1,4-NAPHTHOQUINONES .24. ON THE DEHALOGEN ATION OF 2- 3-HALOGEN-1,4-NAPHTHOQUINONE DERIVATIVES/

Bu(3)SnH is an effective reagent for the debromination of 2-bromonapht hoquinones but elimination of chlorine with 1c, e.g., only proceeds at 30%. With Et(3)SiH dechlorination does not occur at all. instead, wit h the 5-acetoxy derivatives 1a/1d as starting materials the cyclic ace tales 3a-c are formed as selectively protected juglone derivatives. Th e bromo derivative 3a is obtained only at temp. < 10 degrees and even at room temp. Br-Elimination occurs with low yield of 3b. An especiall y suitable reagent for the debromination of 1a-b leading to the natura l compounds plumbagin (2a) and isoplumbagin (2b) is zinc-silver couple bur Cl-elimination again occurs in traces only.