Halocyclization of Substituted 2-(Alkenylthio)pyrimidin-6-ones

The Use of Electrophilic Cyclization for the Preparation of Condensed Heterocycles

“…Thus, the action of PPA or sulfuric acid on allyl derivatives led to the formation of angular thiazolo(imidazolo)pyrimidines 24, 25,28,29,31 while HBr or HCl only protonated the heterocyclic nitrogen with retention of the double bond. 27,33 In addition, the cyclization of 2-allyl(methallyl)sulfanyl-pyrimidin-4(3H)-ones under the action of sulfuric acid or HBr 22,27,32 selectively gave the linear fused isomer, as was shown earlier with analogous 2-allylsulfanylthieno [2,3d]pyrimidin-4(3H)-ones. 37 Cinnamyl derivatives of (di)azinopyrimidines regioselectively annulate six-membered rings under the action of PPA (Scheme 5), but the direction of cyclization strongly depends on the nature of the substituents present in the title pyrimidines: pteridin-4(3H)-one 31 forms a linear condensed system 25, unlike pyrido [2,3-d]( [3,4-d])pyrimidin-4-ones, 28,29 which give angular isomers 26.…”

“…It is noteworthy that the halogenation of 2-(propargylthio)pyrimidin-4-ones 11 22,23 and 4-imino(oxo)-6-propargylthio(amino)pyrazolo [3,4-d]pyrimidines 12 [24][25][26] nonstereoselectively gives the similar angular condensed heterocyclic system 14, albeit the Z-isomer dominates in the reaction mixture (Scheme 3). The use of the sulfuric acid as the electrophile leads to protonation of the more basic nitrogen atom with the formation of linearly fused pyrimidines 15 from thioethers, 25 or angular condensed systems 16 from amino derivatives, 26 whereas HBr only protonates the heterocyclic nitrogen with retention of the triple bond.…”

“…It is remarkable that the regiochemistry of these electrophilic cyclizations is virtually independent of the solvents and conditions, whereas the nature of the unsaturated moiety has a major impact on the direction of the electrophilic cyclization (Scheme 5). Alkenylsulfanyl(amino)substituted pyrido [2,3-d]( [3,4-d])pyrimidin-4(3H)-ones, [28][29][30] pteridin-4(3H)-one, 31 pyrimidin-4(5H)-ones, 22,23,27,[32][33][34] thieno [2,3-d]pyrimidin-4(3H)-ones, 35 and pyrazolo [3,4d]pyrimidines [24][25][26]36 22 were used as the starting materials. Glacial acetic or chloroform at room temperature were used as typical solvents for the halogenation, whilst nitromethane with LiClO 4 as an additive were used for arylsulfenyl chlorination.…”

A convenient synthetic approach to a novel class of aryldifluoromethyl pyrimidine derivatives containing strobilurin motif as insecticidal agents

“…The general synthetic methods for compounds are shown in Scheme 1 and intermediates ( 1, 2, 3, 4, 5 ) according to the related literature [41–43], furthermore intermediates 5a–5h and target compounds are listed in Tables 1 and 2. Representative procedures are given below and reaction yields were not optimized.…”

Condensation of S-Substituted 6-Amino-2-Thiouracils with Benzaldehydes

“…Органилсульфиды 1a-d получены нами в водно-спиртовой среде в присутствии щелочи по методике, описанной в работе [19]. В литературе алкилированием 6-амино-2-тиоурацила получены различные S-замещенные производные, в том числе пропаргилсульфид 1a [19], аллилсульфид 1b [19,20], металлилсульфид 1c [19,20] и бензилсульфид 1d [18].…”