Synthesis of Functionalized 4-Methylenetetrahydropyrans by Oxidative Activation of Cinnamyl or Benzyl Ethers

Oxidative activation of benzyl or cinnamyl ether bearing allylsilane derivatives using a catalytic amount of DDQ and 2 equivalents of CAN in the presence of PPTS provided functionalized 4-methylenetetrahydropyrans in good yields and excellent diastereoselectivity. The reaction could be applied to the synthesis of a variety of substituted tetrahydropyran derivatives.