A new route to 1,4-naphthoquinones

We have found that benzylisoquinolines 6 are an attractive synthetic alternative to ketoacids 4 for the preparation of benzofuranonaphthoquinones and indolonaphthoquinones because:

(i) They can be easily prepared according to the Bischler-Napieralski protocol.

Scheme 3

(ii) N-Methylbenzylisoquinolinium derivatives 7 can be directly transformed into phenylnaphthols 8 when treated with sodium hydroxide.

Scheme 4

(iii) Transformation of naphthols 8 into napthoquinones 5 can be achieved as follows:

Scheme 5

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