The first example of the Fischer–Hepp type rearrangement in pyrimidines

Abstract

SummaryA N-nitroso moiety can be used for the activation of chloropyrimidines toward a nucleophilic substitution reaction with amines. The subsequent treatment of the obtained products with aq H2SO4 can lead to either N-denitrosation to obtain 4,6-pyrimidinediamines or to a Fischer–Hepp type rearrangement to obtain 5-nitroso-4,6-pyrimidinediamines. It was found that the outcome of the reaction strongly depends on the structure of the pyrimidines. Activation of the pyrimidine ring by three groups with a positive mesomeric effect is crucial for the intramolecular nitroso group migration.

IBD-mediated oxidative cyclization of pyrimidinylhydrazones and concurrent Dimroth rearrangement: Synthesis of [1,2,4]triazolo[1,5-c]pyrimidine derivatives

“…The procedure offers several advantages including good yields, operational simplicity, environmental friendliness and shorter reaction time along with broad substrate scope, which make it a useful and attractive process for the synthesis of structurally diverse triazolopyrimidines. Moreover, the 7-chloro-substitution would allow further manipulations through nucleophilic substitution [ 23 ] and metal-catalyzed cross-coupling reactions, which are under investigation in our group.…”

On the scope of oxidation of tertiary amines: Meisenheimer rearrangements versus Cope elimination in 2-(cyanoethyl)-2-azanorbornanes

“…(±) Methyl 2-(cyanoethyl)-2-azabicyclo[2.2.1]heptane-3-exocarboxylate (5). Following the general Michael addition procedure, to the previously prepared amine 9 were added DIPEA, a catalytic amount of DMAP and acrylonitrile.…”

“…1 Currently, there are many known mechanisms of rearrangement reactions, 2,3 but there are also examples where products are formed through rearrangements difficult to explain. [3][4][5][6][7][8] Nitrogen compounds, such as amines, nitriles or oximes, are relatively prone to rearrangement reactions. Examples of such rearrangements induced by oxidation of tertiary amines are the Meisenheimer rearrangement 3,9 and the Cope elimination.…”

Symmetric 4,6-Dialkyl/arylamino-5-nitropyrimidines: Theoretical Explanation of Why Aminolysis of Alkoxy Groups Is Favoured over Chlorine Aminolysis in Nitro-Activated Pyrimidines.

“…However, under mild conditions, the dialkyl amine disubstituted product 5 was preferentially obtained. This was surprising, as the disubstitution of two chlorine atoms in the reaction of 4,6dichloro-5-nitropyrimidine 1 with alkylamines requires strong conditions 11 . Scheme 1.…”