Iron(II)‐catalyzed Oxidative Coupling of Vicinal Diols and 2‐Amino‐1,4‐naphthoquinone for the Synthesis of Pyrrolonaphthoquinones and Furanonaphthoquinones

Abstract

AbstractDirect oxidative coupling of vicinal diols with 2‐aminonaphthoquinones has been studied for the selective synthesis of benzo[f]indole‐4,9‐diones at a moderate temperature. In the presence of an environmentally benign iron catalyst, the vicinal diols were oxidized to α‐hydroxy carbonyl compounds. Subsequently, 2‐amino naphthoquinone reacted with the resultant α‐hydroxy carbonyl compound through tandem N−C and C−C bond formation to afford a vast range of pyrrolonaphthoquinones in remarkable yield. Interestingly, when the 1,2‐propanediol was used, the secondary alcohol group was oxidized preferably by resulting in the 2‐methyl pyrrolonaphthoquinones as the major regioisomer. The synthetic utility of the current strategy was extended for one‐step delivery of natural products, such as 3‐methyl‐1H‐benzo[f]indole‐4,9‐dione (a secondary metabolite isolated from Goniothalamus tapis Miq. with anti‐PAF activity), antibiotic utahmycin B (3‐methyl‐1H‐benzo[f]indole‐4,9‐dione), cytotoxic avicequinone B and anti‐viral FNQ3 (2‐methyl‐naphtho[2,3‐b]furan‐4,9‐dione).