Synthesis of 1,2,5-oxathiazole-S-oxides by 1,3-dipolar cycloadditions of nitrile oxides to α-oxo sulfines

Abstract

The generation of novel 1,2,5-oxathiazole-S-oxide cycloadducts from cycloaddition of nitrile oxide dipoles with α-oxo sulfines generated in situ from α-diazosulfoxides is reported.

Flow Chemistry for Cycloaddition Reactions

“…The formation of oxathiazoles reported by Maguire, Collins and co‐workers involved a cycloaddition of nitrile oxide dipoles with α‐oxo sulfines generated in situ via the α‐sulfinyl carbenes derived from α‐diazosulfoxides. Thermodynamic isomers were predominant using continuous flow (generation of α‐oxo sulfine by thermolysis) while batch procedure led to the selective formation and isolation of the kinetic isomers (generation of α‐oxo sulfine using rhodium acetate as the catalyst at 0 °C, Scheme ) …”

“…Thermodynamic isomers were predominant using continuous flow (generation of α-oxo sulfine by thermolysis) while batch procedure led to the selective formation and isolation of the kinetic isomers (generation of α-oxo sulfine using rhodium acetate as the catalyst at 0 °C, Scheme 45). [133] A 1,3-dipolar cycloaddition reported by Baumann and Baxendale between a nitrile oxide and a thiourea compound initially generated an unstable 1,4,2-oxathiazoline intermediate that readily rearranged into urea and the desired isothiocyanate product (Scheme 46) Interestingly, the authors found that an immobilized thiourea (QP-TU, or QS-MTU) served as an efficient source of a sulfur atom. Both the solid supported base (SiO 2pyr) and immobilized thiourea species were blended filled into a glass column and the column inserted into a glass heating jacket which was maintained at 50 °C.…”