u00b0 c and acidified with sulfuric acid to ph 1 0 a white precipitate of 2 5 dimethylene 3 enedioic ester is immediately appeared the precipitate is filtered and dried to yield 4 8 g of 2 5 dimethylene 3 enedioic ester 2 5 dimethylene 3 enedioic ester is produced as described in example 15 to a solution of 2 5 dimethylene 3 enedioic ester 10 g in thf 60 ml is added catalytic amount 200 mg of sncl 4 the reaction mixture turned light brown immediately the brown mixture is refluxed under nitrogen for 12 hours the reaction mixture is quenched with 10 na 2 co 3 solution the organic layer is washed with water dried under sodium sulfate and concentrated to produce brown solid 6 8 g as a product the product is directly used for the subsequent steps without further purifications cyclization reaction product as produced above in example 16 is dissolved in 60 ml thf a catalytic amount of 10 rh c 10 mg is added to the reaction the reaction mixture is transferred to the high pressure hydrogenation reactor and heated to 120 u00b0 c under high pressure the reaction mixture is analyzed for product formation every 1 hour the reaction is completed after 6 hours at 120 u00b0 c the reaction mixture is filtered to remove rh c and evaporated to remove thf to produce terephthalic ester as.