Synthesis of 6-Styrylheptalenes

Song, Jiaojiao; Hansen, Hans‐Jürǵen

doi:10.1002/(sici)1522-2675(19991006)82:10<1690::aid-hlca1690>3.0.co;2-d

Cited by 5 publications

(5 citation statements)

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“…We synthesized the other azulenes on Hafner×s route from 2,6-dimethyl-4-pyrone (Fluka) via the corresponding pyrylium tetrafluoroborates [10] (see also [26] [28]). The thus formed 6-R-4,6-dimethylazulenes were then formylated and reduced with NaBH 4 in CF 3 COOH/CH 2 Cl 2 [29] (see also [8] [30] (2)); 7.65 (dd, J 0 6.8, J m 1.5, HÀC(2',6')); 7.52 ± 7.40 (m, 3 H of Ph); 7.45 (d, 3 J 3.9, HÀC(1,3)); 7.37 (s, HÀC(5,7); 2.99 (s, MeÀC (4,8)). Table 4 and Fig.…”

Section: Experimental Partmentioning

confidence: 99%

“…The torsion angles, defined mainly by the spatial shape and the conjugation within the two sevenmembered rings of the heptalenes, are close together, especially those of the MeOCOsubstituted ring, in full agreement with the observed 3 J(HÀC(2),HÀC(3)) 5.9 Hz for all 4 heptalenes with occupied peri-positions. The bond angle at C(8) of 2d and 2f with the p-substituents is slightly enlarged in comparison with 2a with s-substitution at C (8). The expected conjugation of the p-substituents with the core CC bonds is also indicated by the observed small cisoid V(C(9)ÀC(8)ÀC(1')ÀC(2'')) values.…”

Section: 4mentioning

confidence: 99%

“…[3a] [7] [8]), we were interested in the synthesis of 8-aryl-substituted heptalene-4,5-dicarboxylates, starting with the corresponding 6-aryl-substituted azulenes. Taking into account that azulenes with Me substituents at C(1) and C (4) give always the highest yields of the corresponding heptalene-4,5-dicarboxylates (cf.…”

mentioning

confidence: 99%

“…Path II is controlled by the SHOMO of azulene and gives rise to the tricyclic compounds 13 [4], which are formed irreversibly under the reaction conditions and may further react with ADM [12]. Path III, leading to the cis-configured tricyclic compounds 14, is not available purely thermally, because most azulenes allow no concerted bonding at C(1) and C (8), or at C(3) and C(4), respectively, due to the fact that the HOMO of these azulenes has orbital coefficients at C(4,6,8) that are zero or at least close to zero. Heavily…”

mentioning

confidence: 99%

“…The calculated DDH f 8 values are almost the same for the structures of the a-and b-compounds and related types 8. ) Of course, ADM may already be added to the cyclohexa-1,3-diene system of 27, followed by a prototropic shift in the formed cycloadduct, resulting in the formation of 29.…”

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confidence: 99%

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New Products from the Heptalene-Forming Reaction of Azulenes and Acetylenedicarboxylates in Polar Media

Singh¹,

Linden²,

Abou‐Hadeed³

et al. 2002

HCA

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A number of azulenes 1, in particular those with p-substituents at C(6) such as phenyl, 3,5-dimethylphenyl, and 4-biphenyl, have been reacted with 3 mol-equiv. of dimethyl acetylenedicarboxylate (ADM) in MeCN at 1108 (cf. Scheme 1). Main products had been, in all cases, the corresponding heptalene-4,5-dicarboxylates 2. However, a whole number of side products, mainly rearranged (1 2)-adducts with two molecules of ADM, in amounts of 0.2 ± 9% were also isolated and characterized (cf. Scheme 2). The 2a,8a-dihydro-3,4-ethenoazulene-1,2-dicarboxylates 14, formed by energetically favorable ring closure from the solvent-stabilized zwitterions 15, resulting from bond heterolysis in the primary cycloadducts 12 (cf. Scheme 3), have been mechanistically identified as the pivotal intermediates responsible for the formation of all side product (cf. Schemes 5, 9, 12, and 13). Deuterium-labeling experiments were in agreement with the proposed mechanisms, indicating that sigmatropic [1,5s]-H shifts in 14 (cf. Scheme 6) as well as isoconjugate [1,4s]-H shifts in resonance-stabilized zwitterions of type 21 (cf. Scheme 9) are the crucial steps for side-product formation. It is postulated that a concluding antarafacial 8e-dyotropic rearrangement is responsible for the appearance of the 2,4a-dihydrophenanthrene-tetracarboxylates of type trans-6 (cf. Scheme 9) in the reaction mixtures, which further rearrange thermally by a not fully understood mechanism into the isomeric tetracarboxylates 7 (cf. Schemes 10 and 11). Most surprising is the presence of a small amount (0.3 ± 1%) of the azulene-4,5,7,8-tetracarboxylate 9 in the reaction mixture of azulene 1a and ADM. It is proposed that the formation of 9 is the result of a [1,5s]-C shift in the spiro-linked intermediates 24, which, after prototropic shift and take-up of a third molecule of ADM, disintegrate by a retro-Diels-Alder reaction into 9 and the phthalic diesters 30 (cf. Scheme 12). The UV/VIS spectra of the p-substituted heptalene-4,5-dicarboxylates 2d ± 2f and their double-bond shifted (DBS) forms 2d ± 2f (cf. Table 4 and Figs. 9 ± 12) exhibit in comparison with the heptalene-dicarboxylates 2a and 2'a, carrying a t-Bu group at C(8), only marginal differences, which are mainly found in the relative intensity and position of heptalene bands II and III.

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Section: Experimental Partmentioning

confidence: 99%

Section: 4mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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New Products from the Heptalene-Forming Reaction of Azulenes and Acetylenedicarboxylates in Polar Media

Singh¹,

Linden²,

Abou‐Hadeed³

et al. 2002

HCA

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Addition of Organochromium Reagents to Carbonyl Compounds

Takai

2004

Organic Reactions

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Organochromium compounds can be prepared by two methods: (1) transmetallation from the corresponding organolithium, ‐magnesium, or –zinc compounds with chromium(III) halides, and (2) reduction of organic substrates, such as halides and unsaturated compounds with chromium(II) salts. The second method is usually the one ised because the first method suffers from low solubility of chromium(III) salts in ethereal solvents and from the difficulty of preparing organolithium compounds. Low‐valent chromium species are reducing agents. Reduction of various types of organic halides and compounds having unsaturated hetero‐hetero bonds with the chromium (II) species is discussed. Also described are the transmetallation to organochromium compounds from other organometallics, the nature of the carbon‐chromium bonds, and the X‐ray structure of chromium compounds. Reactions of organochromium reagents with carbonyl compounds and their scope and limitations are described. Included in this discussion are the geminal chromium reagents. Other reagents discussed are the chromium‐nickel compounds and alkylchromium and other organochromium reagents.

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Recent Advances in Phase‐transfer Catalysis

Sasson

Rothenberg

2002

Handbook of Green Chemistry and Technology

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Synthesis of 6-Styrylheptalenes

Cited by 5 publications

References 11 publications

New Products from the Heptalene-Forming Reaction of Azulenes and Acetylenedicarboxylates in Polar Media

New Products from the Heptalene-Forming Reaction of Azulenes and Acetylenedicarboxylates in Polar Media

Addition of Organochromium Reagents to Carbonyl Compounds

Recent Advances in Phase‐transfer Catalysis

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