SYNTHESIS OF PLEIADIENE-7,8-DIONE, o-PLEIADIENOQUINONE

Abstract

Pleiadiene-7,8-dione, o-pleiadienoquinone (I), was synthesized by hydrolysis of acenaphthylene-dichloroketene adduct (III). E1⁄2 value is −0.23 V at pH 5.28. Spectral data suggest that I has the contribution from such canonical forms as 2,3- (Ia) and/or 4,5-benzotropolonate (Ib) structures.

On Stevens' tropolone synthesis; hydrolysis of spirocyclopentadiene– and spiroindene–dichloroketen adducts

“…Hydrolysis of the spiro-compound (6)," a benzo-fused analogue of (2a) with sodium acetate in refluxing acetic acid as for compounds (2))afforded the benzo-fused tropolone (7) (8% yield) and the benzocycloheptafuranone (8) (68% yield). Under similar conditions of hydrolysis, the acetate (7) was transformed into compound (8) in 82% yield, again showing that (7) was the precursor of (8). 0 Scheme 4 interpreted only on the basis that the addition of dichloroketen gave a 6-rather than a 7-0x0-adduct.…”

“…The reaction of l-methylspiro[2.4]hepta-4,6-diene (I b) with dichloroketen led to a mixture of two adducts (2b) and (2c) (92.5% yield), in a ratio of 11 : 9 (n.m.r.). The position and configuration of the methyl group were not determined but consideration of molecular models indicated that compounds (2b) and (2c) were isomeric at position 8 and (2c) was hydrolysed as for (2a) to give the acetoxypropyltropolone (3b) (12.8% yield) and the methylcycloheptafuranone (4b) (26.7% yield). Hydrolysis of compound (3b) gave (4b), showing that it was a precursor of (4b).…”

Synthesis of naturally occurring tropones and tropolones

“…268 In the presence of sodium acetate in acetic acid, the four-five fused bicyclic compound could undergo enolization, addition/elimination, and fragmentation to form tropolone 75-4 . 269 This method was later applied to the total synthesis of various tropolones, 269–271 such as β-thujaplicin, by starting with isopropyl substituted cyclopentadiene 272 and a synthetic intermediate for colchicine ( 75-7 ) as shown in Scheme 75. 273 …”

Synthesis and properties of acepleiadylene-5,6-dione and acepleiadylene-5,8-dione

“…To synthesize acepleiadylene-5,6-dione (2) the diketone (4) was refluxed with ethylene glycol and toluene-p-sulphonic acid in dry benzene for five days to give the monoacetal(l6) (75.5%) but no diacetal. The carbonyl group of this compound (16) was reduced by the Wolff-Kishner reaction to the acetal(l7) (7579, which was subsequently converted into the monoketone (18) (82%) by 6~ hydrochloric acid. The monoketone (18) was allowed to react with 2.2 mol equiv.…”

“…-8(7H)-one (16).-Into a two-necked flask fitted with a Dean-Stark trap and condenser were placed the diketone (4) (9.09 g, 38.5 mmol), etheylene glycol (9 1 ml), toluene-p-sulphonic acid monohydrate (480 mg, 2.5 mmol), and dry benzene (500 ml). The contents were refluxed to separate water, and the apparatus was replaced by a Soxhlet extractor containing a mixture of anhydrous calcium sulphate and molecular sieve 4 8, in a filter paper thimble.…”