1,4-Naphthoquinones, XXIV: On the dehalogenation of 2-/3-halogen-1,4-naphthoquinone derivatives

Article abstract of DOI:10.1002/ardp.19953280219

Bu₃SnH is an effective reagent for the debromination of 2-bromonaphthoquinones but elimination of chlorine with 1c, e.g., only proceeds at 30%. With Et₃SiH dechlorination does not occur at all. Instead, with the 5-acetoxy derivatives 1a/1d as starting materials the cyclic acetales 3a-c are formed as selectively protected juglone derivatives. The bromo derivative 3a is obtained only at temp. < 10° and even at room temp. Br-Elimination occurs with low yield of 3b. An especially suitable reagent for the debromination of 1a-b leading to the natural compounds plumbagin (2a) and isoplumbagin (2b) is zinc-silver couple but Cl-elimination again occurs in traces only.