Ring-opening reactions of cyclic ethers with diiodo- and dibromodimethylsilane equivalents

Ring-opening halosilation of cyclic ethers with reagents of (Me2N)2SiMe2/4MeI (1a) and (Me2N)2SiMe2/4allylBr (1b) was studied. Tetrahydrofuran and cyclohexene oxide reacted with 1a and 1b to give ring-opened di(haloalkoxy)dimethylsilanes in good yield. With less strained tetrahydropyran, however, only reagent 1a gave the ring-opened product. Reactions of reagents 1a and 1b with propylene oxide also proceeded smoothly, although the regioselectivity was rather low. When similar reactions were carried out with (Me2N)2SiMe2/2MeI (2a) and (Me2N)2SiMe2/2allylBr (2b) in a ratio of cyclic ethers/2a or 2b = 1/1, the corresponding 1:1 adducts were obtained.