SYNTHESIS OF ACRYLAMIDINES VIA THE INTRAMOLECULAR AMINO GROUP MIGRATION

Abstract

Ketenimine is a synthetic intermediate that has been applied in wide ranges of reactions. Cu(I) catalyzed cycloaddition reaction of alkyne with sulfonylazide is reported to form ketenimine intermediate which participate in addition reactions with various external nucleophiles e.g. amine, alcohol, water, etc. In the present work, we demonstrate new types of reactions i.e. rearrangements of ketenimines involving a flanking amino group as an internal nucleophile. We report that propargylamine derivatives when reacted with sulfonylazides undergo a 1,3-amino group migration leading to acrylamidines. The methodology allows the formation of acrylamidines even in the presence of competing nucleophiles, such as H2O, alcohol, amine and thiol. We further demonstrate that a flanked amino group also undergoes 1,5- migration when a C=C moiety is introduced between the alkyne and the aminomethylene group. Cis-stereochemistry of these groups around the C=C is important for the rearrangement to proceed.