Addition reactions of 2-amino-4-methoxypenta-2,4-dienenitrile with electrophiles containing electron-deficient multiple bonds

Abstract

The title compound 1 underwent an insertion reaction with dichlorocarbene selectively at the C-4 double bond. The [4 + 2]cycloadditions of 1 with benzoquinone and naphthoquinone proceeded by subsequent dehydrocyanation and oxidative aromatization under mild conditions to give the diarylamines 6 and 7. The cycloaddition of 1 and N-phenylmaleimide in a sealed tube proceeded with reinsertion of the cyanide ion to give the diarylamine 8. The homologation of 1 with chlorosulfonyl isocyanate (CSI) and tetracyanoethylene (TCNE), giving the dienoate 9 and the triene 10, was unusual compared with commonly observed [2 + 2]cycloadditions of CSI and TCNE. The reaction of 1 with dimethyl acetylenedicarboxylate proceeded via an intermediate cyclobutene and tandem ring-opening afforded the triene 11. The reaction of 1 with ethyl propiolate produced two diarylamines 12a and 12b. Formation of 12a might involve cyanide reinsertion on the intermediate derived from the [4 + 2]cycloaddition, whereas an opening of the [2 + 2] intermediate followed by an electrocyclization would yield the isomer 12b.