Draft:Puberulic Acid
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Last edited by Pygos (talk | contribs) 4 hours ago. (Update) |
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| Names | |||
|---|---|---|---|
| IUPAC name
4,5,6-trihydroxy-3-oxocyclohepta-1,4,6-triene-1-carboxylic acid
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| Identifiers | |||
3D model (JSmol)
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| ChEMBL | |||
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| Properties | |||
| C8H6O6 | |||
| Molar mass | 198.13 g/mol | ||
| Density | 2.0 to 2.2 g/ml | ||
| Boiling point | 166.4 to 246.4 °C (331.5 to 475.5 °F; 439.5 to 519.5 K) (760 mmHg) | ||
| Hazards | |||
| GHS labelling:[1] | |||
  
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| Danger | |||
| H314, H317, H410 | |||
| P260, P261, P264, P272, P273, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P333+P313, P363, P391, P405, P501 | |||
| Flash point | 112 °C (234 °F; 385 K) | ||
| Related compounds | |||
Related compounds
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Hinokitiol (4-isopropyl-tropolone) | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Tropolone is an organic compound with the chemical formula C7H5(OH)O. It is a pale yellow solid that is soluble in organic solvents. The compound has been of interest to research chemists because of its unusual electronic structure and its role as a ligand precursor. Although not usually prepared from tropone, it can be viewed as its derivative with a hydroxyl group in the 2-position.
Synthesis and reactions[edit]
Many methods have been described for the synthesis of tropolone.[2] One involves bromination of 1,2-cycloheptanedione with N-bromosuccinimide followed by dehydrohalogenation at elevated temperatures, while another uses acyloin condensation of the ethyl ester of pimelic acid the acyloin again followed by oxidation by bromine.[3]
An alternate route is a [2+2] cycloaddition of cyclopentadiene with a ketene to give a bicyclo[3.2.0]heptyl structure, followed by hydrolysis and breakage of the fusion bond to give the single ring:[2]
Thy hydroxyl group of tropolone is acidic, having a pKa of 7, which is in between that of phenol (10) and benzoic acid (4). The increased acidity compared to phenol is due to resonance stabilization with the carbonyl group, as a vinylogous carboxylic acid.[3]
The compound readily undergoes O-alkylation to give cycloheptatrienyl derivatives, which in turn are versatile synthetic intermediates.[4] With metal cations, it undergoes deprotonation to form a bidentate ligand, such as in the Cu(O2C7H5)2 complex.[3]
The carbonyl group is also highly polarized, as common for tropones. There can be substantial hydrogen bonding between it and the hydroxyl group, leading to rapid tautomerization: the structure is symmetric on the NMR timescale.[5]
Natural occurrence[edit]
Around 200 naturally occurring tropolone derivatives have been isolated, mostly from plants and fungi.[6][7][8][9][10] Tropolone compounds and their derivatives include dolabrins, dolabrinols, thujaplicins, thujaplicinols, stipitatic acid, stipitatonic acid, nootkatin, nootkatinol, puberulic acid, puberulonic acid, sepedonin, 4-acetyltropolone, pygmaein, isopygmaein, procein, chanootin, benzotropolones (such as purpurogallin, crocipodin, goupiolone A and B), theaflavin and derivatives bromotropolones, tropoisoquinolines and tropoloisoquinolines (such as grandirubrine, imerubrine, isoimerubrine, pareitropone, pareirubrine A and B), colchicine, colchicone and others.[11] Tropolone arises via a polyketide pathway, which affords a phenolic intermediate that undergoes ring expansion.[4]
They are especially found in specific plant species, such as Cupressaceae and Liliaceae families.[8] Tropolones are mostly abundant in the heartwood, leaves and bark of plants, thereby the essential oils are rich in various types of tropolones. The first natural tropolone derivatives were studied and purified in the mid-1930s and early-1940s.[12] Thuja plicata, Thujopsis dolabrata, Chamaecyparis obtusa, Chamaecyparis taiwanensis and Juniperus thurifera were in the list of trees from which the first tropolones were identified. The first synthetic tropolones were thujaplicins derived by Ralph Raphael.[13]
Biological effects[edit]
References[edit]
- ^ "Tropolone". pubchem.ncbi.nlm.nih.gov.
- ^ a b Minns RA (1977). "Tropolone". Org. Synth. 57: 117. doi:10.15227/orgsyn.057.0117.
- ^ a b c Pauson PL (1955). "Tropones and Tropolones". Chem. Rev. 55 (1): 9–136. doi:10.1021/cr50001a002.
- ^ a b Pietra F (1973). "Seven-membered conjugated carbo- and heterocyclic compounds and their homoconjugated analogs and metal complexes. Synthesis, biosynthesis, structure, and reactivity". Chemical Reviews. 73 (4): 293–364. doi:10.1021/cr60284a002.
- ^ Jin L (February 1987). Detoxification of thujaplicins in living western red cedar (Thuja plicata Donn.) trees by microorganisms (PhD). University of British Columbia.
- ^ Bentley R (2008). "A fresh look at natural tropolonoids". Nat. Prod. Rep. 25 (1): 118–138. doi:10.1039/b711474e. PMID 18250899.
- ^ Guo H, Roman D, Beemelmanns C (2019). "Tropolone natural products". Natural Product Reports. 36 (8): 1137–1155. doi:10.1039/c8np00078f. PMID 30556819.
- ^ a b Zhao JZ (30 September 2007). "Plant Troponoids: Chemistry, Biological Activity, and Biosynthesis". Current Medicinal Chemistry. 14 (24): 2597–2621. doi:10.2174/092986707782023253. PMID 17979713.
- ^ Bentley R (2008). "A fresh look at natural tropolonoids". Nat. Prod. Rep. 25 (1): 118–138. doi:10.1039/b711474e. PMID 18250899.
- ^ Guo H, Roman D, Beemelmanns C (2019). "Tropolone natural products". Natural Product Reports. 36 (8): 1137–1155. doi:10.1039/c8np00078f. PMID 30556819.
- ^ Liu N, Song W, Schienebeck CM, Zhang M, Tang W (December 2014). "Synthesis of naturally occurring tropones and tropolones". Tetrahedron. 70 (49): 9281–9305. doi:10.1016/j.tet.2014.07.065. PMC 4228802. PMID 25400298.
- ^ Nakanishi K (June 2013). "Tetsuo Nozoe's "Autograph Books by Chemists 1953-1994": An Essay: Tetsuo Nozoe's "Autograph Books by Chemists 1953-1994": An Essay". The Chemical Record. 13 (3): 343–352. doi:10.1002/tcr.201300007. PMID 23737463.
- ^ Cook JW, Raphael RA, Scott AI (1951). "149. Tropolones. Part II. The synthesis of α-, β-, and γ-thujaplicins". J. Chem. Soc.: 695–698. doi:10.1039/JR9510000695.