8.8- dimethylbicyclo octa-2.4-diene

Ring closure to cyclobutanes via valence isomerization of cycloocta-l,3,5-trienes is also possible when carbonyl functions are present in the ethane fragment. Thus, reaction of cyclohepta-2,4,6-trienone (tropone) with diazopropane gives 8,8-dimethylcycloocta-2,4,6-trienone (16, R = H), which rearranges quantitatively to 8,8-dimethylbicyclo[4.2.0]octa-2,4-dien-7-one (17, R = H).67... 

Tetramethyl 3,7-dihydroxy-1,5-dimethylbicyclo-[3.3.0]octa-2,6-diene-2,4,6,8-tetracarboxylate 1,3,4,6-Pentalenetetracarboxylic acid, 1,3a,4,6a-tetrahydro-2,5-dihydroxy-3a,6a-dimethyl-, tetramethyl ester (11) (79150-94-0) Biacetyl 2,3-Butanedione (8,9) (431-03-8)... 

Dimethylbicyclo[4.1.1]octa-2,4-diene (la) underwent rearrangement on direct photolysis or pyrolysis to yield 8,8-dimethylbicyclo[5.1.0]octa-2,4-diene (2a), a homolog of 7,7-dimethyl-norcaradiene (see Section 4.4.1.). This product, resulting from a 1,5-carbon shift, was the only isomer detected on irradiation through Pyrex or when the pyrolysis was conducted at 225 °C. Pyrolysis at 250°C gave a mixture of substituted cyclohepta-1,3- and -1,4-dienes 3 and 4. ... 

Dimethylbicyclo[4.1.1 ]octa-2,4-diene gave 8,8-dimethylbicyclo[5.1.0]octa-2,4-diene upon beating in a flow system with at least 80% inversion of configuration at C7, the migrating carbon in this 1,5-shift of carbon (Scheme 9.46). ... 

Dimethylcyclo-octa-1,5-diene reacts with boron trifluoride diethyl etherate to give 2,5-dimethylbicyclo[3,3,0]oct-2-ene (60%), whereas l,5-dimethylbicyclo[3,2,l] octan-8-ol (156 R = H 50%) and its tosylate (156 R = Ts 70%) are formed on treatment with perchloric acid-aqueous dioxan and toluene-p-sulphonic acid, respectively. Preliminary results indicate that cis,ci -cyclo-octa-l,5-diene and hydrogen peroxide-mercury(ii) nitrate react to give a transannular peroxide. The boron trifluoride diethyl etherate-benzene catalysed cyclizations of the cyclo-octenyl ester (157 R = COjEt) and ketone (157 R = COMe) to the bicyclo[3,3,l]nonanes (158 R = C02Et) and (158 R = COMe), respectively, have been studied further. Possible intermediates in these reactions were synthesized but no cyclized products were obtained. The mechanism that was finally suggested involves protonation of the... 

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