Formylnitroenamines: useful building blocks for nitrated pyridones and aminopyridines with functional groups

Abstract

beta-formyl-beta-nitroenamines possess both an electrophilic formyl group and a nucleophilic amino group and, therefore, serve as C3N1 building blocks having a nitro group to afford nitropyridones and aminonitropyridines with a functional group at the 3-position. Upon treatment with malonic acid derivatives or beta-keto esters, nitropyridones were obtained, whereas reactions with functionalized acetonitriles afford aminonitropyridines, via a formal transfer of an alkyl group from the ring nitrogen to the imino group. These procedures provide practical and useful methods for preparation of heterocycles with a nitro group.

Synthesis of N‐Bridged 6,8‐Dinitrotriazolo[1,5‐a]pyridines

“…It is well‐known that such Dimroth‐type process can be accomplished by heating with acid or base and is facilitated in case of electron‐withdrawing groups introduced into pyridine ring ,. In some cases the rearrangement of pyridine or pyrimidine derivatives occurs under relatively mild conditions, however, in the presence of nucleophiles, such as H 2 O or NH 3 . We found that this interconversion proceeds at room temperature ( 3 f , Scheme 6 and m , Scheme ) as well as on heating in POCl 3 (106 °C, method A ) or in acetic acid (118 °C, method B ).…”

A one‐pot synthesis of the 1‐benzopyrano[2,3‐b]pyridine moiety from 2‐(alkyl/arylamino)‐4‐oxo‐4H‐1‐benzopyran‐3‐carbaldehyde

“…However, on heating under reflux in ordinary CHCl 3 or benzene in the absence of silica gel, compound 12 failed to show any change. In an earlier report [17], b-allylamino-2-nitroacrolein was made to react with malononitrile and was supposed to (3)''] obtained from the reaction mixture of 3 (R 1 ¼ H, R 2 ¼ Ph) and ethyl cyanoacetate revealed that there was more than one product (TLC). However, chromatographic separation yielded only 11a in moderate yield.…”

“…Recently, diethyl 1-benzopyrano [2,3-b]pyridine-2,3-dicarboxylate has been synthesized from 3 and diethyl acetylenedicarboxylate in the presence of Ph 3 P [16]. Synthesis of 2-pyridone moiety having ester or carbamoyl functionality at its 3-positions from b-formyl-bnitroenamine has recently been reported [17].…”

Synthesis of 4-Substituted 3,5-Dinitro-1,4-dihydropyridines by the Self-Condensation of β-Formyl-β-nitroenamine

“…We have reported that formylnitroenamines 1 serve as a double electrophilic C3 unit having a nitro group to afford nitrated diazoles, isoxazole, pyrimidines, diazepines, phenols upon treatment with dinucleophiles such as hydrazines, hydroxylamine, guanidines, 1,2-diaminoethanes, and ketones, respectively. Formylnitroenamines 1 are also employed as the C3N1 building blocks, and multiply functionalized nitropyridones and aminonitropyridines are readily prepared under mild conditions . In the present work, new reactivity of 1 , self-condensation leading to hitherto unknown 3,5-dinitro-1,4-dihydropyridines (DNDHPs), upon treatment with a Brønsted acid, is demonstrated.…”