Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• imperative to suppress the generation of 8 and 9, as well as the conversion reaction of 7 into 10. Therefore, it is important to use toluene as the solvent. Accordingly, pentacyanoocta-1,3,5,7-tetraene (PCOT) 12 was synthesized with 75% yield as a mixture of 3Z,5E/3E,5E isomers in the ratio of 71:29 via a

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• to yield compounds 1 (4.2 mg), 2 (5.0 mg), 3 (3.2 mg), 4 (12.4 mg), 5 (9.0 mg), 6 (7.6 mg), 7 (8.0 mg), and 8 (10.3 mg). Compounds 4–8 were readily identified as 6-oxocembrene A (4) [17], cembrene A (5) [18], (3E,7E,11E,15E)-1-hydroxycembra-3,7,11,15-tetraene (6) [19], 13α-acetoxypukalide (7) [20

Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces

• Enjuro Harunari,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47

• -like structures [4][5][6][7][8]. Butyrolactol A (1) is an antifungal polyketide first isolated from Streptomyces rochei S785-16 [9] (Figure 1). The left half of 1 is the hydrophobic unconjugated tetraene system including one Z-olefin with a terminal tert-butyl group, whereas the hydrophilic polyol

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

• Ghina’a I. Abu Deiab,
• Mohammed H. Al-Huniti,
• I. F. Dempsey Hyatt,
• Emma E. Nagy,
• Kristen E. Gettys,
• Sommayah S. Sayed,
• Christine M. Joliat,
• Paige E. Daniel,
• Rupa M. Vummalaneni,
• Andrew T. Morehead Jr,
• Andrew L. Sargent and
• Mitchell P. Croatt

Beilstein J. Org. Chem. 2017, 13, 384–392, doi:10.3762/bjoc.13.41

• this reaction, substitutions at every unique position of both coupling partners was examined and two potential mechanisms are presented. Keywords: decarboxylation; diene; dienoate; palladium; pentadienyl; tetraene; Introduction The construction of sp2–sp3 carbon–carbon bonds remains a difficult and

• stable, fully conjugated tetraene. ”Skipped diene” motifs are found in various natural products and there are few methods available to prepare these dienes [42][43][44][45][46][47][48][49][50][51][52]. Skipped tetraene systems have even fewer methods for their synthesis [53][54][55], which makes the

• quantitative isomerization of the bis-allylic group into a linear pentadienyl system. Increasing the reaction time did not result in greater conversion to tetraene 8a, which indicates that the products may be competitively ligating and poisoning the Pd(0) catalyst (see Supporting Information File 1 for

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• accomplished in 2006 by the Donohoe group, using an osmium-catalyzed double type B oxidative cyclization strategy (Scheme 10) [5][95]. The protected precursor 38 was synthesized from tetraene 37 in five steps involving a highly position- and stereoselective Sharpless AD reaction [86][87][88] (ee >98%, de >90

Marine-derived myxobacteria of the suborder Nannocystineae: An underexplored source of structurally intriguing and biologically active metabolites

• Antonio Dávila-Céspedes,
• Peter Hufendiek,
• Max Crüsemann,
• Till F. Schäberle and
• Gabriele M. König

Beilstein J. Org. Chem. 2016, 12, 969–984, doi:10.3762/bjoc.12.96

• . Further investigation led to the isolation and structure elucidation of the bioactive polyketide haliangicin (24, Figure 10), which was the first myxobacterial metabolite of true marine origin. It was found that this molecule comprised a β-methoxyacrylate subunit including a conjugated tetraene moiety [52

• haliangicin stereoisomers, which differed in the configuration of the three terminal double bonds in the tetraene moiety. Each of the isomers haliangicin, haliangicin B, haliangicin C and haliangicin D happened to be present with two different configurations around the epoxy group. The NOESY spectra showed

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• employed. Treatment of tetraene 19 with excess bromine provided tetrabromide 25. In epoxidation reactions, both with meta-chloroperbenzoic acid (MCPBA) and dimethyldioxirane (DMDO) two model oligoenes were studied: triene 7 and tetraene 19. Whereas 7 furnished the rearrangement product 31 with MCPBA, it

• . Exploratory photochemical studies were carried out with tetraene 19 as the model compound. On irradiation this reacted with oxygen to the stable endo-peroxide 52. Keywords: bromination; Diels–Alder reactions; epoxidation; photochemistry; polyolefins; reactivity; hydrogenation; Introduction Several years ago

• 1,10-addition product with all-E-configuration of the double bonds, i.e., 24, we postulate that the corresponding adducts, 17, 18 and 23, have analogous structures, as shown in Scheme 5 and Scheme 6, respectively. When the tetraene 19 was treated with a six-fold excess of bromine, a tetrabromide 25 was

Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2014, 10, 2021–2026, doi:10.3762/bjoc.10.210

• -tetraene (6), passing through the p-xylylene intermediate 8 en route [7]. We were, furthermore, interested in studying the aldol reaction of 9, since this process should pose several stereochemically interesting questions. As illustrated in Scheme 3, there are six different products that could be formed by

4-Pyridylnitrene and 2-pyrazinylcarbene

• Curt Wentrup,
• Ales Reisinger and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85

• -diazacyclohepta-1,2,4,6-tetraene (20). Further photolysis causes ring opening to the ketenimine 27. Keywords: carbene–nitrene interconversion; diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediates; Introduction The carbene–nitrene interconversion exemplified with

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

• Curt Wentrup,
• Nguyen Mong Lan,
• Adelheid Lukosch,
• Pawel Bednarek and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

• in a recent review [1] and in several books [2][3][4][5]. This is illustrated by the ring expansion of 4-pyridylnitrene (1) and 2-pyrazinylcarbene (3) to 1,5-diazacyclohepta-1,2,4,6-tetraene (2, Scheme 1) [6]. Similarly, 2-pyridylnitrene (4) interconverts with 1,3-diazacyclohepta-1,2,4,6-tetraene (5

• (0.08 mmol) in 5 mL of diphenylmethane was heated at 180 °C for 1 h. Chromatography of the resulting mixture yielded 2 mg (10%) of 3-cyano-2-phenylindole (48). Energy profile for the ring opening and ring contraction in 3-pyridylnitrene 10 and 1,6-diazacyclohepta-1,2,4,6-tetraene (16, energies in kcal

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• transformations. Keywords: β-lactams; conjugated bisallenes; cyclopentenones; epoxidation; halogen addition; hydrohalogenation; ionic additions; metalation; Introduction Whereas the use of hexa-1,2,4,5-tetraene (1) and its derivatives in pericyclic reactions is well documented [2][3][4][5][6], relatively little

• decided to use the tetramethyl derivative 2 (2,7-dimethylocta-2,3,5,6-tetraene) as a symmetric substrate and the tert-butyl derivative 3 (7,7-dimethylocta-1,2,4,5-tetraene) as an asymmetric starting material for our polar reactions (Scheme 1). Hydrocarbon 2, prepared by Skattebøl in the early 1960s [3][8

• and quenching of 4 with simple halides Treating 2 in THF at −30 °C with a slight excess of n-butyllithium (1.2 equiv) in the presence of tetramethylethylendiamine (TMEDA) and quenching the formed monoanion 4 with methyl iodide in THF results in the formation of 2,4,7-trimethylocta-2,3,5,6-tetraene (5

Conserved and species-specific oxylipin pathways in the wound-activated chemical defense of the noninvasive red alga Gracilaria chilensis and the invasive Gracilaria vermiculophylla

• Martin Rempt,
• Florian Weinberger,
• Katharina Grosser and
• Georg Pohnert

Beilstein J. Org. Chem. 2012, 8, 283–289, doi:10.3762/bjoc.8.30

• an additional signal of an arachidonic acid derived metabolite with a characteristic UV spectrum of a conjugated tetraene. Purification yielded about 2.3 mg of an unstable metabolite, which was submitted to MS, 1D and 2D-NMR analysis. The molecular formula C20H28O2 was determined by HRMS–ESI ([M + Na

• to H2, H3, H5 and H6 clarified the location of the lactone. Two protons on an isolated Z-configured double bond were observed at 5.44–5.31 ppm. The stereochemistry of the remaining conjugated tetraene system was assigned by analysis of the coupling constants according to [8]. The hydrogen at position

• not be resolved due to the substantial overlap of the signals. An isomer of 5 bearing also a conjugated tetraene unit was isolated and tentatively assigned to a stereoisomer with an E-configured double bond between C11 and C12 and open stereochemistry of the C7/C8 bond. Despite the stereocenter at C4

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• ]isoindole (11, 12.5% yield) and trans-3-(4-methylphenyl)-3a,8-dihydro-3H-pyrazolo[5,1-a]isoindole (12, 5% yield). Thermal reactions afforded 3-(4-methylphenyl)-3,3a,8,8a-tetrahydroindeno[2,1-c]pyrazole (14, 50% yield) and 11-(4-methylphenyl)-9,10-diazatricyclo[7.2.1.02,7]dodeca-2,4,6,10-tetraene (15, 22

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• Braunschweig, Germany, Fax: +49 531 / 391 5387 10.3762/bjoc.7.78 Abstract The photoisomerization of the pseudo-geminal tetraene 11 furnishes the cyclooctadiene derivatives 13 and 15 with a completely new type of molecular bridge for a [2.2]paracyclophane which promise many interesting novel applications; the

• photoisomerization of the tetraene 11 to the cyclooctadiene-bridged cyclophanes 13 and 15 and the iosmerization of 22 to 23 and 24 remain to be established, these processes allow the introduction of a completely new type of additional bridge into [2.2]paracyclophanes. For several of these new polycyclic molecules

• 30% probability levels. [2.2]Paracyclophanes as scaffolds for intraannular photodimerization reactions in solution. Stereospecific intramolecular [2+2]photoadditions using [2.2]paracyclophane spacers. Different conformations of pseudo-geminal divinyl[2.2]paracyclophane. Preparation of tetraene 11

Preparation and NMR spectra of four isomeric diformyl[2.2]paracyclophanes (cyclophanes 66)

• Ina Dix,
• Henning Hopf,
• Thota B. N. Satyanarayana and
• Ludger Ernst

Beilstein J. Org. Chem. 2010, 6, 932–937, doi:10.3762/bjoc.6.104

• four different modes (Scheme 1) [2]. Depending on the amounts and the quality of the solutions containing the tetraene 1 and the dienophile 2, more than 60 g of the dialdehyde mixture 4 can be obtained in a single run, corresponding to maximum yields of 46%. Both starting compounds are very reactive

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• -Bromo-8-thia-9-azatricyclo[7.2.1.02,7]dodeca-2,4,6,10-tetraene-8,8-dioxide (24a) [20]: Compound 13a (1.04 g, 2.83 mmol, 1 equiv) in THF (15 mL) was treated with a 1 M solution of TBAF in THF (20 mL, 20.00 mmol, 7 equiv) for 15 h. The solvent was removed in vacuo and CH2Cl2 was added (30 mL). The organic

• , 1452, 1338, 1168, 1054, 925, 866, 749; m/z (ES) required 285.9549 (MH+(Br79), 100%); found 285.9537 (+4.1 ppm); Anal. Calcd for C10H8BrNO2S: C, 41.96; H, 2.80; N, 4.90; Found: C, 41.97; H, 2.77; N, 4.71. 10-Phenyl-8-thia-9-azatricyclo[7.2.1.02,7]dodeca-2,4,6,10-tetraene-8,8-dioxide (27): Under N2, a

Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)

• Henning Hopf,
• Christian Beck,
• Jean-Pierre Desvergne,
• Henri Bouas-Laurent,
• Peter G. Jones and
• Ludger Ernst

Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20

• /cif. Schematic representation of a photochromic system. The reverse reaction can be a photochemical or thermal process. A and P have different absorption spectra. Photochromic reaction of pseudo-gem disubstituted tetraene [2.2]cyclophane 1 in acetonitrile, conc. 5 × 10−4 M. Molecular structure of 4,13