Synthesis of azulene-1-alkanoic acids, azulene-1,3-dialkanoic acids, and related compounds. A 1,3-bridged azulene

Anderson, Arthur G.; Breazeale, R. D.

doi:10.1021/jo01260a027

Cited by 30 publications

(8 citation statements)

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“…The spatial closeness and nearly parallel orientation of H or Me substituents at C(10) and C ( 14) as well as at C(3) and C(11) is also expressed in strong 'H-NOE, thus allowing to distinguish easily between 'anti'-and 'syn '-orientations of substituents at these positions (cf. also [l] [2]).…”

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confidence: 99%

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

Chen

Hansen

1993

Helvetica Chimica Acta

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It is shown that azulene (1) and dimethyl acetylenedicarboxylate (ADM) in a fourfold molar excess react at 200° in decalin to yield, beside the known heptalene-(5) and azulene-l,2-dicarboxylates (6), in an amount of 1.6% tetramethyl ( 1RS,2RS,5SR,8RS)-tetracyclo[6.2.2.22~5O'~5~tetradeca-3,6,9,l 1,13-pentaene-3,4,9,lO-tetracarboxylate ('anti'-7) as a result of a SHOMO(azulene)/LUMO(ADM)-controlled addition of ADM to the seven-membered ring of 1 followed by a Diels-Alder reaction of the so formed tricyclic intermediate 16 (cf: Scheme 3 ) with a second molecule of ADM. The structure of 'anti'-7 was confirmed by an X-ray diffraction analysis. Similarly, the thermal reaction of 5,7-dimethylazulene (3) with excess ADM in decalin at 120° ied to the formation of eu. 1 % of 'anti'-12, the 7,12-dimethyl derivative of 'anti'-7, beside of the corresponding heptalene-10 and azulene-l,2-dicarboxylates 11 (cf. Scheme 2 ) . The introduction of Me groups at C(l) and C(3) of azulene (1) and its 5,7-dimethyl derivative 3 strongly enhance the themial formation of the corresponding tetracyclic compound. Thus, 1,3-dimethylazulene (2) in the presence of a sevenfold molar excess of ADM at 200" yielded 20% of 'anli'-9 beside an equal amount of dimethyl 3-methylazulene-l,2-dicarboxylate (8; cf. Scheme I ) , and 1,3,5,7-tetramethylazulene (4) with a fourfold molar excess of ADM at 200' gave a yield of 37% of 'unti'-15 beside small amounts of the corresponding heptalene-13 and azuIene-1,2-dicarboxylates 14 (cf. Scheme 2 ) .

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confidence: 99%

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

Chen

Hansen

1993

Helvetica Chimica Acta

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“…However, the AM1-calculated DH o f values in Table 6 indicate that, in such a case, there would be an energetically much better path for a collapse of endo-23, namely to form the tetracyclic endo-10,2-product 26, which is favored over endo-25 by almost 13 kcal´mol À1 according to their AM1-calculated DH o f value (cf. [24]), a procedure that is very successful in the case of azulene-1-carbaldehydes (cf., e.g., [18a] [25]), failed since 2 was destroyed under the reaction conditions, we were able to perform a Wittig reaction with 2 and benzylidene(triphenyl)l 5 -phosphane in THF at À 78 to 08. The corresponding 8-styrylhomoheptalene 28 was obtained in almost quantitative yield as a 1.6 : 1 (Z)/(E)-mixture.…”

Section: Scheme 4)mentioning

confidence: 99%

New Results in Homoheptalene Chemistry

Rüedi

Hansen

2001

HCA

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The thermal reaction of homoazulene ( bicyclo[5.3.1]undeca-1,3,5,7,9-pentaene; 2) with dimethyl acetylenedicarboxylate (ADM) in 1,2-dichloroethane (ClCH 2 CH 2 Cl) results, in contrast to an earlier report [5], in formation of not only dimethyl homoheptalene-4,5-dicarboxylate ( bicyclo[5.5.1]trideca-1,3,5,7,9,11-hexaene-4,5-dicarboxylate; 3), but also of a 4 : 1 mixture of 3 and dimethyl homoheptalene-2,3-dicarboxylate (13) in almost quantitative yield (Schemes 1 and 3). The structures of both homoheptalenes have been corroborated by X-ray crystal-structure analysis (Fig. 5). The double-bond-shifted (DBS) isomers 3' and 13' of 3 and 13, respectively, could not be detected in their 1 H-NMR spectra (600 MHz threshold of detection ! 0.5%), in agreement with the AM1-calculated DH o f values of the four isomeric homoheptalene-dicarboxylates (cf . Table 4). Vilsmeyer formylation of homoazulene (2) gave homoazulene-8-carbaldehyde (14) in a yield of 67%, which, on treatment with benzylidene-(triphenyl)-l 5 -phosphane, gave, in almost quantitative yield, a 1.6 : 1 mixture of (Z)-and (E)-8-styrylhomoazulene ((Z)-15 and (E)-15, resp.). Thermal reaction of the latter mixture with ADM in 1,2-dichloroethane led, in a yield of 42%, to a 5 : 1 mixture of dimethyl (Z)-and (E)-2-styrylhomoheptalene-4,5-dicarboxylate ((Z)-15 and (E)-16, resp.). Both isomers were separated by column chromatography on silica gel. Again, the DBS isomers of (Z)-16 and (E)-16, i.e., (Z)-16' and (E)-16', could not be detected in the 1 H-NMR spectra (600 MHz) of pure (Z)-16 and (E)-16.1. Introduction. ± The class of homoheptalenes ( bicyclo[5.5.1]trideca-1,3,5,7,9,11-hexaenes) is still sparsely populated, although the parent structure was synthesized more than 25 years ago by Vogel et al.[1]. Line-shape analysis of the 13 C-NMR signals of homoheptalene (1a) in the temperature range of 153 ± 233 K gave an activation energy (E a ) of 5 kcal´mol À1 for the double-bond-shift (DBS) process in this [12]annulene, which is slightly higher than that for heptalene itself (3.5 kcal´mol À1 ), which was derived by the same procedure [2]. Two X-ray crystal-structure analyses of the homoheptalene derivatives 1b [3] and 1c [4] have been performed (see below) that show the p-core to be composed of two cycloocta-2,4,6-triene substructures with the homo-C(sp 3 )-atom and its two attached C(sp 2 )-atoms in common and with a c 2 axis passing through the bridging C-atom (see the AM1-calculated structure of 1a in Fig. 1, which is in good agreement with the X-ray crystal structures of 1b and 1c (Sect. 2.2). Later, Scott and Kirms applied Hafners synthesis of dimethyl heptalene-4,5-dicarboxylates by thermal reaction of azulenes and dimethyl acetylene-dicarboxylate (ADM) (cf.[5]) to homoazulene (2), for which Scott et al. had developed a new and efficient synthesis [6]. They reported that 2 reacts smoothly with ADM in boiling 1,2-dichloroethane (ClCH 2 CH 2 Cl) to yield b 90% dimethyl homoheptalene-4,5-dicarboxylate (3) 2 ) (Scheme 1) [5]. Apart from the specific case of benzo[b...

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“…46 Charge-transfer interaction plays an important role in a reaction. This would indicate the presence of only weak CT interaction.…”

Section: Ct Interactionmentioning

confidence: 99%

Nonbenzenoid Cyclophanes

Itô

Fujise

Fukazawa

1983

Organic Chemistry: A Series of Monographs

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Synthesis of azulene-1-alkanoic acids, azulene-1,3-dialkanoic acids, and related compounds. A 1,3-bridged azulene

Cited by 30 publications

References 8 publications

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

Thermal Reaction of Azulene and Some of Its Symmetrically Substituted Methyl Derivatives with Dimethyl Acetylenedicarboxylate

New Results in Homoheptalene Chemistry

Nonbenzenoid Cyclophanes

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