A new spiro{2H-naphtho[2,1-b]pyran-2,2′-2′H-1′-benzothiopyran} giving a near-ir absorption band on UV irradiation

Abstract

Novel 4′-styryl spiro{2H-naphtho[2,1-b]pyran-2,2′-2′H-1′-benzothiopyrans} have been prepared by condensation of 2,4-dimethyl-1-benzothiopyrylium perchiorate (1) with 2-hydroxy-1-naphthaldehyde (3) followed by deprotonation with piperidine which gave the coloured form having an absorption band in the near-IR region on UV irradiation.