Rational design of an efficient one-pot synthesis of 6H-pyrrolo[2,3,4-gh]perimidines in polyphosphoric acid

Abstract

Several highly efficient one-pot synthetic protocols were developed, enabling polyphosphoric acid-activated nitroalkanes to act as electrophiles in reactions with aminonapthalenes.

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

“…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. This approach opens up a novel avenue by which to access the benzoxazoles 5 [ 40 ], benzimidazoles 6 [ 40 – 41 ], diazines 7 [ 42 – 43 ], or imidazolines 8 ( Scheme 1 ) [ 44 ]. We have also shown that a nucleophilic attack on the phosphorylated nitronate species 2 can be carried out with the participation of N -acylhydrazides or thiosemicarbazides to afford the 1,3,4-oxadiazoles 9 [ 45 ] and the 1,3,4-thiadiazoles 10 [ 46 ], respectively ( Scheme 1 ).…”

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

“…[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. It was proposed, that this reaction initially provides imidinium ion 9, that can be further employed as a convenient building block for the synthesis of heterocyclic Scheme 1 Formation of imidazolines.…”

“…compounds: benzoxazoles 10, benzimidazoles 11, diazines 12-13, [20][21][22][23] and oxadiazoles 14 (ref. 24) (Scheme 2).…”

Electrophilically Activated Nitroalkanes in Reactions With Carbon Based Nucleophiles

“…Related processes, featuring nucleophilic secondary nucleophilic attack with nitrogen atom to form pyrimidine ring was also reported (Aksenov et al, 2016).…”