Synthesis of functionalized 2,3-dihydrothieno[2,3-d]pyrimidin-4(1H)-ones and their recyclization to 2,3-dihydrothieno[3,4-d]pyrimidin-4(1H)-ones

Chemistry of heterocyclic compounds at the Institute of Organic Chemistry, National Academy of Sciences of Ukraine (Review)

“…The first of them involves the principle of the construction of the 1,3-azine ring by a [5+1] heterocyclization mechanism and is based on the reaction of available 2-alkyl(aryl)amino-1-cyano-2-mercapto-acrylamides with carbonyl compounds [91]. The second is based on a new variant of the formation of the heterocyclic ring by a [3+3] cyclocondensation mechanism, which was realized successfully on examples of the reaction of 1-chloroalkyl isocyanates with 1,3-C,N-, 1,3-C,O-, and 1,3-C,S-binucleophilic reagents [91,92]. As a result of the experiments the published data concerning the structure of the products from the condensation of 2-alkyl(aryl)amino-1-cyanacryl-2-mercaptoamides with aldehydes and ketones were rejected, and it was established that they are in fact derivatives of 6-alkyl(aryl)amino-2,3-dihydro-1,3-thiazin-4(1H)-one.…”

“…During heating in acetic acid it was found that they are susceptible to transformation into the isomeric heterocyclic system of 2,3-dihydrothieno [3,4-d]pyrimidin-4-(1H)-one. The effect of temperature and the nature of the substituents on the course of this process was studied in detail [91,92].…”

Chemistry of 1,3-thiazin-4-ones and their derivatives, 1995 - mid-2018

“…The subsequently formed enolate ion 520 then attacked the nitrile, leading to the fused ring 516 (Scheme 163). 39 The formation of compounds 518 had been earlier demonstrated by hydrolysis of 72 with aqueous KOH, which gave the potassium salts of 518 (R 1 = Et, Ph; R 2 = H; R 3 = Ph, 4-NO 2 -C 6 H 4 ; 75-82%). 37…”

“…In another method, 3-alkyl(aryl)amino-2-cyano-3-sulfanylacrylamides 1 reacted with aldehydes and ketones 71, with catalytic TsOH as above, to produce compounds 72 (Scheme 21). 17,[37][38][39][40][41]…”

“…Reaction of 5-cyano-6amino-1,3-thiazin-4-ones 72 with β-ketoalkyl halides 515 and triethylamine gave thienopyrimidone products 516. 39 This was explained by base-promoted Dimroth rearrangement to give an exo sulfur anion 518, which then attacked the alkyl halide 515. The subsequently formed enolate ion 520 then attacked the nitrile, leading to the fused ring 516 (Scheme 163).…”