Synthesis and properties of cyclic acetals of Wallach ketone

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Abstract
Objectives . The work set out to obtain the corresponding cyclohexenyl derivatives of 1,4-dioxaspiro[4.5]decane, 1,5-dioxaspiro[5.5]undecane, and 1,4-dithiaspiro[4.5]decane by condensation of 2-(cyclohexen-1-yl)cyclohexanone (Wallach ketone) with 1,2-, 1,3-diols, and 1,2-ethanedithiol; to determine reaction duration and process temperature at which the maximum possible yield of the target cyclic derivatives of 2-(cyclohexen-1-yl)cyclohexanone is achieved; to evaluate the anticorrosive properties of the obtained acetals in an acidic medium; to carry out dichlorocarbenation using 1,4-dioxaspiro[4.5]decane as an example, and to establish the structure of the obtained isomers. Methods . Target compounds including cyclic acetals were obtained by a classical organic synthesis method involving condensation of 2-(cyclohexen-1-yl)cyclohexanone (Wallach ketone) with 1,2-, 1,3-diols, and 1,2-ethanedithiol. The following analysis methods were used to determine the qualitative and quantitative composition of the reaction masses: gas–liquid chromatography (Crystallux-4000M chromatograph with a flame ionization detector, a 25 m × 0.33 mm capillary column containing 100% polydimethylsiloxane as a stationary phase 0.5 μm), nuclear magnetic resonance spectroscopy (BrukerAM-500 device with operating frequencies of 500 and 125 MHz), and elemental microanalysis (rapid gravimetry method). Chlorine and sulfur were determined by the Schöniger method. Results. Under conditions of thermal heating of Wallach ketone with 1,2-, 1,3-diols, and 1,2-ethanedithiol, 1,4-dioxaspiro[4.5]decane, 1,5-dioxaspiro[5.5]undecane, and 1,4-dithiaspiro[4.5]decane were obtained with a yield of 95%. 5,5-Dimethyldioxane derivative was found to have a moderate inhibitory effect on acid corrosion of carbon steel St20 at a temperature of 60°С. Dichlorocarbenation of 1,4-dioxaspiro[4.5]decane was shown to occur with the formation of a mixture of two diastereomers (ratio is 1 : 2) as evidenced by doubled signals of carbon atoms in the carbon spectrum. Conclusions . 2-(Cyclohexen-1-yl)cyclohexanone 1 condenses with 1,2-, 1,3-diols, and ethanedithiol to form the corresponding spirocyclic derivatives in high yields. It is shown that 1,4-dioxaspiro[4.5]decane undergoes dichlorocarbenation under Mąkosza reaction conditions to form polycyclic gem-dichlorocyclopropane as a mixture of two diastereomers. 7-(Сyclohex-1-en-1-yl)-3,3-dimethyl-1,5- dioxaspiro[5.5]undecane is confirmed to inhibit steel corrosion in acidic media.

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