Synthesis of Tricyclic Diesters
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Synthesis of Tricyclic Diesters E. K. Makhmudovaa,*, R. A. Rasulovaa, V. S. Kadyrlya, and M. J. Ibragimovaa a
Mammadaliyev Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, 1025 Azerbaijan *e-mail: [email protected] Received December 25, 2019; revised December 29, 2019; accepted December 31, 2019
Abstract—The addition of saturated monobasic C3–C5 carboxylic acids to unsaturated tricyclic ester, tricyclo[5.2.1.02,6]dec-3-en-8-yl propanoate, in the presence of boron trifluoride–diethyl ether complex gave the corresponding tricyclic diesters in 76.8–88.5 wt % yield. The product structure was confirmed by IR and 1H and 13C NMR spectra. The synthesized diesters possess a pleasant odor and can be recommended for use as synthetic fragrance substances in perfumery. Keywords: saturated carboxylic acids, tricyclic ester, 8-propanoyloxytricyclodec-3-ene, catalyst, boron trifluoride–diethyl ether complex, tricyclic diesters
DOI: 10.1134/S1070428020100292 Persistent interest in the chemistry of cyclic monoand diesters is determined by the wide range of applications of these compounds. They are used as aromatizers in perfumery [1–3], oil additives [4, 5], plasticizers for polymeric compositions [6, 7], etc. With the goal of improving the technology for the preparation of tricyclic esters we previously studied the addition of formic and acetic acids to the double bonds of dicyclopentadiene and obtained the corresponding tricyclic diesters, among which the diacetate was found to have a pleasant citrus odor [8]. In the present work we studied the addition of saturated monobasic C3–C5 carboxylic acids to tricyclo[5.2.1.02,6]dec-3-en-8-yl propanoate (1) in the presence of boron trifluoride–diethyl ether complex and synthesized new tricyclic diesters (Scheme 1). Initial ester 1 was prepared by reaction of tricyclo[5.2.1.02,6]deca-3,8-diene with propionic acid using BF3·Et2O as catalyst [9]. The reaction conditions were optimized by varying the temperature (60–90°C), molar reactant ratio (1:1 to 1:1.75), amount of the catalyst (0.2–0.8%), and reaction time (2–5 h) in the reaction of 1 with propionic acid (2). The best yield of 5 (~89%) was obtained at 80°C using 1.5 equiv of acid 2 and 0.6 wt % of BF3· Et2O, the reaction time being 4 h. Under the optimal conditions, the addition of butyric and valeric acids 3
and 4 to compound 1 gave diesters 6 and 7 in 77 and 80% yield, respectively. According to the GLC data, diesters 5–7 contained 98–99% of the main substance. Their structure was confirmed by IR and 1H and 13C NMR spectra. As followed from the NMR data, the addition was stereoselective, and the products were exo,exo isomers. The carbonyl carbon nuclei of 5–7 resonated in their 13C NMR spectra at δ 160.87–165.24 ppm. The IR C spectra of 5–7 showed strong absorption bands at 3000–2860 (C–H), 1727–1740 (C=O), 1458 (CH 2), 1380 (CH3), and 1180–1230 cm–1 (CO–O). Tricyclo[5.2.1.02,6]dec-3-en-8-yl propanoate (1). A mixture of 132 g (1 mol) of tricyclo[5.2.1.02,6]deca3,8-diene, 74 g (1
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