182. The Aluminum-Bromide-Catalyzed Adamantane Rearrangemet of syn- and anti-Tricyclo2,5>decane

Article abstract of DOI:10.1002/hlca.19870700731

In the presence of AlBr3 in CS2 at temperatures below 0 deg C, syn-tricyclo<4.2.1.1^2,5>decane (1) isomerizes exclusively to anti-tricyclo<4.2.1.1^2,5>decane (2) at a higher rate than the latter rearranges to 2-exo,3-exo-trimethylene-8,9,10-trinorbornane (4).However, at temperatures above 0 deg C, the anti isomer 2 isomerizes to 4 faster than 1 to 2 and 4.As a consequence, hydride abstraction occurs at C(3) (->carbocation a, which rearranges to carbocation b (anti skeleton)) in the syn-isomer 1 and more readily at C(9) (->carbocation c) than at C(3) (->carbocation b) in the anti-isomer 2.