Rearrangements of Some Bicyclic Systems

[摘要] This thesis deals with some aspects of the rearrangements of bridged bicyclic systems. The acetolysis of erythroxylol B toluene-p-sulphonate (31, R=OTs) has been studied. (Chapter 1.). The 1-bicyclo (3,2,1) octylcarbinyl system rearranges with ring expansion to the substituted bicyclo (3,3,1)-and bicyclo (3,2,2) nonyl derivatives (38 and 33, R=OAc). Dihydroerythroxylol B tosylate (44, R=OTs) rearranges in an analogous manner. It is proposed that these reactions may involve bridged carbonium ions. In an attempt to interconvert the known tetracyclic diterpenes, kaurene (51) has been treated with formic acid (Chapter 2.). The three products isolated are all stachane formates (56, 58 and 60, R=OF) the substituent being located at C-15, C-16 or C-12 in the stachane skeleton. The 12-formate arises from a net 1,3-hydride shift from C-12 to C-16. The buffered acetolysis of exo-bicyclo (3,2,1) octane-6-toluene-p-sulphonate (93, R=OTs) has been found to give exo-2-bicyclo (3,2,1) octyl acetate, 40% (100, R=OAc) 2-bicyclo (2,2,2) octyl acetate, 44% (101, R=OAc) and exo-6-bicyclo (3,2,1) octyl acetate, 16% (93, R=OAc), whereas the corresponding endo-6-isomer gave (100, R=OAc) 19% (101, R=OAc), 21% and (93, R=OAc) 60% (Chapter 3.). The significance of these results is discussed in terms of a 4,6-hydride shift in the bicyclo (3,2,1) octane skeleton. Bridged cations (or equivalents) are postulated to be involved in these reactions. The rates of solvolysis of these toluene-p-sulphonates have been determined. A possible pi-route to the 6-bicyclo (3,2,1) octyl cation has been examined by solvolysis of 3-3cyclopentenyl propyl toluene-p-sulphonate (131, X=OTs) in acetic acid (Chapter 4.). Using either sodium acetate or urea as a buffer no bicyclic acetates were detected from the reaction the sole product being the corresponding primary acetate. The reduction of syn-bicyclo (2,2,2) oct-5-en-2-yl toluene-p-sulphonate (143, X=OTs) with lithium aluminium hydride in refluxing diethyl ether has been found to give bicyclo (3,2,1) oct-2-ene (146) (Chapter 5.). The corresponding anti-toluene-p-sulphonate (144, X=OTs) under identical conditions also gave a major product with a modified skeleton, namely tricyclo (3,2,1,0 2,7)-octane (147). Further examination of the reaction using deuterium labelled compounds led to the conclusion that long-lived ionic intermediates are not involved.

[发布机构] University:University of Glasgow

[关键词] Organic chemistry