Synthesis of Functionalized Norcaradiene Derivatives

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Utilization of norcaradiene-cycloheptatriene valence isomerization, one of the most typical valence isomerization, was attempted for a development of new functinalized materials.(1) Attempt to develop a new solvatochromic system ; Control of norcaradiene-cycloheptatriene valence isomerization has been accomplished in 1,7-lactone and 1,7-lactam ring fused norcaradienes by protonation. Remarkable carbon chemical shift change was observed.(2) Conformational control of 1,7-lactol ring fused norcaradienes ; Using intramolecular hydrogen bonding, the restricted rotation occurring in the norcaradiene system was locked. This locking was unlocked by the solvation with alcohol or dimethyl sulfoxide.(3) Selective cleavage of cyclopropane sigma-bond of norcaradiene ; The C_1-C_7 bond of 1,7-lactol ring fused norcaradienes was selectively and conveniently cleaved to result in the dehydrative aromatization.(4) Mechanism of the hydrogen transferred photorearrangement ; In order to elucidate the mechanism of the hydrogen transferred photorearrangement often reported in the photo [2+2] cycloaddition, photochemistry of cyclopropene derivatives (synthetic intermediate for norcaradienes) was investigated. It was found that steric factors controlled the course of photoreaction whether a [2+2] cycloaddition or a hydrogen transferred rearrangement.