Synthesis of 5-butoxybicyclo[2.2.1]heptan-2-yl acrylate and methacrylate

Abstract

SHORT COMMUNICATIONSEsters derived from unsaturated acids and alicyclic alcohols or diols are reactive monomers for the preparation of practically important polymers for various fields of science and technology [1]. We previously synthesized various functionalized norbornyl acrylates and methacrylates and showed that these compounds can be used as reactive monomers for the preparation of practically important polymers [2]. With a view to extend the series of available monomers in the present work we examined [4 + 2]-cycloaddition of cyclopentadiene with butyl vinyl ether in the presence of nanosized TiO 2 (20 nm). 5-Butoxybicyclo[2.2.1]hept-2-ene thus obtained was then brought into reactions with acrylic and methacrylic acids in the presence of boron trifluoride-diethyl ether complex as catalyst.Tricyclo[5.2.1,0 2,6 ]deca-3,8-diene (I) decomposed at 160°C to produce cyclopentadiene which reacted with butyl vinyl ether to give 5-butoxybicyclo[2.2.1]-hept-2-ene (II) [3] (Scheme 1).According to the GLC data, ether II was formed as a mixture of two stereoisomers, the exo/endo ratio being 60 : 40. According to [5], the endo isomer undergoes thermal isomerization into thermodynamically more stable exo isomer (Scheme 2); therefore, the obtained mixture of isomers was heated so that the fraction of exo-II reached 99% (GLC). Scheme 1.I 2 BuOCH=CH 2 BuO II 2 Unlike known procedure, we used nanosized (20-nm) titanium(IV) oxide as catalyst which ensured higher yield of II. By studying the effects of different factors on the formation of bicyclic ether II we found the following optimal conditions: molar ratio IBuOCH=CH 2 1 : 4, amount of the catalyst 0.5 wt % (relative to I), temperature 170°C, reaction time 5 h. Under these conditions the yield of II was 73% against 31% obtained in [4]. Scheme 2.BuO endo-IIWith the goal of obtaining new monomers we then examined the addition of acrylic and methacrylic acids to ether exo-II in the presence of BF 3 · O(Et) 2 as homogeneous catalyst. These reactions afforded the corresponding esters III and IV (Scheme 3). The optimal conditions for the synthesis of ester III (yield 85%) were as follows: molar ratio II-CH 2 =CHCOOH 1 : 2, 0.15 wt % of BF 3 · O(Et) 2 (relative to II), temperature 80°C, reaction time 4 h. Under these conditions, methacrylic acid reacted with exo-II in stereo-and regioselective fashion, yielding 80% of exo,exo-ester IV. In the syntheses of esters III and IV, 0.1 wt % of hydroquinone (relative to unsaturated acid) was added as inhibitor to prevent polymerization of the reactants and products.The purity of esters III and IV was checked by GLC, and their structure was proved by IR and 1 H and 13 C NMR spectroscopy. According to the GLC data, the purity of the initial compounds and esters III and IV was 98.6-99.0%.

Synthesis of 8-acetoxytetracyclo[4.4.12.5.17.10.01.6]dodec-3-ene and diesters of C1-C5 acids on its basis

“…The product obtained was heated at 200°C for 1 h to carry out isomerization of the mixture to most stable exo-exo-isomer [7]. This process resulted in the formation of monoester containing 99.9% of exo-exoand 0.1% of endo-endo-isomer.…”