Synthesis of Functionalized Indole-1-oxide Derivatives via Cascade Reactions of Allenynes and ᵗBuONO
2019
He, Yan | Feng, Tian | Fan, Xuesen
This paper presents a novel access to 5-oxo-2H-benzo[g]indole-1-oxides/functionalized naphthalene-1,2-diones via the cascade reaction of allenynes with alcohols/amines and ᵗBuONO without using any catalyst. Mechanistically, the formation of 5-oxo-2H-benzo[g]indole-1-oxides involves a cascade process combining [2 + 2] cycloaddition, 1,6-addition, and ring expansion of the in situ formed cyclobutene intermediate. The construction of naphthalene-1,2-diones should undergo a ring-opening pathway. Moreover, the utility of benzoindole-1-oxides was demonstrated by their easy conversion into pharmaceutically significant 1H-benzo[g]indol-5-ol derivatives.
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