Abstract
A high-yielding method for the synthesis of 2H-1,3,5-oxadiazines by rhodium(II)- or copper(II)-catalyzed reaction of 1,2,4-oxadiazoles
with α-diazo esters has been developed. The reaction proceeds via attack of the metallocarbenoid
on the oxadiazole N2 atom followed by ring opening/1,6-electrocyclization and enables
the introduction of alkyl, aryl, oxy, and amino substituents into the 6-position and
electron-withdrawing groups into the 2-position of 1,3,5-oxadiazine. The N2-attack
and the N4-attack of the carbenoid cause different oxadiazole ring openings, which
are controlled by the substitution at C5. The presence of a substituent at this position
is a prerequisite for the N2-attack to occur, leading to the formation of 1,3,5-oxadiazines.
Key words
diazo compounds - oxadiazoles - oxadiazines - rhodium - catalysis - carbenoids
