Ring-opening reactions of siloxycyclopropanes 1 with SnCl4 take place under mild reaction conditions and site-selectively to give β-trichlorostannyl ketones and aldehydes 3 in high yields. The β-trichlorostannyl ketones and aldehydes thus obtained readily undergo base-induced dehydrotrichlorostannation at room temperature to give the corresponding α-methylene ketones and aldehydes 4. The reactions are quite general for amines, such as pyridine, triethylamine, N,N,N′,N′-tetramethylethylenediamine (TMEDA), and 1,4-diazabicyclo[2.2.2]octane (DABCO), and the yields are good to high. One-pot conversion from siloxycyclopropanes 1 to α-methylene ketones or aldehydes 4 by consecutive treatment of 1 with SnCl4 and TMEDA is also successful. The 1H NMR, 13C NMR, 119Sn NMR, and IR spectral properties of β-stannyl ketones and aldehydes are also reported.