CAN induced double ether ring formation: synthesis of trans- and cis-fusedtricyclic ethers from 3-oxabicyclo[3.1.0]hexyl sulfides

CAN oxidation of 3-oxabicyclo[3.1.0]hexy sulfides 4 and 5 possessing two hy droxy groups in the C-2 and C-4 side chains promoted a double ether ring fo rmation along with a cleavage of the most substituted cyclopropyl bond to g ive tricyclic ketal adducts 8 and 10, which were converted to trans- and ci s-fused tricyclic ethers 9 and 11 with high or moderate stereoselectivity b y a TMSOTf-mediated trialkylsilane reduction.