Photochemical transformations of protonated phenols. A one-step synthesis of umbellulone from thymol

P Baeckstroem, U Jacobsson, B Koutek…

Index: Baeckstroem, Peter; Jacobsson, Ulla; Koutek, Bohumir; Norin, Torbjoern Journal of Organic Chemistry, 1985 , vol. 50, # 20 p. 3728 - 3732

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Citation Number: 18

Abstract

UV irradiation of thymol (7) at 254 or 300 nm in trifluoromethanesulfonic acid affords ten products, eight of which have been isolated and characterized. Four competitive processes are suggested to be operating in the formation of the photoproducts:(i) regioselective type A rearrangement leading to umbellulone (8, about lo%),(ii) formal C2-C3 migration by type A rearrangement and ring opening which affords the principal product, 3-isopropyl-5- ...

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