2,5,8,11,14,17-HEXA-T-BUTYLDECACYCLENE AND 1,7,13- 1,6,12-TRI-T-BUTYLDECACYCLENE - POSSIBLE PRECURSORS FOR BOWL-SHAPED POLYCYCLIC ARENES/

Decacyclene (2) was converted into 2,5,8,11,14,17-hexa-t-butyldecacycl ene (4) by Friedel-Crafts alkylation using t-butylchloride/aluminium c hloride in 1,2-dichlorobenzene. Dehydrogenating cyclotrimerization of 5-/-butylacenaphthene by reaction with elemental sulfur resulted in 1, 7,13- and 1,6,12-tri-t-butyldecacyclene (6a/6b) in the expected statis tical 1:3 isomeric ratio. Single crystal X-ray structure analysis show ed 4 to possess a non-planar, non-propeller C-l conformation in the cr ystal. According to molecular modelling (force field calculations) thi s non-propeller conformation is 12.7 kJ mol(-1) higher in energy than the expected D-3 propeller conformation. The observation of the energe tically unfavourable non-propeller molecular conformation in the cryst al is attributed to favourable crystal packing of the bulky t-butyl su bstituents. Copyright (C) 1996 Elsevier Science Ltd