Trifluoromethylated 2H‐Thiete, 2,3‐Dihydrothiophenes and 3,4‐Dihydro‐2H‐thiopyranes S,S‐Dioxides in [3+2]‐Cycloaddition Reactions with Diazo Compounds and Nitrilimines

Abstract [3+2]‐Cycloaddition reactions of 3‐trifluoromethyl‐2 H ‐thiete 1,1‐dioxide, 4(5)‐trifluoromethyl‐2,3‐dihydrothiophene 1,1‐dioxides and 5(6)‐trifluoromethyl‐3,4‐dihydro‐2 H ‐thiopyrane 1,1‐dioxides with diazomethane proceed with the formation of regioisomeric mixtures of corresponding dihydropyrazole‐fused cycloadducts. Reactions of 3‐trifluoromethyl‐2 H ‐thiete 1,1‐dioxide with ethyl diazoacetate and in situ generated 2,2,2‐trifluorodiazoethane lead to the regioselective formation of pyrazolino‐sultine derivatives via rearrangement of initially formed pyrazoline‐fused thietane 1,1‐dioxides. Treatment of 3‐trifluoromethyl‐2 H ‐thiete 1,1‐dioxide and 4‐trifluoromethyl‐2,3‐dihydro‐thiophene 1,1‐dioxide with in situ generated N ‐phenyl nitrilimines gives rise to dihydropyrazole‐ thietane 1,1‐dioxides and tetrahydrothiophene 1,1‐dioxides, respectively, in a regioselective fashion.