Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• triggered by thermal activation, photoirradiation and electron exchange as a powerful synthetic strategy to prepare a variety of π-CPCs. Review Contraction of 7-membered rings: chalcogen extrusion from heteropines The family of chalcogen heteropines, i.e., cycloheptatriene analogues incorporating one group

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• tropones and benzotropones [79]. The reaction of 4,5-benzotropone (11) and 8-oxoheptafulvene (85), prepared in situ via the reaction of cycloheptatriene-7-carboxylic acid chloride (84) with NEt3, afforded 3,4-benzoheptafulvalene 86 in 50% yield as fairly stable deep brown crystals (Scheme 15). The

• -triazoline-3,5-dione (158) gave the cycloadducts 159 and 160 via the cycloheptatriene form. However, usually the norcaradiene type product 161 observed with cycloheptatrienes was not formed (Scheme 27). 3. Chemistry of 2,3-benzotropone (12) 3.1. Synthesis of 2,3-benzotropone (12) Several procedures relating

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

• was still obtained with satisfying de values of 82% for the reaction with cyclohexadiene and 84% with cycloheptatriene, respectively [123]. Dienophile 140b was also reacted successfully with the acyclic dienes 1,4-dimethyl-1,3-butadiene and the ethyl ester of 2,4-hexenoic acid giving the products with

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

• Zakir Hussain,
• Henning Hopf,
• Khurshid Ayub and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

• two isomers (ratio 3:1), which were later separated through reversed-phase HPLC (MeOH/H2O 3:1) and characterized as derivatives 9 and 10 (Scheme 3). The cycloheptatriene unit of 9 adopts, in sterically relaxed systems, a boat-like conformation, whereas its planar form represents the transition state

• of the thermal boat-inversion process. Additionally, since 8 and 9 possess a center of chirality at C(2), there are two different boat conformations of the cycloheptatriene unit possible, namely those in which C(4) is on the same or on the opposite side with respect to the substituent at C(2). The 1H

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• compound 45 failed to extract any cations. 4.2.3 Transition metals: The tris(diphenylphosphine) derivative 26 prepared by Matt [40] was reacted with [Mo(CO)3(cycloheptatriene)] to give a complex that was determined to be the symmetrically bound Mo(CO)3 complex involving all three of the phosphorus donors

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• -1,3,5-triene into the corresponding bicyclo[4.1.0]hepta-2,4-dienes is reviewed to show the impact of the heteroatom on the stability of both valence isomers. The focus is on the parent systems and their synthetic applications. Keywords: aromaticity; cycloheptatriene; heteroatom; valence isomerization

• biological importance (Scheme 1) [3][4]. The phosphane analogues 9 and 10 received far less attention, with their applicability as a phosphinidene (R–P) precursor being the most notable use [5][6][7][8][9]. Reviewing the influence of the heteroatom on the cycloheptatriene–norcaradiene valence isomerization

• they enable reliable insight into the reaction energies and aromatic features of the parent isomers. In this brief review, only selected examples of substituted heteropines and their syntheses are given. Review Cycloheptatriene valence isomerization Cyclohepta-1,3,5-triene (1), first isolated in 1883

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• -activated alkynes and a cycloheptatriene. These cycloadditions were previously reported in the context of a stoichiometric chromium(0) activation of the triene unit [64]. The use of AuCl3 or PtCl2 rendered the reaction catalytic [65]. The mechanism entails a stepwise exo-cyclization of the cycloheptatriene

• )-catalyzed intermolecular (2 + 2) cycloaddition of alkynes with alkenes [62]. Metal-catalyzed cycloaddition of alkynes tethered to cycloheptatriene [65]. Gold-catalyzed cycloaddition of functionalized ketoenynes: Synthesis of (+)-orientalol F [68]. Gold-catalyzed intermolecular cyclopropanation of enynes

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• vinyl alkynyl cyclopropanes 85 to give arenes 86, 87 and cycloheptatriene 88 derivatives through 5-endo-dig and 6-endo-dig cyclization reactions, respectively, under careful control of the reaction conditions (Scheme 25) [58]. A mechanistic rationale for these transformations is shown in Scheme 26

• cations 90 and 91 by delocalization of the positive charge onto gold. The aromatic intermediate 92 is probably converted, via 93, into 86 and 87 by E1 and SN1 mechanisms, respectively. When secondary esters are employed, 6-endo-dig cyclization occurs to give 94, which forms the cycloheptatriene derivate

Gold-catalyzed naphthalene functionalization

• Pedro J. Pérez,
• M. Mar Díaz-Requejo and
• Iván Rivilla

Beilstein J. Org. Chem. 2011, 7, 653–657, doi:10.3762/bjoc.7.77

• nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either from the formal insertion of the carbene unit into the aromatic C–H bond or from its addition to a double

• stable cycloheptatriene product (Scheme 1) [2]. Nearly one century later, Teyssié and co-workers discovered the potential of dirhodium tetraacetate and related Rh2(L-L)4 compounds as catalysts for the decomposition of diazo compounds and subsequent transfer of the carbene moiety to several saturated and

• unsaturated substrates, including aromatics [3]. Thus, the reaction of ethyl diazoacetate (EDA) with benzene in the presence of such catalysts at room temperature exclusively affords the cycloheptatriene product in quantitative yields. The reaction, always referred to the intermolecular version, was later

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• complexation takes place during oxazolidinone formation, we synthesized the cyclic systems 3 with enantiotopic leaving groups at allylic positions on different olefinic faces, where one face of the olefin can be blocked by the substituents Y (Figure 2). Results and Discussion The cycloheptatriene–norcaradiene

• shift the equilibrium to the norcaradiene 4b side, while electron donating substituents, such as –OR, –NR2 favor the cycloheptatriene 4a structure. It has been shown that singlet oxygen and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) are sufficiently reactive to intervene in the cycloheptatriene

• sensitized photooxygenation of the cycloheptatriene derivative 5a5b at room temperature resulted exclusively in the formation of the norcarene endoperoxide 6 [14][17]. The exact configuration of the endoperoxide 6 was determined by the single crystal X-ray analysis of the bisepoxide formed by the thermolysis

Synthesis of oxa-bridged derivatives from Diels–Alder bis-adducts of butadiene and 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene

• Faiz Ahmed Khan and
• Karuppasamy Parasuraman

Beilstein J. Org. Chem. 2010, 6, No. 64, doi:10.3762/bjoc.6.64

• reactions. We and other groups have demonstrated the utility of cyclic dienes for the synthesis of 2:1 Diels–Alder bis-adducts with 1,2,3,4-tetrahalo-5,5-dimethoxycyclopentadiene 1 [4][5][6][7]. In the case of cyclic dienes (or trienes) such as cyclohexa-1,4-diene and cycloheptatriene, endo-syn-endo