Sulfuric Acid → 1,2-Naphthoquinone

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Reaction Steps

The process shown in Scheme 2 can be used for the preparation of compounds in Formula II, III and IV when R7 is not hydrogen and X is oxygen from same starting material 1-1 as shown in Scheme 1. The reaction of 2-hydroxy-1,4-naphthoquinone 1-1 with the appropriate allylbromide gives 2-allyloxy-1,4-naphthoquinone 2-2. Rearrangement of 2-2 in ethanol afford 2-hydroxy-3-allyl-1,4-naphthoquinone 2-3, which can be cyclized by sulfuric acid treatment to form orthonaphthoquinone 2-4. Oxidation of 2-4 with n-bromosuccinimide and lead tetraacetate gives 3-acetoxy-orthonaphthoquinone 2-5. Hydrochloric acid treatment of compound 2-5 gives 2-alkyl (or aryl)-3-alkyl (or aryl)-naphtha[2,3-b]furan-4,9-dione 2-6.

Provenance & Evidence