M. Tada et al., REACTION OF (3-FURYLMETHYL)COBALOXIME WITH DIENOPHILES - VARIABLE-MODE OF THE REACTION BY THE TYPE OF DIENOPHILES, Journal of organic chemistry, 60(3), 1995, pp. 550-553
(3-Furylmethyl)cobaloxime reacts with dienophiles in three reaction mo
des: (a) a 1,4-addition with N-phenylmaleimide and maleic anhydride, (
b) a 1,4-cycloaddition and concomitant 1,3-migration of the cobaloxime
moiety with dimethyl acetylenedicarboxylate, and (c) a formal aromati
c substitution on the furan ring with active carbonyl compounds such a
s 2-oxomalonate, hexafluoroacetone, and 2-oxoaldehydes. The adducts fr
om 2-aryl-2-oxoacetaldehyde easily loose the cobaloxime moiety on heat
ing and give 2-(2-aryl-2-oxoacetyl)-3-methylfuran.