3761-63-5Relevant academic research and scientific papers
SCOPE AND LIMITATIONS OF THE FLASH VACUUM THERMOLYSIS APPROACH TO SMALL PARACYCLOPHANES
Jenneskens, L. W.,Wolf, W. H. De,Bickelhaupt, F.
, p. 1571 - 1574 (2007/10/02)
Flash vacuum thermolysis (FVT) of 3-methylene-6-spirocyclohexa-1,4-dienes (2) was investigated as a synthetic approach to small paracyclophanes 1 (1a, n=8; 1b, n=7; 1c, n=6).The method was found to be preparatively attractive for 1a (80percent yield), less so for 1b (7percent useful yield), and not at all for 1c which was too unstable to survive the conditions of its formation.Besides 1, p-alkylstyrenes (3) and 2-methylbenzocycloalkenes (4) were obtained; the total recovery of monomeric products was good (60-85percent).The temperature dependence of product formation furnished useful information on the mechanisms of formation and decomposition of 1 under the conditions of FVT.
A comparative investigation of 1,4-pentamethylene and 1,4-hexamethylene Dewar benzene. Evidence for the intermediate formation of paracyclophane
Straten, J. W. van,Turkenburg, L. A. M.,Wolf, W. H. de,Bickelhaupt, F.
, p. 89 - 97 (2007/10/02)
The synthesis of the title compounds 1a and 1b is described.Starting from the corresponding 1,2-dimethylenecycloalkanes 6, the compounds 1 were obtained in four steps, viz. addition of dichlorocarbene, reduction with triphenyltin hydride, treatemnt with potassium tert-butoxide and silver-ion-catalyzed rearrangement.In the last step, the 1,2-isomers 11 of 1 were also formed, and their thermal rearrangement to the benzocycloalkenes 4 is briefly described.Compound 1b rearranged to its aromatic isomer (6)paracyclophane (2b) both thermally (60 deg C in solution, 100-460 deg C flow pyrolysis) and under silver-ion catalysis at room temperature; in this latter reaction the initially formed 2b was gradually further isomerized to 4b.At higher temperatures, 2b rearranged to the spirotrienes 3b and finally fragmented to give p-ethylstyrene (17).From 1a, the spirotriene 3a and benzocycloheptene (4a) were obtained by thermolysis and by silver-ion catalysis, respectively.The mechanism of these reactions is discussed and it is concluded that (5)paracyclophane (2a) is a transient intermediate in th reaction of 1a.
