The products of hetero-Diels-Alder reactions (sultines) and cheletropic addition reactions (sulfolenes) between 1,3-dienes and sulfur dioxide can be distinguished by their 17O NMR shifts. Experimental data have been collected for derivatives of 3,6-dihydro-1,2-oxathiin-2-oxide and of 2,5-dihydrothiophene-1,1-dioxide. This data was then compared with that calculated by the gauge independent atomic orbital (GIAO) method at the HF/6-31 + G(d,p) and HF/6-311 + G(3df, 2p) levels of theory with geometries optimized by MP2/6-31G(d) calculations. GIAO-MBPT(2) calculations were also performed with the 6-31 + G(d,p) basis set. The adduct between (E)-1-methoxybutadiene and SO2 is sulfolene 3, the ozonolysis of which in SO2 followed by work-up with ethanol provided (2RS,3SR,6SR)-(31), (2RS,3RS,6SR)-(32), and (2RS,3RS, 6RS)-2,6-diethoxy-3-methoxy-1,4-oxathiane-4,4-dioxide (33). Single-crystal X-ray diffraction studies are reported for 32 and 33. Ozonolysis of the hetero-Diels-Alder adduct of SO2 with 1,2-dimethylidenecyclohexane produced 4,9-dioxo-1,2-oxathiacyclodecane-2-oxide (34), the first member of a new class of sulfur heterocycles.