28627-77-2Relevant articles and documents
Synthesis and Solvolysis of Bicyclohept-3-en-2-yl, Bicyclohept-2-yl, and 2-Halogenocyclohex-2-en-1-yl Methanesulfonates and p-Nitrobenzoates
Bentley, T. William,Norman, Simon J.,Kemmer, Ralf,Christl, Manfred
, p. 599 - 608 (2007/10/02)
As an extension of previous work bicyclohept-3-en-2-ol (5) was synthesised in four steps from benzvalene and is now much more accessible than by former routes.The 3-bromo derivative 9 of 5 was obtained from bicyclohexene by addition of dibromocarbene and hydrolysis of the resulting dibromide 8. - Methanesulfonates were prepared from 5, 9, 2-norpinanol (7) as well as from 2-bromo- (11a) and 2-chlorocyclohex-2-en-1-ol (11b).Due to its high reactivity, the bicycloheptenyl mesylate 12 could only be characterized by low-temperature NMR spectra.At 20 deg C, 2-norpinyl mesylate (16) rearranged slowly to endo- (endo-17) and exo-2-norbornyl mesylate (exo-17) in the ratio 2:1.The formation of endo-17 was also the major process on treatment of 16 with aqueous ethanol or acetone. - Solvolyses of bicycloheptenyl mesylates 12 and 20 proceed 4-5 times more slowly than solvolyses of corresponding cyclohexenyl mesylates 21c and 21a.The β-bromine substituent deactivates solvolyses of 21a compared with 21c, and 20 compared with 12, by a factor of 2E3.The allylic double bond accelerates solvolyses of 21c compared with cyclohexyl mesylate by a factor of 1E7.However, 12 solvolyses only 100 times faster than norpinyl mesylate 16, showing a 1E5-fold effect due to cyclobutylcarbinyl ring expansion.From solvolysis data the energy difference between the 2-norpinyl and 2-norbornyl cation is estimated to be 16 kcal mol-1, in fair agreement with a recent ab initio calculation. - Key Words: Bicyclohept-3-en-2-ol, synthesis of / Cyclobutylcarbinyl mesylates, solvolysis of / 2-Norpinyl cation / β-Halogen substituent effects on substitution rates / p-Nitrobenzoates, alkyl-oxygen versus acyl-oxygen cleavage
