Synthesis Of Cyclic Polybutylene Terephthalate And 3-Oxetanol

Polybutylene terephthalate(PBT)is one of the five engineering plastics.It has the advantages of good hardness and corrosion resistance.So PBT is widely used in medical equipment and precision instruments.In the process of producing PBT,cyclic polybutylene terephthalate is produced.Although the content of these cyclic oligomers are low,they are important indicators for monitoring the quality of PBT.In order to obtain a good quality and moderate priced cyclic oligomer,a simple and practical method for synthesizing these compounds has been developed.In the synthesis of cyclic trimer,the inexpensive p-formylbenzoic acid was used as a starting material,condensed with allyl chloride,and oxidized to give 4-(allyloxycarbonyl)benzoic acid.Then,4-(allyloxycarbonyl)benzoic acid condensed with bis(4-hydroxy butyl)terephthalate,ring closure with Grubbs catalyst and hydrogenation with Pd/C to give cyclic trimer.In particular,the reaction conditions of ring closure with Grubbs catalyst were screened.The recycling yield reached 58%.In this route,cyclic trimers were synthesized in 31% overall yield by 5 steps.The operation is simple and the route is short,which is significantly improved compared with the patent in 15% overall yield by 6 steps.In the synthesis of cyclic tetramer,the target compound was also synthesized by olefin metathesis in a total yield of 22% by 8 steps,which is significantly improved compared with the patent in 8% and 14% overall yield in the literature.In the synthesis of cyclic pentamer,4,4'-(terephthaloyl bis-(oxytetrame thylene oxycarbonyl))benzoic acid(2c)was reacted with sulfoxide chloride,and then condensated with bis-(4-(4-hydroxy-butoxycarbonyl)benzoyl)-1,4-butanediol ether(9a).The yield of this two steps can reach 18%.3-Oxetanol is a very important drug synthesis fragment in pharmaceutical chemistry.In this paper,a route for the synthesis of 3-Oxetanol was optimized.The epichlorohydrin was used as a starting material to undergo ring opening,hydroxyl protection,ester bond hydrolysis,ring closure,and finally the protecting group was removed under weakly acidic conditions to obtain the target compound.In this paper,the regioselective ring opening of epichlorohydrin was investigated.It was found that the high selectivity could be achieved by o-bromobenzoic acid(target product: isomer >98:1),which is significantly improved compared with the literature methods.The structure of the final product was determined by NMR and MS,and its purity was determined by gas phase analysis.