Photochemistry of 3-alkoxy chromones : Photocyclisation of 3-benzyloxy-6-chloro-2-(1' -methyl-2' -phenylvinyl)-4-oxo-4H-1-benzopyran

Department of Chemistry, Kurukshetra University, Kurukshetra-136 119, Haryana, India E-mail : rckamboj@rediffmail.com Fax: 91-1744-238277 Manuscript received 31 December 2007. accepted 6 May 2008 Photocyclisation of 3-benzyloxy-6-chloro-2-(11 -methyl-21 -phenylvinyl)-4-oxo-4H-1-benzopyran with pyrex filtered UV light to yield linear tricyclic pyranopyrone and angular fused tetracyclic compound is described. The product formation occurred via cyclisation of 1,4-biradical produced through H-abstraction by C=O group and conrotatory 6xcelectrocyclisation