Ferrocenyltetrahydropyrimidin-2-ones were prepared by reactions of linear and cyclic a,b-unsaturated ketones of the ferrocene series with urea in i-PrOH in the presence of t-BuOK. The structures of the compounds prepared were studied by 1 H and 13 C NMR and IR spectroscopy, and also by single crystal X-ray diffraction.Urea, thiourea, and their derivatives are used in synthesis of pyrimidine derivatives, which are components of many biologically active substances and nucleic acids [1]. In the metallocene series, the reactions of thiourea [23 6] and phenylthiourea [6] with ferrocenyl-substituted chalcones have been reported, but there is no unambiguous opinion on the structure of the products. The reactions were performed in alcohol in the presence of sodium alcoholates with refluxing [3,4,6] or under ultrasonic treatment [5]. The products of condensation with thiourea were identified as tetrahydropyrimidinethiones I with the C=C double bond at the 4,5 position, and the products of condensation with phenylthiourea, as tetrahydropyrimidinethiones II with the C=C double bond at the 3,4 position (Scheme 1). Scheme 1.
Q S Z [R 2 R 1 O CH + NH 2 CSNH 2 76 8 ? d g j N g H R 1 R 2 R 3 Nd H r S I g R 3 8 d g j R 1 R 2 R 3 Nd H r S A N II 2 9NH2CSNHPh R 1 = Fc, R 2 = H, R 3 = Ar; R 1 = Ar, R 2 = H, R 3 = Fc; R 1 , R 2 = FcCH=C(CH 2 ) 3 ; R 3 = Fc, Fc = C 5 H 5 FeC 5 H 4 .With urea and its derivatives, the related condensations were not performed. The prospects for applying the expected products, e.g., as physiologically active substances make it interesting to prepare ferrocenylsubstituted tetrahydropyrimidinones and to study in detail their structure and chemical behavior.In this work we studied the reactions of urea with a,b-unsaturated linear and cyclic ketones containing the ferrocenyl substituent.We found that urea reacts with chalcones IIIa3IIId on refluxing in absolute isopropyl alcohol in the presence of t-BuOK to give 1,2,3,6-tetrahydropyrimidin-2-ones IVa3IVd, respectively, in~70 380% yields (Scheme 2). Scheme 2 9 Q Z Ar O C3R 7776 g Fc [ IIIa!IIId IVa!IVd NH 2 CONH 2 8 ? d N g H Ar Nd H r O i eFc R R = H, A = 4-CH 3 OC 6 H 4 (a); R = H, Ar = 4-BrC 6 H 4 (b); R = H, Ar = Fc (c); R = CH 3 , Ar = Fc (d).The isolated pyrimidin-2-ones IVa3IVd are the only reaction products. These are finely crystalline pale yellow substances stable in storage in the solid state. In common organic solvents (CHCl 3 , CH 2 Cl 2 , CH 3 COCH 3 , CH 3 COOEt, C 6 H 6 , etc.), they rapidly decompose, but in basic solvents (pyridine, morpholine, dimethylformamide, etc.) they are stable.