Josuke Tsunetsugu

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

Hydrolysis of the spiro[2.4]hepta-4,6-diene–dichloroketen adduct (2a) gave 3-(2′-acetoxyethyl)-1H-cycloheptatrien-1-one (3a) and dihydro-8H-cyclohepta[b]furan-8-one (4a), of which the former was the precursor to the latter. 1-Methylspiro[2.4]hepta-4,6-diene– and spiro (cyclopropane-1,1′-[1H]-indene)–dichloroketen adducts, (2b), (2c), and (6), gave similar results.The spiro[4.4]nona-1,3-diene–dichloroketen adduct (10) gave spiro[4,6]undeca-8,10-diene-6,7-dione (14), 6-hydroxy-1,2,3,4-tetrahydro-5H-benzocyclohepten-5-one (15) and -7H-benzocyclohepten-7-one (16), and 5-acetoxy- and 5-hydroxy-7-chlorospiro(bicyclo[3.2.0]hept-2-ene-4,1′-cyclopentane)-6-ones, (12) and (13). The spiro (cyclopentane-1,1′-[1H]-indene)–dichloroketen adduct (19) gave similarly spiro (5H-benzocycloheptene-5,1′-cyclopentane)-6,7-dione (22).The formation of these compounds, especially the seven-membered ring, can be explained by the application of Bartletts mechanism to Stevens tropolone synthesis.

Synthesis and properties of cyclohepta[fg]naphth[2,3-a]acenaphthylene-5,12-dione (naphth[2,3-h]acepleiadylene-5,12-dione)

Naphth [2,3-h]acepleiadylene-5,12-dione (4) has been synthesized by the cycloaddition of acepleiadylene-5,8-dione (2) and o-dibromoquinodimethane generated in situ from 1,2-bis(dibromomethyl)benzene and sodium iodide. On the basis of their reduction potentials, determined by cyclic voltammetry, compound (4) and benz[h]acepleiadylene-5,10-dione (3) were shown to be [22]- and [18]-annulenediones, respectively. An unsuccessful attempt to synthesize naphth[2,3-h]acepleiadylene (7) is also described.

o-Pleiadienequinones. Part 2. Nucleophilic substitution reaction of o-pleiadienequinone with alcohols

In the course of the synthesis of the title compound (5) by the hydrolysis of the dichloro ketone (2) the acetoxy chloro ketone (6) was formed and accounted for in terms of the unusual bridgehead cation (3b). The nucleophilic substitution reaction of the compound (5) with various alcohols afforded alkoxy quinones (8) and/or acetals (7). The mechanism of the formation is discussed. The full characterization of 1-, 3-, and 6-methoxy quinones (8a1), (8a2), and (8a3) by spectroscopic and electrochemical methods is described. An attempt to effect the de-O-methylation of the methoxy quinones (8a), by the action of trimethylsilyl iodide, failed; dihydro quinones (15a), (15b), and (15c) resulted. The oxidative rearrangement of compound (5) to γ-lactone (17) in the reaction with iron(III) sulphate is described.

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

Acepleiadylene-5,8-dione (1) and acepleiadylene-5,6-dione (2) have been synthesized by the stepwise oxidation of 6,7-dihydrocyclohept[fg]acenaphthene-5,8-dione (4) and 7,8-dihydrocyclohept[fg]acenaphthene-5,6-dione (21) derived from compound (4), respectively. The reduction potentials of compounds (1) and (2) were determined by cyclic voltammetry which showed that E1=–0.50 V and E2=–0.84 V for the former, and E1=E2=–0.29 V for the latter. Spectral and electrochemical data suggest that both diones (1) and (2) are [14]annulenediones with a vinyl cross-link. 5,8- and 5,6-Dihydroxyacepleiadylene, (9′) and (22′), exist in their keto-forms, 6,7-dihydrocyclohept[fg]acenaphthylene-5,8-dione (9) and 7,8-dihydrocyclohept[fg]acenaphthylene-5,6-dione (22), respectively.

Synthesis and properties of cyclohepta[de]naphthalene-7,8-dione, o-pleiadienequinone

Cyclohepta[de]naphthalene-7,8-dione, o-pleiadienequinone (2), was synthesized by hydrolysis of the acenaphthylene–dichloroketene adduct (5); chloro(hydroxy)ketone (6) was the precursor. Compound (2) afforded the triacetate (16) by a Thiele–Winter-type reaction and a phenalene compound (19) by alkaline hydrolysis. Spectral data suggest that the dione (2) has contributions from such canonical forms as 2,3-(2a) and/or 4,5-benzotropolonate (2b) structures. The polarographic E½ value of the dione (2) is –0.23 V at pH 5.28 which is between that of 1,2-naphthoquinone and anthraquinone.

Synthesis of benzocyclo-octene-5,6-dione, benzocyclo-octene-5,10-dione, and 2,3-benzobishomotropone derivatives by dichlorocarbene ring enlargement, and of 7,8,9,10, tetrahydrobenzocyclo-octene-5,6-dione

Addition of dichlorocarbene by the use of a phase transfer catalyst to 1,4,5,8-tetramethoxynaphthalene (5) and to 2,3,4,6-tetramethoxybenzocyclohepten-5-one (9) afforded benzocyclo-octene-5,10-dione (2) and benzocyclo-octene-5,6-dione (4) together with 1,2:3,4-dimethylenenaphthalene (6) and 2,3-benzobishomotropone (10), respectively. Compounds (2) and (4) had no 8C-6π character. 7,8,9,10-Tetrahydrobenzocyclo-octene-5,6-dione (14) was synthesized by three different methods from 7,8,9,10-tetrahydrobenzocyclo-octen-5(6H)-one (12). This compound had an unusually rigid conformation and could not be converted into the benzocyclo-octene-5,6-dione (3).

The synthesis and electrochemistry of acepleiadylene-5,6-dione and acepleiadylene-5,8-dione

The acepleiadylenediones (1) and (2) have been synthesized and their reduction potentials determined by cyclic voltammetry show that they may be regarded as [14]annulenediones with an unexpectedly high quinone character.

Small ring-annelated non-benzenoid aromatic compounds: 1,2-dihydrocyclobuta[e]tropolone

1,2-Dihydrocyclobuta[e]tropolone, formed by ring-enlargement of benzocyclobutene-4,5-quinone with diazomethane, exists in tautomeric equilibrium almost exclusively as one tautomer; the methyl ethers formed on methylation correspond to a 1 : 1 mixture of the two tropolone tautomers.

Nonbenzenoid aromatic compounds containing a fused four-membered ring. Formation and properties of benzo[3,4]cyclobuta[1,2]cyclohepten-6-one derivatives

The ring-enlargement reaction of 1-methoxybiphenylene with dichlorocarbene gives 5-chlorobenzo[3,4]cyclobuta[1,2]cyclohepten-6-one (6) as well as fluorenone derivatives (7) and (8), although in low yields. Similar reactions of 2-methoxybiphenylene and its derivatives give the corresponding benzocyclobutacycloheptenones (11), (12), (14), (15), (17), and (18). The spectral data of the benzocyclobutacycloheptenones suggest that the four-membered ring assumes a tetramethylenecyclobutane (or dimethylenecyclobutene) form, excluding a potential cyclobutadiene form, and the seven-membered ring resembles the tropone ring of benzocycloheptenone.

Dichlorocarbene addition to 1-methoxybiphenylene. Formation of a benzo[3,4]cyclobuta[1,2-c]tropone derivative

1-Methoxybiphenylene (1) reacts with dichlorocarbene to give 1-chlorobenzo[3,4]cyclobuta-[1,2-c]tropone (2) and two fluorenone derivatives (3) and (4).