Proposed mechanism for the reduction by NHC-boryl radicals. The other possible pathway

Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

• Cira Mollings Puentes and
• Thomas J. Wenzel

Beilstein J. Org. Chem. 2017, 13, 43–53, doi:10.3762/bjoc.13.6

• , 18 and 20 where one of the P-CDs causes the largest enantiomeric differentiation. Substrates 21–26 contain bicyclic indoline, indane and indole rings. The P-CDs were only effective at causing enantiomeric differentiation in the 1H NMR spectra of a few resonances of 21, 24 and 26 (Table 4). With only

Biochemical and structural characterisation of the second oxidative crosslinking step during the biosynthesis of the glycopeptide antibiotic A47934

• Veronika Ulrich,
• Clara Brieke and
• Max J. Cryle

Beilstein J. Org. Chem. 2016, 12, 2849–2864, doi:10.3762/bjoc.12.284

• -Hpg7 peptide as well as the mono- and bicyclic products based on P450-catalysed turnover have been analysed in earlier studies [13][16][17]. Prior to the activity assay the substrate was loaded onto the A47934 PCP-X di-domain construct exhibiting maltose binding protein as N-terminal fusion partner

• previous in vitro and in vivo experiments that indicate that the presence of the C-O-D ring is a prerequisite for the activity of subsequent P450 enzymes, such as StaF (Figure 4, Table 1 entry 1) [13][16][22][27][28][29][32]. Both mono- and bicyclic peptide products could be detected in samples with StaH

• included in the turnover assay: given that we have demonstrated that StaH is capable of producing a C-O-D ring containing peptide from a linear precursor [12] and the lack of StaF activity against linear peptide substrates, we conclude that the formation of the bicyclic peptide is due to the activity of

New syntheses of (±)-tashiromine and (±)-epitashiromine via enaminone intermediates

• Darren L. Riley,
• Joseph P. Michael and
• Charles B. de Koning

Beilstein J. Org. Chem. 2016, 12, 2609–2613, doi:10.3762/bjoc.12.256

• of the naturally occurring indolizidine alkaloid (±)-tashiromine and its unnatural epimer (±)-epitashiromine are demonstrated through the use of enaminone chemistry. The impact of various electron-withdrawing substituents at the C-8 position of the indolizidine core on the preparation of the bicyclic

• piperidine or a pyrrolidine-based precursor, with few reports of alternative approaches. The approach adopted by our research group to the synthesis of these and related bicyclic alkaloids takes advantage of enaminone chemistry [10][11][12][13][14][15][16][17][18][19]. Our interest in the enaminone manifold

• electrophilic substituents are attached to the nitrogen, alkylating or acylating cyclisation onto the enamine carbon site leads to the formation of bicyclic systems with nitrogen located at the bridgehead. Our approach to the synthesis of indolizidines is thus unusual in that it entails the formation of the C-7

Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

• Michał Malik and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2016, 12, 2602–2608, doi:10.3762/bjoc.12.255

• well-known and recognizable group of carbasugars. The synthesis of these monocyclic compounds (such as 1 and 2, Figure 1) and evaluation of their biological properties remain a challenging and vital research area [8][9][10][11]. On the other hand, bicyclic analogs of cyclitols are not as well

• -documented as their monocylic counterparts. However, polyhydroxylated derivatives of decalin and hydrindane are interesting synthetic targets, since they can be regarded as conformationally locked carbasugars (3 and 4, Figure 1) [12][13][14][15]. Indeed, some of the bicyclic carbasugars were proven to

• possess strong and selective anti-glycosidase activity [16][17][18]. The polyoxygenated bicyclic motif is also found in some members of the nargenicin antibiotics family [19][20][21]. In our group, we have already proposed an approach to the synthesis of polyoxygenated bicyclic systems such as cis

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• intrinsic greenness potential based on threshold atom economy and reaction yield values. The application of this methodology was extended to several kinds of monocyclic and fused aromatic heterocyclic rings. We will report on the application of the integer partition algorithm to fused bicyclic and bridged

• bicyclic ring frameworks elsewhere. Possible two-component couplings for various monocyclic rings frequently encountered in organic molecules. Synthesis bonds are shown as bolded bonds. Possible three-component couplings for various monocyclic rings frequently encountered in organic molecules. Synthesis

Et₃B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

• Ahlem Abidi,
• Yosra Oueslati and
• Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

• interesting synthesis of bicyclic dienones in a one-pot process involving the reaction of 2-(acetoxymethyl)cyclohex-2-enone with 1,3-dicarbonyl compounds using K2CO3 as a weak base. Later, Chamakh and Amri [38] have described a one-pot synthesis of (E)-4-alkylidene-2-cyclohexen-1-ones through a cross coupling

Combined experimental and theoretical studies of regio- and stereoselectivity in reactions of β-isoxazolyl- and β-imidazolyl enamines with nitrile oxides

• Ilya V. Efimov,
• Marsel Z. Shafikov,
• Nikolai A. Beliaev,
• Natalia N. Volkova,
• Tetyana V. Beryozkina,
• Wim Dehaen,
• Zhijin Fan,
• Viktoria V. Grishko,
• Gert Lubec,
• Pavel A. Slepukhin and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2016, 12, 2390–2401, doi:10.3762/bjoc.12.233

• crystalline compounds, ligands for asymmetric synthesis, and they are also convenient reagents in organic synthesis [1]. Although bicyclic assemblies of azoles exhibit interesting chemical properties and biological activities [1][7][8][9][10][11] isoxazoles conjugated to other azole rings are poorly presented

Methylenelactide: vinyl polymerization and spatial reactivity effects

• Judita Britner and
• Helmut Ritter

Beilstein J. Org. Chem. 2016, 12, 2378–2389, doi:10.3762/bjoc.12.232

• also shows additional postulated radical reactions including the formation of a bicyclic lactide radical to initiate the main polymerization. Since the spontaneous homolytically C–H cleavage may represent the first step in the reaction cascade, theoretical calculations on a DFT level were conducted

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• with aldehydes or ketones yielding bicyclic structures [25][26][27], or by the reduction of the corresponding dihydroquinazolinones [15][16][17] (Scheme 1). The aminal templates obtained can be used as starting materials for the synthesis of a broad spectrum of diverse structures. Oxidation reactions

Isosorbide and dimethyl carbonate: a green match

• Fabio Aricò and
• Pietro Tundo

Beilstein J. Org. Chem. 2016, 12, 2256–2266, doi:10.3762/bjoc.12.218

• presence of the nitrogen bicyclic base DBU. It has been, in fact, reported that organic carbonates are activated by DBU via formation of an N-alkoxycarbonyl DBU derivative [67][68][69][70][71]. However, in this case study, DBU most probably promotes the formation of the methoxycarbonyl reaction

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• towards highly electrophilic p-nitrophenyl carbonate derivatives with ring opening of the bicyclic ring to form corresponding substituted ε-caprolactam and γ-lactam derived carbamates. This simple method presents a unified strategy to synthesize structurally diverse ε-caprolactam and γ-lactam compounds

• synthetically useful and strong neutral bases. Besides, DBU and DBN catalyze various organic reactions such as dehydrohalogenations [1], carbonylations [2], amidations [3] and Baylis–Hillman reactions [4]. These bicyclic amidines have been thought to be non-nucleophilic bases, but meanwhile numerous examples

• nucleophiles towards halo derivatives of main group elements where the DBU and DBN bicyclic rings remained unaffected [10][11]. Later in 1994, Lammers et al. observed the nucleophilicity of amidine bases with 4-halo-3,5-dimethyl-1-nitro-1H-pyrazole and their subsequent ring opening leading to the lactam

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• and experimental studies on the hetero-Diels–Alder reaction of the chiral 1-phosphono-1,3-butadiene 31 with nitroso dienophiles 32 (Scheme 6) [87]. The authors studied the reactivity of chiral 1-phosphonodienes modified with the bicyclic (R,R)-1,3,2-dioxaphospholane 31a or (R,R)-1,3,2

• -diene (120) with the acylnitroso dienophile 119 (Scheme 24) [10]. The reaction proceeded in 81% overall yield with a major cycloadduct 121 and minor diastereomer 122, with 98% de. The absolute configuration of the major cycloadduct was confirmed by an independent synthesis from the known bicyclic (1R,4S

• ][119]. Their utility was demonstrated by the synthesis of (+)-mannostatin A (138, Scheme 26) [120]. Here, the symmetric cycloaddition of the acylnitroso compound 117, derived from (R)-mandelic acid, to 1-(methylthio)cyclopenta-2,4-diene (135) predominantly afforded the bicyclic adduct 137 (in a ratio

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• natural products, have been used as chiral phase-transfer catalysts [12][13]. Bicyclic guanidines with five-membered rings are also known from the alkaloid isoalchornein [14][15]. In subsequent years, synthetic compounds (6–9) of this structural type have been developed as chiral Brønsted bases [16][17

Mechanistic investigations on six bacterial terpene cyclases

• Patrick Rabe,
• Thomas Schmitz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1839–1850, doi:10.3762/bjoc.12.173

• bicyclic structure (Table 1). The signals of the hydrogens attached to each carbon were assigned by HSQC spectroscopy, while the 1H,1H-COSY revealed a contiguous spin system C3-2-1-6(-5)-7(-11(-13)-12)-8-9 and two separate methyl groups attached to the quarternary olefinic carbons (Figure 2a). The HMBC

Three-component synthesis of highly functionalized aziridines containing a peptide side chain and their one-step transformation into β-functionalized α-ketoamides

• Lena Huck,
• Juan F. González,
• Elena de la Cuesta and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2016, 12, 1772–1777, doi:10.3762/bjoc.12.166

• involve the base-promoted formation of the bicyclic aziridine 4, where nitrogen conjugation to the adjacent carbonyl would be geometrically constrained. The associated increase in reactivity for this carbonyl would explain the complete selectivity of the diketopiperazine ring opening, with concomitant

Synthesis of the C8’-epimeric thymine pyranosyl amino acid core of amipurimycin

• Pramod R. Markad,
• Navanath Kumbhar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2016, 12, 1765–1771, doi:10.3762/bjoc.12.165

• -dioxabicyclo[3.2.1]octane A could be glycosylated stereoselectively with the requisite nucleobase to give β-nucleoside pyranosyl skeleton 2. The bridged bicyclic system A was visualized from the azido diol B. Thus, hydrolysis of the 1,2-acetonide functionality in B will lead to in situ generation of

• attack of the secondary hydroxy group to the oxocarbenium ion Y led to a stable six-membered pyranose ring compound thus shifting the equilibrium in favour of bridged bicyclic system 12/13. In order to validate the configurational assignments at the newly generated stereocenters, the coupling constants

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• hydroperoxides, bicyclic hydroperoxides and о-hydroxyphenyl alkyl ketones. Instead, cyclic 2-methylchroman-2-yl hydroperoxide 188, geminal bishydroperoxides 190, and condensation products of peroxides such as 191 were isolated (Scheme 56). The reaction mechanism presumably involves the following steps: the

• transformation into geminal dihydroperoxide 190 was observed (Table 13). The formation of geminal dihydroperoxides 195 was also observed in the acid-catalyzed reaction of bicyclic secondary alcohols 192 with hydrogen peroxide. This reaction starts with the formation of bicyclic hydroperoxides 193 followed by the

• treatment of unsubstituted bicyclic endoperoxides 229 by bases affords 4-hydroxyenones 230 [344] which are useful precursors in asymmetric organic syntheses. Alternative synthetic methods towards this class of compounds normally require a metal-catalyzed or biocatalyzed oxidation of diols 231 in an

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• rates of hydrolysis for six-membered 15 and 8 could be explained with the kinetic anomeric effect. Consistent with this, the X-ray crystal structure of an analogous yet conformationally constrained bicyclic orthoester possesses an unusually elongated axial C─O bond (Figure 2a), which undergoes

Discovery of an inhibitor of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells

• Bernardas Morkunas,
• Balint Gal,
• Warren R. J. D. Galloway,
• James T. Hodgkinson,
• Brett M. Ibbeson,
• Yaw Sing Tan,
• Martin Welch and
• David R. Spring

Beilstein J. Org. Chem. 2016, 12, 1428–1433, doi:10.3762/bjoc.12.137

• protected amide intermediate is known to form; presumably upon treatment with acid the liberated ketone group is then attacked intramolecularly by the electron-rich aromatic ring system to form the bicyclic ring system. Other synthetic routes to such 4-alkylquinolin-2(1H)-one analogues involve

• accurate reproduction of the crystallographic binding mode of OdDHL. Conversely, the best score for 4 (−9.7 kcal/mol) was obtained when it was docked into the flexible conformation of LasR LBD without water. In order to accommodate the bicyclic moiety of 4, Arg61, which points into the OdDHL binding pocket

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• important consequence of this motion is that the p AO on the opposite side of the ring in 34 has the correct phase to generate a C–C σ bond and this collapses to bicyclic 32. Our calculations find that C8F8–Pt(dpe) will be caught in the deep potential energy well of the tricyclic isomer, 32. Hughes and co

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• desired precursor compounds A (1–6) were obtained in reasonable overall efficacies (for details see Supporting Information File 1). We start our report with the palladium-catalyzed reactions of simple alkyl ketones 1 and 2 leading to bicyclic products and then continue with the transformations of cyclic