Syntheses from perfluoro-2-butyne. 2. Perfluorooctamethylcubane, perfluorooctamethylcuneane, and perfluorooctamethylcyclooctatetraene

Photochemistry of Bridged and Unbridged Octaalkyl-Substituted syn-Tricyclo[4.2.0.02,5]octa-3,7-diene Derivatives

“…[1] In view of this fact, it is noteworthy that early attempts to synthesize octamethylcubane from octamethyltricyclo[4.2.0.0 2,5 ]octa-3,7-diene (1) failed. [2,3] This finding led to the tricyclo[4.2.0.0 2,5 ]octa-3,7-diene skeleton being considered photochemically inert. [4] This view has changed in the last few years.…”

“…The generation of the cubane-and cuneane-derivatives (3 and 4) from perfluorooctamethyl-syn-tricyclo[4.2.0.0 2,5 ]octa-3,7-diene (2) [5] (Scheme 1) could be caused by the strongly electron-withdrawing trifluoromethyl groups. Diene 1 rearranged to octamethylcyclooctatetraene (5) and the anti isomer of 1 (6) when irradiated in the presence of phthalic acid anhydride. [6] Other observations which demonstrate that the tricyclo[4.2.0.0 2,5 ]octa-3,7-diene skeleton is not photochemically inert are given in Scheme 1.…”

“…Diene 1 rearranged to octamethylcyclooctatetraene (5) and the anti isomer of 1 (6) when irradiated in the presence of phthalic acid anhydride. [6] Other observations which demonstrate that the tricyclo[4.2.0.0 2,5 ]octa-3,7-diene skeleton is not photochemically inert are given in Scheme 1. [7,8] Common to the photochemistry of 1, 7, and 9 was the observation that irradiation did not lead to the corresponding cubane.…”

“…[9,10] As a result of this orbital sequence photochemical [22] cycloaddition of 1 to cubane is a symmetryforbidden process. We entered this area of research via our study of the photochemistry of the fourfold bridged tricyclo[4.2.0.0 2,5 ]octa-3,7-diene derivative 12.…”

“…[11] The photochemistry observed for 12 led us to reinvestigate the thermal [12] and photochemical [13] behavior of 1 and some bridged tricyclo[4.2.0.0 2,5 ]octa-3,7-dienes. [12,13] In this paper we report on the photochemistry of syn-octamethyltricyclo[4.2.0.0 2,5 ]octa-3,7-diene (1), its octaethyl congener 15, syn-1,2,3,4, 5,6,7,8,9,10,11,12- (17).…”