Vilsmeier–Haack formylation of acetonitrile revisited: Synthesis of novel pyrazolo[1,5‐a]pyrimidines and triazolo[1,5‐a]pyrimidine

Abstract

in Wiley InterScience (www.interscience.wiley.com).Vilsmeier-Haack formylation of acetonitrile using dimethylformamide and phosphorus oxychloride leading to a novel intermediate, N-((E)-3-(dimethylamino)-2-formylacryloyl)formamidine 2 and its utility in the synthesis of pyrimidine-fused heterocycles such as pyrazolo[1,5-a]pyrimidines and triazolo [1,5-a]pyrimidine is reported.

Heterocyclizations of β-alkoxy, β-diaminoalkyl, and related β-functionalized enones (enals) with NCN-binucleophiles

“…A wide range of β-enaminals bearing an α-substituent have been reported, including compounds with alkyl 10 [40,44,45], cycloalkyl 11 [46], nitrile 12 [47][48][49][50][51], imide 13 [52], ester groups 14 [38], chorine [53], and other moieties (Scheme 5). Formyldiene 15 was used as a versatile reagent for the synthesis of a series of 5-vinylpyrimidines [54].…”

“…The simplest open-chain enones have been widely studied in these reactions and used for the preparation of fused pyrimidines by reactions with aminoheterocycles. Starting from the reaction of ethyl 3-ethoxyacrylate with ethyl 5-amino-1H-pyrazole-4-carboxylate [194,195], the scope of known transformations included reaction of the simplest derivative 8 [196] or 3-(dimethylamino)-N,2diformylacrylamide 14 [52] (Scheme 31). In turn, most of the known transformations relied on using enones derived from ketoesters 39 (Scheme 32) [197][198][199][200][201][202][203] that were subjected to heterocylizations with (3)5-aminopyrazoles (mostly substituted by alkyl, aryl, halogen, nitrile and nitro groups), or diazo diaminopyrazoles [204,205].…”