Thermolysis and Reactions of 4,5‐Benzotricyclo[4.1.0.0^1,3]hept‐4‐ene and o‐(Propadienyl)styrene

Abstract

influenced by the bridging; the conformation preferred in the crystal (see Fig. 2) is not crown-but saddle-shaped, as in 1,4,7-tro~onin['~]. Since the change in conformation in all these cases161 is not likely to require much extra energy, 3 and 4 may, like the parent system, be regarded as potential novel crown ether-like ligands for metal complexes. r 1

Synthesis and Reactivity of trans-Tricyclo[4.2.0.01,3]oct-4-ene

“…This interaction should be reflected in the thermal behavior of these tricyclic olefins. Consistent with this notion, 4,5-benzotricyclo[4.1.0.0 1,3 ]hept-4-ene ( 3 ) dimerizes and rearranges to 2-methylnaphthalene at 30 °C 2c. It has been suggested that spiro tricycloheptene 2 has eluded isolation because of a facile [σ 2s + π 2s + σ 2s ] pericyclic rearrangement initially leading to 5-methylene-1,3-cyclohexadiene, which subsequently undergoes a hydrogen shift to afford toluene. 2b,c, Tricyclo[4.2.0.0 1,3 ]oct-4-ene ( 1 ) contains only an extra methylene group in comparison to tricyclo[4.1.0.0 4,6 ]hept-2-ene ( 2 ).…”

“…Consistent with this notion, 4,5-benzotricyclo[4.1.0.0 1,3 ]hept-4-ene ( 3 ) dimerizes and rearranges to 2-methylnaphthalene at 30 °C 2c. It has been suggested that spiro tricycloheptene 2 has eluded isolation because of a facile [σ 2s + π 2s + σ 2s ] pericyclic rearrangement initially leading to 5-methylene-1,3-cyclohexadiene, which subsequently undergoes a hydrogen shift to afford toluene. 2b,c, Tricyclo[4.2.0.0 1,3 ]oct-4-ene ( 1 ) contains only an extra methylene group in comparison to tricyclo[4.1.0.0 4,6 ]hept-2-ene ( 2 ). Thus, in principle, tricyclo[4.2.0.0 1,3 ]oct-4-ene ( 1 ) could undergo an analogous pericyclic rearrangement which would thermally destabilize the system and, potentially, lead to the formation of spirobicyclo[5.2]octa-2,4-diene.…”

“…Structures and properties of small-ring bridged spiro hydrocarbons such as spiropentane and spirohexane have been a topic of interest for many years . These compounds are challenging synthetic targets since they possess a high degree of both torsional and angular strain which often results in unusual rearrangements and new synthetic transformations represents a novel structure that contains fused three-, four-, and five-membered rings and a carbon−carbon double bond.…”

“…trans -Tricyclo[4.2.0.0 1,3 ]oct-4-ene ( 1 ) represents a novel structure that contains fused three-, four-, and five-membered rings and a carbon−carbon double bond. Even though a variety of saturated bridged spiropentanes and spirohexanes containing 0−3 methylene groups has been reported ( 4 ), there is only one known compound, 4,5-benzotricyclo[4.1.0.0 1,3 ]hept-4-ene ( 3 ), with a two-carbon unsaturated bridge 2c …”

“…Synthesis of bridged spiro hydrocarbons is typically accomplished via intramolecular addition of small ring carbenes (i.e., divalent carbon in three- or four-membered rings) to double bonds. , Nevertheless, an attempt to synthesize tricyclo[4.2.0.0 1,3 ]octane ( 5 ), the saturated analogue of compound 1 , by such an approach was not successful primarily due to a competing ring contraction reaction and 1,2-hydrogen migration to give methylenecyclopropane and cyclobutene derivatives, respectively (eq 1) 1a. Therefore, in the synthesis of tricyclo[4.2.0.0 1,3 ]oct-4-ene ( 1 ) an intramolecular cyclization sequence originally described by Carpino, Gund, Springer, and Gund in 1981 was used to prepare gem -dichloro ketone 6 , which contains the complete tricyclic skeleton.…”