Synthesis of bridgehead-substituted bicyclo[2.2.1]heptanes by radical cyclization
摘要:
A kinetic investigation shows that the rate of cyclization (k(C)) of the (4-methylenecyclohexyl)methyl radical 3 at 25-degrees-C is 4.4 x 10(2) s-1, which is considerably slower than that (2.3 x 10(5) s-1) of the parent 5-hexenyl radical. The energy of activation for the process 3 - 4 is 12.8 kcal mol-1, which is in excellent agreement with theoretical values derived from force-field calculations. Ring-closure of appropriately substituted (4-methylenecyclohexyl)methyl radical precursors allows the synthesis of bicyclo[2.2.1]heptyl systems with useful functionality at the bridgehead to be achieved readily and in high yield. An interesting example is given of the application of an iodine-atom-transfer cyclization to the synthesis of a bicyclo[2.2.1]heptane functionalized at C7 and C1.
Synthesis of bridgehead-substituted bicyclo[2.2.1]heptanes by radical cyclization
摘要:
A kinetic investigation shows that the rate of cyclization (k(C)) of the (4-methylenecyclohexyl)methyl radical 3 at 25-degrees-C is 4.4 x 10(2) s-1, which is considerably slower than that (2.3 x 10(5) s-1) of the parent 5-hexenyl radical. The energy of activation for the process 3 - 4 is 12.8 kcal mol-1, which is in excellent agreement with theoretical values derived from force-field calculations. Ring-closure of appropriately substituted (4-methylenecyclohexyl)methyl radical precursors allows the synthesis of bicyclo[2.2.1]heptyl systems with useful functionality at the bridgehead to be achieved readily and in high yield. An interesting example is given of the application of an iodine-atom-transfer cyclization to the synthesis of a bicyclo[2.2.1]heptane functionalized at C7 and C1.