A selective synthesis of hindered 1-adamantyl t-alkyl ethers

The S-N reactions of t-alkyl alcohols with l-adamantyl methanesulfonate and amines(molar ratio 10/1/1) were carried out at 80 -100 degrees C under a nitrogen atmosphere. The corresponding products were obtained in 59 - 94% yields, i.e., l-adamantyl t-butyl ether (90%), l-adamantyl t-pentyl ether (86%), 1-adamantyl 1,1-diethylpropyl ether (82%), l-adamantyl 1,1-dipropylbutyl ether (59%), l-adamantyl 1-methoxycarbonyl-1-methylethyl ether (73%), l-adamantyl l-methyl-l-phenylethyl ether (71%), l-adamantyl 1,1-dimethyl-2-propenyl ether (90%), and l-adamantyl 1,1-dimethyl-2-propynyl ether (94%). In spite of the steric hindrance of t-alkyl alcohol and l-adamantyl substrate, the yields of the ethers were good to excellent. However, l-adamantyl iodide was much less reactive than l-adamantyl methanesulfonate even under severe conditions. The electronic effect of the functional group of t-alkyl alcohol was also exhibited. The optimum reaction conditions were examined, and the reaction mechanism was proposed.