Reactions of methyl 2-aryl-2H-azirine-3-carboxylates with nucleophiles

Reactions of the methyl 2-aryl-2H-azirine-3-carboxylates 1a and 1b with nucleophiles are described. Thiols add to the C=N bond to give aziridines 4-6. Propargyl alcohol similarly gives the aziridine 7. Primary and secondary aliphatic amines react with the azirines to give methyl 3-aminoacrylates 8-12. 4-Cyclohexen-1-ylmorpholine and 1-cyclopenten-1-ylpyrrolidine react with the azirine 1a to give products formulated as the aziridine 13 and the vinylidenecyclopentanone 14, respectively, in contrast to previously reported reactions of enamines with azirines from which pyrroles were isolated, Acetylacetone gives a pyrrole-3-carboxylate 15 in low yield with the azirine 1a. All these products have been rationalised by invoking initial addition of the nucleophile to the C=N bond of the azirine. The tetrahydrofuran-2-yl radical also adds to the C=N bond of the azirine la, giving the aziridine 16 as a single diastereoisomer. X-Ray crystal structures of methyl (E)-3-amino-3-(2,6-dichlorophenyl)-2-morpholin-4-ylpropenoate 8 and of methyl 3-(2,6-dichlorophenyl)-2-(tetrahydrofuran-2-yl)aziridine-2-carboxylate 16 are reported.