Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• dienophile component in inverse-electron demand Diels–Alder reactions, a series of new dihydroindeno[1,2-c]pyran derivatives was synthesized. Thus, the addition of freshly distilled indene as a diene component to oxadiazinones 1 as the dienophiles [29] under acidic conditions (TFA, TFAA) led to the formation

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• electron-rich diene, which reacts with substituted dihydroisoquinoline 14 and dihydro-β-carboline 15, so that cyclohexanone derivatives 16 and 17 will be produced, respectively (Scheme 8) [19]. Also, a cyclic derivative of 13 was utilized (not shown). This aza-Diels–Alder reaction provides products with

• , the product was obtained in 78–90% yield and 15–92% ee. Finally, β-substituted α,β-unsaturated aldehydes were completely unreactive. In 2012, a proposed inverse electron-demand Diels–Alder reaction was reported by Wang and co-workers, obtaining enantiopure products 33, starting from diene 31 and

• of the nucleophile, making the diene more nucleophilic, and lowers the LUMO of the electrophile, making the dienophile more electrophilic (Scheme 19), thus the catalyst acts via a bifunctional mode. All these interactions are developed in the transition state through hydrogen-bonding, which controls

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• (and simple diene isomers) [87], setting the stage for future studies aimed at elucidating the means by which abietadiene synthase steers its reaction away from rearrangement and at engineering abietadiene synthase so that it selectively forms rearranged products. Take home messages: • PTSBs can occur

Regioselective palladium-catalyzed ring-opening reactions of C1-substituted oxabicyclo[2,2,1]hepta-2,5-diene-2,3-dicarboxylates

• Michael Edmunds,
• Mohammed Abdul Raheem,
• Rebecca Boutin,
• Katrina Tait and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 239–244, doi:10.3762/bjoc.12.25

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• the surface of the support. To shed more light on this, we compared the behaviour of 8-powder and 8-C* in the RCM reaction of diene 9 conducted in ethyl acetate at 50 °C. Complex 8 is partially soluble in this solvent. The split tests, made during RCM reactions, revealed a great difference between the

New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

• Agnieszka Hryniewicka,
• Szymon Suchodolski,
• Agnieszka Wojtkielewicz,
• Jacek W. Morzycki and
• Stanisław Witkowski

Beilstein J. Org. Chem. 2015, 11, 2795–2804, doi:10.3762/bjoc.11.300

• potency of the new catalyst 9 was tested not only in standard, model metathesis reactions but was also examined in more demanding systems, such as conjugated dienes and polyenes (Table 4). The CM reaction between alkene and diene (or polyene) often suffers from low regio- and stereoselectivity control

• . The CM reaction may be accompanied by various self-metathesis processes. Additionally, due to the competitive cleavage of both double bonds of the diene substrate, two different products may be formed in the CM reaction between alkene and diene (Scheme 3). A further complication is a Z/E isomer

• . In all reactions the E-isomer of compound A was formed as a main product (Table 4, entries 1–3). Homodimerisation products of diene and alkene were obtained in very small amounts (<2% and <4% for entry 1 and 2, respectively, Table 4). The SM product of methyl vinyl ketone was not observed (entry 3

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• ) polymerization [15][16], living ionic polymerizations, specifically ring-opening polymerization (ROP) [17], as well as migration insertion polymerization (MIP) [18], acyclic diene metathesis polymerization (ADMET) [19][20] and ring-opening metathesis polymerization (ROMP) [21][22][23][24][25][26][27]. These

• norborn-5-ene-(N,N-dipyrid-2-yl)carbamide with exo,exo-[2-(3-ethoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-en-2-carbonyloxy)ethyl]trimethylammonium iodide to polymer 38, using the Schrock Mo catalyst. By further reaction with [Rh(COD)Cl]2 (COD = cycloocta-1,5-diene), polymer 38 gave the Rh(I)-appended block

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• catalyst [52] selectively converted diene 90 to the bicyclic ring system 91 in 66% yield. For the installation of the exocyclic double bond, bicycle 92 was treated with Martin sulfurane [53]. Subsequent hydrolysis of the acetal functionality and oxidation of the resulting lactol restored the lactone

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• liberated through ligand exchange on the methylidene 2 (Scheme 5). To complete their study, the authors examined the influence of the amines on the GII-catalyzed RCM of diene 13 [45]. In the presence of amines a–c, decomposition was observed and CH3PCy3+Cl− was generated. Interestingly, in the presence of

• -dihydroquinolizinium salts (Scheme 13) [50]. In their synthetic approach towards (R)-(+)-muscopyridine, Fürstner and Leitner have constructed the 13-membered ring macrocycle using a RCM applied to diene 34 [51]. In order to avoid the catalyst deactivation due to the presence of the pyridine moiety, the precursor 34

• it may be suspected that the presence of the two chlorine atoms significantly decreased the basicity of the pyridine (Scheme 21). Tricyclic compound 59 was prepared by a RCM of diene 58 that incorporates a quinoline moiety [61]. In this case, a phenyl group was present at C2 and may be responsible

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• % overall yield and in a diastereomeric ratio of 1:1 (Table 1, entry 9). These results were quite surprising as these catalyst/solvent systems were effective in our previously reported Diels–Alder cycloadditions involving 1a as diene [18][19][20][21]. In particular, under gold catalysis excellent results in

• -vinylindoles 1a–j. Results are shown in Table 2. Table 2, entries 1 and 2 report the best results for the cycloaddition reaction of 1a with 2, obtained during the reaction conditions screening (see Table 1). Quite surprisingly, indole 1b bearing a methyl group at the distal position of the diene system, gives

• good yields and excellent diastereoselectivities. A considerable drop in yield is observed using dienes substituted in position 5 of the indole ring with an EWG or an EDG such as fluorine or methoxy (Table 2, entries 9 and 10). Finally, the indole 1i, unsubstituted at the terminal position of the diene

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• obtained by RRM of 124 using catalyst 1 under ethylene (24) atmosphere. Interestingly, the diene building block 128, produced by employing an enyne-ring rearrangement metathesis (ERRM) sequence, was subjected to a DA reaction in refluxing toluene with various dienophiles such as dimethyl

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

• Jingjing Wang,
• Samuel Z. Y. Ting and
• Joanne E. Harvey

Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197

• reaction with a view to future synthetic ease [50]. Pleasingly, the reaction of aldehyde 8 with alcohol 7c in toluene provided the desired product 5c in a comparable yield (66%) after 5 h. In these reactions, only the desired E,Z-diene isomer was observed. Conclusion In summary, an efficient three

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• o-trifluoroacetamidocinnamaldehyde dimethylhydrazone playing the role of the diene. This medium was refluxed in toluene for 12 h and the product was oxidized with manganese oxide to give two intermediates. The latter were separately subjected to cyclization and deprotection reactions in alkaline

• pyrroloquinone [60]. The halogen presumably increased the electron delocalization in the diene allowing the overlap of molecular orbitals. Synthesis of neoamphimedine (12) Method A: To prepare neoamphimedine, 4-methoxy-2,6-dinitrophenol was methylated with diazomethane and the product was partially reduced to

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• 96% yields, respectively. Interestingly, the more sterically-demanding diene 10 afforded the trisubstituted olefin cyclized product with high 93% isolated yield. Catalyst 4a was also efficient regarding the cyclization of enynes 12 and 14 and the desired diene products were obtained with 89 and 90

Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• ” complexes 1 and Ind-I (Table 2). The diene 6 was poorly converted by mixed PCy3/P(OR)3 complex 1, whereas 94% conversion was obtained with Ind-I (Table 2, entries 1–4). In the case of tri-substituted diene 8, a more challenging substrate compared to 6, pre-catalyst 1 gave 79% conversion while Ind-I

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• noteworthy that this is one of the few examples of this tandem protocol that employs olefins other than ethylene. Experimental General procedure for the tandem protocol. A solution of Hoveyda–Grubbs 2nd generation (5 mol %), diene 2 or 8 (3.0 equiv) and alkyne 1 (0.5 mmol) in dry toluene 0.05 M was heated at

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

• moderate yield. RCM of the diene derived from the dialdehyde 111 afforded the macrocyclic cyclophane 113 as a less strained product (Scheme 16). Sonogashira coupling: Wegner and co-workers [125] have reported the synthesis of cyclophanes 122a–c via Sonogoshira coupling [126] (Scheme 17). To this end, the

• ]. Based on this proposal Shair and co-workers attempted the synthesis of the natural product (−)-longithorone A. Diene 343 and the dienophile 342 were synthesized by several steps and subsequently subjected to the DA sequence to afford the rigid (−)-longithorone A (346, 90%, Scheme 60). Nicolaou and co

• -workers [198] have reported the synthesis of sporolide B (349). The synthesis involves a DA reaction between o-quinone as the diene component and indene derivatives as dienophiles. This total synthesis also involves a

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

• Lebensmittelsicherheit (BVL), Messeweg 11/12, D-38104 Braunschweig, Germany 10.3762/bjoc.11.139 Abstract The chemical behavior of various oligoenes 2 has been studied. The catalytic hydrogenation of diene 3 yielded monoene 4. Triene 7 was hydrogenated to diene 8, monoene 9 and saturated hydrocarbon 10. Bromine addition

• we described [2] a general synthesis of a series of terminally substituted, conjugated polyenes, 2, beginning with the diene and ending with the decatriene (Scheme 1). We also reported the X-ray structures of compounds with n = 1, 2, 3, 4, 5 and 7 and discussed the structural similarities, in

• of the hydrocarbons 2. Results and Discussion Catalytic hydrogenation We started our studies on the reactive behavior of polyolefins 2 with one of the formally simplest alkene reactions: catalytic hydrogenation. When diene 3 was hydrogenated under relatively mild conditions (Pd/C, EtOH, room temp

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• -aromatic alkenes. Addition to non-aromatic alkenes As expected non-aromatic alkenes are less good substrates for the radical addition of amidyl radicals and the yields of addition products of 2a decreased significantly (Table 3). A conjugated diene like cyclooctadiene (Table 3, entry 4) and a terminal

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• situ to the transient diene by reductive elimination using naked iodide [37][38][39] or the iodo-ionic liquid 1-butyl-3-methylimidazolium iodide [40]. After purification by column chromatography on silica gel, we noted that complete aromatization has occurred concomitantly and molecular clip 4 was

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

• Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

• bicyclic dienes can act as useful chiral ligands for rhodium-catalyzed ECA reactions. In Carreira’s report, they examined the effectiveness of their diene ligand on the conjugate addition of an α,β-unsaturated amide (Scheme 15). They were able to obtain the 1,4-addition product both in high yield and

• enantioselectivity. Since the publication of these results, many different types of chiral dienes have been used in rhodium-catalyzed ECA reactions [148][149]. In 2011, Lin and co-workers reported the rhodium–diene-catalyzed asymmetric 1,4-arylation of γ-lactams [150]. Though He and co-workers previously reported a

• 1,4-arylation of γ-lactams, they obtained the product in moderate yields and good enantioselectivities [151]. When Lin and co-workers were developing their 1,4-arylation procedure, they decided to use a chiral diene because the literature had shown that these ligands provide higher reactivities and

Attempts to prepare an all-carbon indigoid system

• Şeref Yildizhan,
• Henning Hopf and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 363–372, doi:10.3762/bjoc.11.42

• direct conjugation, whereby a third such system is excluded from interaction [3]. Typical examples are 2-vinyl-buta-1,3-diene ([3]dendralene, 3-methylene-penta-1,4-diene), benzophenone or urea. Whereas the hydrocarbon parent systems, the [n]dendralenes, have long been a neglected class of oligoenes [4

• not the hoped-for diene 22, but an isomer, the hydrocarbon 23 (Scheme 5). The structure of hydrocarbon 23 was established by the usual spectroscopic data (see experimental section) and also by an X-ray crystal structure determination (Figure 3). The molecule of 23 is planar (mean deviation 0.03 Å) and

• -diene, requires much higher temperatures than those given in Scheme 5, we assume that the metalorganic reagent (or products derived therefrom) play a role in the isomerization. Hydrocarbon 23 is, in fact, a known compound. It has been prepared previously from indene (6) by other routes [25][26], but

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• -azabicyclo[3.2.1]oct-2-ene and/or 5,7-dioxa-1-azabicyclo[4.3.1]deca-3,8-diene-2-one derivatives. According to DFT calculations (B3LYP/6-31+G(d,p)), the cycloaddition can involve two modes of nucleophilic attack of the dihydroazireno[2,1-b]oxazole intermediate on acetyl(methyl)ketene followed by aziridine

• -membered heterocycles [4][5][6][7][8][9][10][11]. The reactions of azirines with acylketenes [12][13], carboxylic acids [14] and amino acids [1] proceed via N–C3 bond cleavage to afford 5,7-dioxa-1-azabicyclo[4.4.1]undeca-3,8-diene derivatives, ketamides, and aminoamides, respectively. On the other hand

• (hereinafter referred to as the [4.3.1] adduct), and 5,7-dioxa-1-azabicyclo[4.4.1]undeca-3,8-diene derivative 8f. The same catalyst and the same reaction and purification conditions were used in further experiments. Analogous reaction of 4-methoxyphenyl-substituted azirine 1f yielded the same set of products

Switching the reaction pathways of electrochemically generated β-haloalkoxysulfonium ions – synthesis of halohydrins and epoxides

• Akihiro Shimizu,
• Ryutaro Hayashi,
• Yosuke Ashikari,
• Toshiki Nokami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2015, 11, 242–248, doi:10.3762/bjoc.11.27

• three-membered ring bromonium ion or iodonium ion. The reaction of 1-X with alkenes followed by the treatment with NaOMe gave the corresponding epoxides as shown in Table 3. Alkenes having an alkoxycarbonyl group gave the corresponding epoxides in moderate yields (Table 3, entries 11–14). Diene 2f

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• electrochemical conversion were not very successful, so that we turned our attention towards indirect electrochemical methods [18][19]. Among these we became interested in the electrochemical generation of reactive cations inducing a transformation of the 1,4-diene moiety. As a starting point we put our interest

• which takes place exclusively at the internal carbon of the double bond of the terminal alkene (C2) and C4 of the 1-aryl-substituted 1,3-diene. The key intermediate A in the reaction mechanism is proposed to be a cobaltacycle which only allows the double bond generated from the 1,3-diene component to

• with aryl-substituted 1,3-dienes 1a–k because the use of allylic alcohol itself led to significant lower yields (up to 30%). Only in case of buta-1,3-diene, 2,3-dimethyl-1,3-butadiene and isoprene allyl alcohol could be used directly without decreasing the yield (Table 1, entries 12–14). The results of