G. Palui, L. M. Sitkina, A. D. Dubonosov
Apr 1, 1988
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Journal
Chemistry of Heterocyclic Compounds
Abstract
O- and N-Acylated alkylimines of 3-hydroxybenzo[b]thiophene-2-carbaldehyde and 3-hydroxy-1-methylindole-2-carbaldehyde were synthesized. Their Z → E isomerizations and N→O-acyl photo- and thermotransformations were investigated by means of electronic and IR spectroscopy. On irradiation N-acyl-N-methyl(or benzyl)amino-methylene derivatives of benzo[b]thiophen-3-one and 1-methylindol-3-one undergo only Z → E isomerization. The introduction of bulkier alkyl substituants (isopropyl, cyclohexyl) relative to the amino nitrogen atom increases the stability of the O-acyl isomers and their conjugate acids and leads to irreversible photoinitiated or acid-catalyzed N → O-acyl rearrangements. Exclusively the O-acyl isomer is realized for compounds with the most bulky N-tert-butyl substituent.