1,1-Ethylene-1H-azulenium ion and its alkyl substituted derivatives: Synthesis, characterization, and some reactions thereof

Oda, Mitsunori; Kajioka, Takanori; Uchiyama, Takuya; Nagara, Kohki; Okujima, Tetsuo; Ito, Shunji; Morita, Noboru; Sato, Toshio; Miyatake, Ryuta; Kuroda, Shigeyasu

doi:10.1016/s0040-4020(99)00280-x

Cited by 11 publications

(9 citation statements)

References 40 publications

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“…Note that the structure of 13 is unusual; cyclizations of various cycloheptatrienylethanones 15 under the same reaction conditions yielded 1,2,3,8-tetrahydroazulen-1-ones instead of the 1,2,3,3a-isomer 16 (Scheme 2). [3,4,5,7] Since the Nazarov cyclization is believed to proceed through 4π-conrotatory electrocyclization of a protonated intermediate 18, [10,13] this study is rationalized based on density functional theory (DFT) calculations [14] of possible enol intermediates, 20 and 21, as follows. Calculations at B3LYP/6-31G(d) level of theory predict that the enol 20 is more stable than 21 for the adamantaneconnected system, whereas the enol 20 is less stable than 21 for the cyclohexane-connected system (Figure 3).…”

Section: Resultsmentioning

confidence: 99%

“…The X-ray crystal structure of the title cation (ClO 4 -salt) reveals CH-O interactions and deformation of the azulenyl ion part.…”

Section: Entry For Thementioning

confidence: 99%

“…The aqueous layer was extracted with dichloromethane (50 ml × 2). The combined organic layer was washed with a saturated NaHCO 3 aqueous solution and brine, and then dried over anhydrous MgSO 4 …”

Section: Synthesis Of 1-(cyclohepta-135-trienyl)-2-(2-methoxyadamanmentioning

confidence: 99%

“…The combined organic layer was washed with a saturated NaHCO 3 aqueous solution and brine, and then dried over anhydrous MgSO 4 ppm; 13 X-ray crystallographic analysis of 10: One crystal having approximate dimensions of 0.40 × 0.30 × 0.50 mm was mounted on a glass fiber. All measurements were conducted using a Rigaku AFC7R diffractometer with graphite monochromated Mo-Kα radiation and a rotating anode generator.…”

Section: Synthesis Of 1'2'3'8a'-tetrahydrospiro[adamantane-21'-azmentioning

confidence: 99%

“…[1,2] Stability of cyclic π-conjugated carbocations, particularly shown as pK R + values, aids in understanding the capability of π−conjugation and the outcome of various structural effects on delocalized carbocations. We previously reported the syntheses of various 1,1-spiroalkylated 1H-azulenium cations 2-6 [3,4] and 1,1-dialkylated 1H-azulenium cations 7-9 [5] (Figure. 1).…”

Section: Introductionmentioning

confidence: 99%

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Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group

et al. 2008

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Starting from trimethylsilyl enol ether of 1-acetyl-1,3,5-cycloheptatriene, the title 1H-azulenium cation was synthesized by a five-step sequence that involves the Noyori-Mukaiyama aldol reaction, the Nazarov cyclization, the Shapiro reaction, and hydride abstraction. The Nazarov reaction of the aldol-type adduct resulted in formation of an unusual double-bond position isomer, which has never been obtained in similar reactions forming tetrahydroazulenones. The pK R + value of the title cation was found to be 9.8, which is less than that expected by inductive stabilization of the carbon number at the 1-position. The X-ray crystal structure of the title cation (ClO 4 -salt) reveals CH-O interactions and deformation of the azulenyl ion part.

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Section: Resultsmentioning

confidence: 99%

“…The X-ray crystal structure of the title cation (ClO 4 -salt) reveals CH-O interactions and deformation of the azulenyl ion part.…”

Section: Entry For Thementioning

confidence: 99%

Section: Synthesis Of 1-(cyclohepta-135-trienyl)-2-(2-methoxyadamanmentioning

confidence: 99%

Section: Synthesis Of 1'2'3'8a'-tetrahydrospiro[adamantane-21'-azmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group

et al. 2008

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Carbocations in Superacid Systems

Oláh¹,

Prakash²,

Molnár³

et al. 2008

Superacid Chemistry

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Calenzanane Sesquiterpenes from the Red Seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island: Acid‐Catalyzed Stereospecific Conversion of Calenzanol into Indene‐ and Guaiazulene‐Type Sesquiterpenes

Guella¹,

Skropeta²,

Mancini³

et al. 2003

Chemistry A European J

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It is shown here that calenzanane sesquiterpenes (1 and 6) can be isolated from organic extracts from the red seaweed Laurencia microcladia Kützing from the Bay of Calenzana, Elba Island, provided contact with acidic media is minimized. Such contact induces rearrangements of 1 in dry solvents to indene-type 5 and the blue-colored guaiazulenium-type ion 17, via spectrometrically (NMR) characterized indene-type transient intermediates 10, 14, and 12. Addition of NEt(3) to the reaction mixture at appropriate stages allowed the isolation of 12 (and 8 on workup on SiO(2)), and guaiazulene (18). Prolonged contact with silica gel led to complete degradation of 1, giving calenzanane-type epimeric enones 20 a/20 b as well as indene-type epimeric carbinols 22 a/22 b and fulvene 7. The latter was also formed during silica-gel flash chromatography of the algal extracts. A unifying mechanistic view of these branching and cascade transformations may have both heuristic value, suggesting possible artefact origin of azulenoids, and synthetic applications.

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1,1-Ethylene-1H-azulenium ion and its alkyl substituted derivatives: Synthesis, characterization, and some reactions thereof

Cited by 11 publications

References 40 publications

Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group

Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group

Carbocations in Superacid Systems

Calenzanane Sesquiterpenes from the Red Seaweed Laurencia microcladia from the Bay of Calenzana, Elba Island: Acid‐Catalyzed Stereospecific Conversion of Calenzanol into Indene‐ and Guaiazulene‐Type Sesquiterpenes

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