Benzotropolon

Benzotropolone has also been prepared by using the same method 88). 

Friedrichsen and co-workers (133) approached substituted benzotropolones from an aromatic substituted carbonyl ylide with a tethered alkyne as the intramolecular dipolarophUe (Scheme 4.67). Starting from an aromatic anhydride, Friedrichsen was able to make the tethered alkyne via addition of either pentyn-ol or hexyn-ol, then transform the recovered benzoic acid to the a-diazocarbonyl cycloaddition precursor. Addition of rhodium acetate resulted in the tandem formation of cyclic carbonyl ylide followed by cycloaddition of the tethered alkyne producing the tricyclic constrained ether 252. Addition of BF3 OEt2 opened the ether bridge, forming the benzotropylium ion, which subsequently rearranged to form the tricyclic benzotropolone (253). 

Peter H. Given. One of the important questions we have to solve in coalification is how polycyclic aromatic substances come to be formed. Was the benzotropolone positively identified This is an interesting way in which polycyclic compounds are formed from monocyclic. Is it your idea that quinone adducts are formed in the biochemical decay and that these adducts are transformed into polycyclic aromatics by the action of heat after burial ... 

Besides the fragmentation of the 6/6 and 6/5 annelated rings, a number of other ring combinations in bicycles have been investigated. A 6/3 system3), Scheme VIII/6, has been used to explain the observation that the unexpected 6,7-dimethyl-3,4-benzotropolone (VIII/33) is formed when an acetic acid solution of VIII/30 is treated with zinc powder [25]4). 

A number of cases are known of ring contraction of tropolones to phenols, with extrusion of the carbonyl group as carboxylate or carbon dioxide. Examples are the conversions of the benzotropolone (216) to the naphthol ester (217 73%) with methanolic potash the pyridinotropolone (218) to the quinoline (219 50%) in dilute alkali the aminotropolone (220) to the methylsalicyclic acid (221 82%) on diazotization and the tropolonecarboxylate (222) to the dicarboxylic acid (223 78%) on brief alkali fu-... 

Turner and Seden report a low yield synthesis of 4,5-benzotropolone from indene and dichloroketene. 

A recent review 74> summarizes many photochemical conversions of monocyclic tropolones, colchicine, isocolchicine, and benzotropolones to bicydo[3.2.0]hepta-3,6-dien-2-one derivatives. 

A theaflavin-related benzotropolone pigment having a procyanidin unit was synthesized in vitro. Although proanthocyanidin dimers have two B-rings, the condensation occurred regioselectively at the extension (upper) unit of the procyanidin due to steric effect. ... 

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