One-pot synthesis of benzoxazoles via the metal-free ortho-C–H functionalization of phenols with nitroalkanes

Abstract

PPA-activated nitroalkanes are employed in the design of a one-pot cascade transformation involvingortho-C–H functionalization, by Beckman rearrangement, and condensation to produce benzoxazoles and benzobisoxazoles directly from phenols.

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

“…It was demonstrated that upon heating in polyphosphoric acid, the nitroalkanes 1 convert into the phosphorylated nitronates 2 , which exhibit strong electrophilic properties. This allowed for the employment of these species in reactions wherein electron-rich arenes serve as carbon-based nucleophilies [ 38 – 40 ]. It was also discovered that the nucleophilic amines 3 can be successfully employed in this type of transformations as well, providing the amidinium intermediates 4 , which are susceptible to a variety of subsequent cyclizations.…”

Electrophilic alkylation of arenes with 5-bromopyrimidine en route to 4-aryl-5-alkynylpyrimidines

“…In recent years, our group was interested in designing novel acid-mediated multistep cascade transformations targeting material science and medicinal chemistry applications. [19][20][21][22][23] In particular, an unusual annulation reaction was demonstrated, involving perimidines 7 and pyrimidines 8 and leading to the formation of 1,3-diazapyrenes 9 (Scheme 2). 24 It was also shown that unlike most other pyrimidines, 5-bromopyrimidine 10 did not react according to this general scheme, forming monoalkylation products 11 instead (Scheme 2).…”

Electrophilically activated nitroalkanes in reaction with aliphatic diamines en route to imidazolines

“…This unusual species can be used to design a number of one-pot multi-step transformations involving various carbon-based nucleophiles. [17][18][19] The utilization of nucleophilic amines was also demonstrated. [20][21][22][23][24] Mechanistically, the latter process is related to the classical Nef reaction, [25][26][27] employing aniline [20][21][22][23] or hydrazine 24 species 8 instead of water.…”