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Abstract
The aim of the present work is to find potential oxidation inhibitors to act as antioxidants for industrial lubricating oils such as turbine oils.The research done in this article could be regarded as an extension to our previous work for constructing phenols containing fused chromenopyrimidines heterocycles through reactions of the key compound 1 with a variety of reagents. The interaction between 1 and malononitrile in refluxing ethanol delivered the (3).In the same manner 5, was synesized via reaction of compound 4 with malononitrile.Reaction of chromene 1 and formamide furnished the aminopyrimidine 6 in 70% yield. In contrast, cyclocondensation of compound 1with hot formic acid resulted in the formation of the pyrimidinone 7 in 20% yields. The interaction between the chromene 1 and phenyl isothiocyanate in refluxing absolute ethanol led to the formation of 8 .Moreover, reaction of 1 with carbon disulphide in presence of KOH afforded the corresponding 9. Quite similar chemistry was involved in the formation of the aminopyrimidines 10a, b by reaction of 1 with urea and/or thiourea. Treatment of 1 with triethyl orthoformate at reflux gave the corresponding ethyl 11.Compound 11 was used as precursor for the synthesis of substituted pyrimidine ring by refluxing 11 with p-ansidine in absolute ethanol to give the corresponding 12. An additional pathway for synthesis of substituted chromenopyrimideine derivatives 13 was achieved through reaction of the title compound 1 with acetic anhydride. Thus, refluxing compound 1 in a mixture of acetic anhydride and glacial acetic acid for several hours resulted in formation of the pyrimidine 13.Recently, we described a new, simple and efficient synthesis of 15a and 15b by reaction of 14a or 14b by reaction with malononitrile in refluxing ethanol containing catalytic amount of piperdine. Synthesis of 18 derivatives was achieved by reaction of 16 with 2-aminobenzothiazole 17 in refluxing ethanol to give 18. Quite similar chemistry was involved in the formation of 20. PART (II) Synthesis Of New Phenolic Compounds Linked Heterocycles When compound 1 was coupled to different aryl diazonium chloride, the diazonium salt coupled in position 6 in the chromene ring giving 22a-k .We aimed to investigate further the behavior of the 1 towards aromatic aldehydes such as benzaldehyde, p-anisaldehydeand 3-methoxy-4-hydroxybenzaldehyde. The reactions were performed in refluxing ethanol containing a catalytic amount of triethylamine. An even more convenient access for constructing phenols linked with heterocycles such as tetrahydroqunoline based on the one pot reaction of 16, cyclohexanone and aryl amines Treatment of compound 1 with acetyl acetone in refluxing ethanol containing catalytic amount of triethylamine gave 27.Treatment of 3-methyl-1H-pyrazol-5(4H)-one 28 in ethanol and two moles of p-hydroxybenzaldehyde in presence of ammonium acetate afforded 31. PART (III)
Evaluation of compounds 22a-k as antioxidant on base oil of viscosity grade 68 The base oil used for evaluation versus addition of different antioxidant 22a-k is turbine oil of viscosity grade 68; the base oil, was evaluated using the standard international test methods. The addition of antioxidant 22a, e, f, I, k showed marked increase in oxidation stability test especially 22k compared with the base oil containing international commercial antioxidant.