[40028-33-9] · C4H6N2O4S · 2-Methoxy-6-methyl-1,4,3,5-oxathiadiazine 4,4-Dioxide · (MW 178.19)
(reagent for in situ generation of methyl N-sulfonylurethane; provides lower concentrations and higher reaction temperatures than direct formation)
Physical Data: mp 102-103 °C.
Preparative Method: reaction of Methoxycarbonylsulfamoyl Chloride with Sodium Hydride in acetonitrile1 leads to the title reagent (1).
Methyl N-sulfonylurethane (2) has demonstrated a high degree of electrophilic reactivity in cycloadditions with a variety of alkenes to provide 2-methoxycarbonyl-1,2-thiazetidines (3) and 2,3-dihydro-6-methoxy-1,4,5-oxathiazines (4) (eq 1).2 Additions to alkynes proceed to give exclusively the 1,4,3-oxathiazine (5) (eq 2).
This unstable reagent has been prepared by two methods. First, by direct dehalogenation of methoxycarbonylsulfamoyl chloride using sodium hydride.2 The second involves the in situ fragmentation of the title reagent (1).3 This reagent apparently undergoes a thermal [2 + 4] cycloreversion above 30 °C. Reaction of (1) with a variety of alkenes provides identical products to those reported with (2). This second method has the advantage that longer reaction times and higher temperatures are possible. Cycloadducts were obtained from otherwise unreactive alkenes such as cis-stilbene and cyclooctatetraene, employing this method.
The two methods give differing results, however, in the addition to ynamines (6).4 In this case the low-temperature generation provided the expected product (7), while the cycloreversion method led to the new product (8) (eqs 3 and 4).
Paul M. Herrinton
The Upjohn Company, Kalamazoo, MI, USA