Photocyclisation of 3-alkoxy-6-chloro-2-(3-methylthiophen-2-yl)-4H-chromen-4-ones

Photocyclisation of 3-alkoxy-6-chloro-2-(3-methylthiophen-2-yl)-4H -chromen-4-ones in methanol lead to the formation of tetracyclic compounds through H-abstraction is described.

Photocyclisation of 3-alkoxy-6-chloro-2-(3-methylthiophen-2-yl)-4H -chromen-4-ones in methanol with pyrex filtered UV-light lead to the formation of tetracyclic compounds through intramolecular γ-hydrogen abstraction. The methyl group on the thiophenyl ring does not interfere in the photocyclisation although it does effect the product formation.