Zur Kenntnis Der Azulene II. Die Substitution Von Azulenen Mit Metallorganischen Verbindungen

Häfner, Klaus; Weldes, Helmut H.

doi:10.1002/jlac.19576060110

Cited by 74 publications

(27 citation statements)

References 17 publications

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“…6(3) 137.9(4) 136.0 (3) 138.5(4) 142. 2(3) 140.0(4) 136.1 (3) 137.6(4) 138.6(3) distinctly alternating pattern of bond lengths around the seven-membered ring.…”

Section: In Parentheses) Of 9-phenylbenz[ A]azulene (4) and 4-phenylamentioning

confidence: 99%

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An Analysis of the Bonding Properties of Benz[a]azulene by X‐Ray, NMR, and Computational Studies

Bühl¹,

Koźmiński²,

Linden³

et al. 1996

Helvetica Chimica Acta

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Dedicated to Edgar Heilbronner on the occasion of his 75th birthday (1 .II. 96)The X-ray crystal structures of 9-phenylbenz[a]azulene (4) and the corresponding non-benzannelated form, 4-phenylazulene (9, have been determined (cf. Fig. 2). In contrast to 5, the skeleton of which shows nearly equal C,C bond lengths (cf: Table l ) , the seven-membered ring of 4 exhibits clearly alternating C,C bond lengths (cf. Table I ) . This is in agreement with a strong accentuation of the heptafulvene substructure in 4 by the [a] benzannelation. The alternating bond lengths of 4 and of its parent structure 3 are also reflected in the corresponding variations of the 'J(H,H) and 'J('3C,'3C) values of these benz[a]azulenes (cf. Tables4 and 5 ) . Computations on the MP2/6-3 1G* level as well as on the BP86/6-31G* level for azulene (6), benz[a]azulene (3), and heptafulvene (7) are in good agreement with the experimental values (cf. Tables 6-8).

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“…6(3) 137.9(4) 136.0 (3) 138.5(4) 142. 2(3) 140.0(4) 136.1 (3) 137.6(4) 138.6(3) distinctly alternating pattern of bond lengths around the seven-membered ring.…”

Section: In Parentheses) Of 9-phenylbenz[ A]azulene (4) and 4-phenylamentioning

confidence: 99%

“…Compound 5 had already been prepared and reported as a blue oil [3]. Fortunately, carefully purified 5 crystallized from hexane as blue prisms (m.p.…”

mentioning

confidence: 99%

An Analysis of the Bonding Properties of Benz[a]azulene by X‐Ray, NMR, and Computational Studies

Bühl¹,

Koźmiński²,

Linden³

et al. 1996

Helvetica Chimica Acta

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“…First, only electron-deficient aromatic rings, such as those in nitroarenes, [6] transition-metal complexes of arenes, [7] azulenes, [8] and azines, [9] can add nucleophilic agents, a process paralleling the first, rate-limiting step of electrophilic substitution. Second, to form substitution products, the adducts of nucleophiles to electron-deficient arenes should lose substituents with an electron pair that, for obvious reasons, cannot be hydride anions.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on the Electrophilic Activity of Nitroarenes in Reactions with Carbanions

Błażej

Mąkosza

2008

Chemistry A European J

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The effect on electrophilic activity of substituents located para, ortho, and meta to the nitro group of nitrobenzenes was determined by using vicarious nucleophilic substitution of hydrogen (VNS) with the carbanion of chloromethyl phenyl sulfone (1) as the model process. Values for the relative activities of substituted nitroarenes are given relative to nitrobenzene, which was taken as the standard. This process was chosen as a model reaction because it meets key criteria, such as the wide range of substituents that can be present on the nitrobenzene ring, a low sensitivity to steric hindrance, and in particular the possibility of ensuring conditions in which the overall relative rates of reaction in competitive experiments are equal to the relative rates of nucleophilic addition. The values of relative rates of addition, which were taken to be a measure of electrophilic activity, were determined by competitive experiments in which pairs of nitroarenes competed for the VNS reaction with carbanion of 1. A comprehensive set of data for effects of substituents on the electrophilic activity of nitroarenes is presented for the first time.

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“…Their structure followed from their 'H-NMR and mass spectra. The appearance of these four products as well as the missing of a possible second symmetric bisadduct demonstrates that i) under the conditions of the 'aid synthesis', is kinetically more acidicx) ') Sodium-salt formation of 10 with sodium inethylphenylamidc in Et,O at -1 5" occurs according to Hufi7c~ and Wr./drs [24] exclusively at '8 than Me-C(4/8) assuming equal reactivities of the formed carbanions with 22a, and i i ) the acidities of the residual Me groups in the mono-and bisadducts 28 to 30 are of similar magnitude and close to those of the Me groups of 10. The compounds 28-31 were stable under the reaction conditions, i.e., no styryl derivatives were formed, when they were treated with KOH as well as with t-BuOK in DMF.…”

Section: Spectru (Hexane) Of 7-isopropyl-l-methyl-4-( ( E)-4-r-styrmentioning

confidence: 97%

New Results in the Synthesis of Styrylazulene Derivatives: Application of the ‘Anil synthesis’ to the preparation of azulenes substituted with styryl groups at the seven‐membered ring

Briquet

Hansen

1994

Helvetica Chimica Acta

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The synthesis of 4,6,8-trimethyl-l-[(E)-4-R-styryl]azulenes 5 (R=H, MeO, Cl) has been performed by Wittig reaction of 4,6,8-trimethylazulene-1-carbaldehyde (1) and the corresponding 4-(R-benzyl)(triphenyl)phosphonium chlorides 4 in the presence of EtONa/EtOH in boiling toluene (see Table 1 ). In the same way, guaiazulene-3carbaldehyde (2) as well as dihydrolactaroviolin (3) yielded with 4a the corresponding styrylazulenes 6 and 7, respectively (see Table 1). It has been found that 1 and 4b yield, in competition to the Witfig reaction, alkylation products, namely 8 and9, respectively (cf. Scheme I ). Thereaction of4,6,8-trimethylazulene(l0) with 4b in tolueneshowed that azulenes can, indeed, be easily alkylated with the phosphonium salt 4b. 4,6,8-Trimethylazulene-2carbaldehyde (12) has been synthesized from the corresponding carboxylate 15 by a reduction (LiAlH,) and dehydrogenation (MnOz) sequence (see Scheme 2). The Swern oxidation of the intermediate 2-(hydroxy-methy1)azulene 16 yielded only 1,3-dichloroazulene derivatives (cf: Scheme 2). The Witrig reaction of 12 with 4a and 4b in the presence of EtONa/EtOH in toluene yielded the expected 2-styryl derivatives 19a and 19b, respectively (see Scheme 3 ) . Again, the yield of 19b was reduced by a competing alkylation reaction of 19b with 4b which led to the formation of the I-benzylated product 20 (see Scheme 3 ) . The 'anil synthesis' of guaiazulene (21) and the 4-R-benzanils 22 (R=H, MeO, C1, Me,N) proceeded smoothyl under standard conditions (powered KOH in DMF) to yield the corresponding 4-[(E)-styryl]azulcne derivatives 23 (see Table 4 ) . In minor amounts, bis(azulen-4-yl) compounds of type 24 and 25 were also formed (see Table 4 ) . The 'anil reaction' of 21 and 4-NOZC,H,CH=NC,H, (22e) in DMF yielded no corresponding styrylazulene derivative 23e. Instead, (E)-1,2-bis(7isopropyl-1-methylazulen-4-yl)ethene (27) was formed (see Scheme 4 ) . The reaction of 4,6,8-trimethylazulene (10) and benzanil (22a) in the presence of KOH in DMF yielded the benzanil adducts 28 to 31 (cf: Scheme 5 ) . Their direct base-catalyzed transformation into the corresponding styryl-substituted aznlenes could not be realized (qf. Scheme 6). However, the transformation succeeded smoothly with KOH in boiling EtOH after N-methylation (cfi Scheme 6).

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Zur Kenntnis Der Azulene II. Die Substitution Von Azulenen Mit Metallorganischen Verbindungen

Cited by 74 publications

References 17 publications

An Analysis of the Bonding Properties of Benz[a]azulene by X‐Ray, NMR, and Computational Studies

An Analysis of the Bonding Properties of Benz[a]azulene by X‐Ray, NMR, and Computational Studies

Substituent Effects on the Electrophilic Activity of Nitroarenes in Reactions with Carbanions

New Results in the Synthesis of Styrylazulene Derivatives: Application of the ‘Anil synthesis’ to the preparation of azulenes substituted with styryl groups at the seven‐membered ring

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