Synthesis, study of the structure, and modification of the products of the reaction of 4-aryl-4-oxobut-2-enoic acids wit
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Synthesis, study of the structure, and modification of the products of the reaction of 4-aryl-4-oxobut-2-enoic acids with thiourea Nadezhda N. Kolos1*, Nikolai V. Nazarenko1, Svetlana V. Shishkina1,2, Andrey O. Doroshenko1, Elena G. Shvets1, Maksim A. Kolosov1, Fedor G. Yaremenko2 1
V. N. Karazin Kharkiv National University, 4 Svobody Sq., Kharkiv 61022, Ukraine; е-mail: [email protected] 2 State Scientific Institution '"'Institute for Single Crystals'', National Academy of Sciences of Ukraine, 60 Nauky Ave., Kharkiv 61001, Ukraine Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(9), 1202–1209
Submitted June 1, 2020 Accepted August 10, 2020
A number of previously undescribed derivatives of 2-amino-5-(2-aryl-2-oxoethyl)thiazol-4(5H)-one containing electron-donating substituents in the aromatic ring were synthesized by the reaction of (E)-4-aryl-4-oxobut-2-enoic acids with thiourea. Reduction of the reaction products with NaBH4 yielded diastereomeric alcohols, whereas bromination in AcOH was accompanied by elimination of HBr and the formation of (Z)-2-amino-5-(2-aryl-2-oxoethylidene)thiazol-4(5H)-ones. Keywords: 2-amino-5-(2-aryl-2-oxoethyl)thiazol-4(5H)-ones, 4-aryl-4-oxobut-2-enoic acids, thiourea, cyclocondensation, oxidative bromination, reduction.
Derivatives of thiazolidin-4-ones exhibit various physiological activity:1–3 analgesic and anti-inflammatory drugs,4–6 fungicides,7 inhibitors of cyclooxygenase-2,8 anticancer and antiviral agents2,9,10 were found among them. Synthetic approaches to 2-amino(imino)thiazolidin4-ones are based, as a rule, on the reactions of thiourea and its derivatives with bielectrophilic reagents.4,7,11–14 Thus, the reaction of 4-aryl-4-oxobut-2-enoic acids with thioureas is a very convenient method for the formation of the thiazolidine ring.15–20 Despite the fact that cyclocondensation of 3-benzoylacrylic acid with thiourea was first carried out as early as in 1947,15 the structure of the molecules of the resulting compounds has been a subject of discussion until recently. Thus, the authors of studies describing the formation of thiazol-4(5Н)-ones A in the reactions of 3-aroylacrylic acids with thioureas by heating under reflux in EtOH with additions of catalytic amounts of AcOH (Fig. 1)16,17 postulate the existence of the keto-enol equilibrium with the participation of the endocyclic carbonyl group. The formation of imino form B has been described elsewhere,18–20 and the imino form becomes the only one 0009-3122/20/56(9)-1202©2020 Springer Science+Business Media, LLC
possible when N,N'-disubstituted thioureas are used in such condensations.21 At the same time, heating the starting reagents in AcOH under reflux leads to tetrahydropyrimidine-2-thione22 or, when the reaction is carried out in MeOH in the presence of EtONa, to its aromatized analog C.23 Data from early studies,24,25 the authors of which postulated the formation of thiohydantoins D, have been convincingly refuted in later studies. NH
NH2 O
S
O
N
S
NH
Ar
Ar A O
O
B
OH
S O
NH Ar
N C
O
HN
N
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