Tetramethylene Dewar benzene

Dispiro[2.0.2.4]deca-1,5-diene and Tetramethylene Dewar Benzene 358... 

As an aside, silver ion catalyzes the conversion of the dispirodiene to both 1,2-and 1,4-tetramethylene Dewar benzene the former gives tetralin at room temperature, but the latter requires heating to 140°C to give p-xylylene-like polymers (Scheme 11.68). ... 

The latter reaction may proceed through [4]/7-cyclophane which was calculated (DZ + dTCSCF CISD +Q) to be 9.3 kcal/mol less stable than the 1,4-tetramethylene Dewar benzene. Further, the computed transition state enthalpy for the interconversion was calculated to be 31.2 kcal/mol above the Dewar benzene. 

Tetramethylene Dewar Benzene to 4-/7ieta-Cyclophane to Tetralin and Tetramethyleneprismane to Tetralin and Tetramethylene Fulvene... 

Flash vacuum pyrolysis of 2,5-tetramethylene Dewar benzene gives tetralin. However, the intermediacy of 4-m a-cyclophane and its benzvalene equivalent has been implicated in the reaction with deuterium labeling being consistent with the observations (Scheme 11.81). " ... 

Ramberg-Backlund reactions, discussed in more detail in Chapters 1 and 2, continue to be of great significance in the synthesis of strained alkenes. Bicyclo-[2,2,l]heptenes, [4,2,2]propellanes, 1,4-tetramethylene- and 1,4-penta-methylene-Dewar-benzene, and the ethylene ketal of hydrindane-3,6-dien-l-one have been prepared, utilizing this rearrangement as the final step. 2,5-Dialkyl-sulpholans have been converted, in synthetically useful yields (20— 67%), into 1,2-dialkyl-cyclobutenes upon reaction with Bu Li in THF followed by reduction with LiAlH4. This most interesting reaction has been applied to the preparation of a wide variety of fused benzocyclobutenes. ... 

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