Search

PPA-activated nitroalkanes are employed in the design of a one-pot cascade transformation involving metal-free and oxidant-free direct ortho-C–H functionalization, followed by Beckman rearrangement and intramolecular cyclocondensation to produce benzoxazoles and benzobisoxazoles directly from easily available phenols.

The reaction of phenylenediamines and 2-aminophenols (I) with nitroalkanes (II) in PPA leads to desired benzimidazoles and benzoxazoles (III) in high yields, whilst the reaction with 2-nitro-1-phenylethan-1-one (IV) affords unexpected 2-phenyl substituted products.

The title compounds are obtained by a novel acid-mediated cascade transformation via the ANRORC (addition of nucleophile, ring opening, and ring closure) mechanism.

A modular approach to 3-substituted 2-quinolones via a cascade annulation reaction between 4-nitroketones and hydrazines has been developed.

Nitration of acylperimidines (I) using NaNO2 in formic acid gives predominantly the 6(7)-nitro-derivatives (II), which can be smoothly transformed into tetraazapyrenes (IV) via a Schmidt Reaction, or triazacyclopentaphenalenes (V) via simple Zn-reduction.

3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone.

Three of the title compounds are synthesized in moderate yields by reaction of naphthotriazine (I) with β-nitrostyrenes.

Previously unknown title compounds are smoothly synthesized by treatment of perimidines (I) with β-nitrostyrene via in situ generated oximes and subsequent Beckmann rearrangement.