ChemInform Abstract: THERMAL ISOMERIZATION OF CHLORINE‐CONTAINING BICYCLOPROPYLIDENES

Synthesis of Methylene- and Alkylidenecyclopropane Derivatives

“…Additional ring strain in BCP is the factor which determines complete reversal of the equilibrium to methylenespiropentane 349 ,16a which has a lower energy strain content of about 12 kcal/mol. The same difference operates in substituted BCPs (Scheme ). 16c,,,− A similar rearrangement has been observed in a substituted adamantylidenecyclopropane 139 …”

“…A thermal rearrangement analogous to the one previously described occurs with vinylidenecyclopropane 424 and a series of isobutenylidenecyclopropanes to give, often as the exclusive products, dimethylenecyclopropane and its corresponding dimethyl derivatives, respectively (Scheme ). 16c,,,,− An unusual rearrangement was displayed by the fused alkenylidenecyclopropane 357 which gave exclusively the ACP 358 by heating in refluxing benzene (Scheme ) 142 …”

“…378 gem-Dialkoxy ACPs 353 were found to isomerize at low temperature (40-100 °C) in a reversible manner, as shown by isotope and chemical labeling A thermal rearrangement analogous to the one previously described occurs with vinylidenecyclopropane 424 and a series of isobutenylidenecyclopropanes to give, often as the exclusive products, dimethylenecyclopropane and its corresponding dimethyl derivatives, respectively (Scheme 142). 16c, 82,386,410,[425][426][427] An unusual rearrangement was displayed by the fused alkenylidenecyclopropane 357 which gave exclusively the ACP 358 by heating in refluxing benzene (Scheme 142). 428 A different rearrangement from alkenylidenecyclopropanes occurred under catalysis of strong bases, or in peculiar cases by thermolysis, to give allylidenecyclopropanes which were trapped or evolved into other products.…”

Thermal Rearrangements of Bicyclopropylidene and Substituted Bicyclopropylidenes − A Gas Phase Kinetic and Product Study

“…Analogous transformations have been reported for the tetramethylbicyclopropylidene 4, [7] a dichlorotetramethylbicyclopropylidene, [8] and 1,1-dideuteriobicyclopropylidene. [9] The mechanistic and kinetic aspects of these rearrangements have been reviewed, together with subsequent transformations of the resulting methylenespiropentane into dimethylenecyclobutane derivatives at higher temperatures.…”

The Thermal Transformations of Bicyclopropylidene and Methylenespiropentane Revisited

“…Analogous transformations have been reported for isomeric tetramethylbicyclopropylidenes,7b,7c dichlorotetramethylbicyclopropylidenes7d and 1,1‐dideuteriobicyclopropylidene 7e. The mechanistic, kinetic and preparative aspects of these reactions have been reviewed 6a,8.…”