Synthetic approaches to 3-amino-1,4-naphthoquinone-2-carboxylic acid derivatives and photochemical synthesis of novel 1,4,5,10-tetrahydro-5,10-dioxo-2H-naphth[2,3-d][1,3]oxazine derivatives

Abstract

Synthesis of 3-alkylamino-1,4-naphthoquinone-2-carboxylic acid (2) was attempted. Although 3-(1-piperidinyl)-1,4-naphthoquinone-2-carboxylic acid (2a) was not obtained, probably because of its instability, the esters (18a, b) of 2a could be prepared. 2-Alkylamino-3-hydroxymethyl-1,4-naphthoquinones (9a-g) were photochemically cyclized to the 1,4,5,10-tetrahydro-5,10-2H-naphth[2,3-d][1,3]oxazines (19a-g), containing a novel heterocyclic ring system in moderate yields. Anti-bacterial activity of the prepared compounds was weak or insignificant.