Regiospecific synthesis of terephthalates
View Patent ↗A method for preparing 1,4-biscarboxylic acid esters of benzene is provided.
1. A method for the synthesis of a compound of formula (I):
wherein R and R 1 are individually selected from H, alkyl, arylalkyl, cycloalkyl or cycloalkylalkyl comprising: reacting a coumalate compound of formula (II):
optionally in the presence of a solvent, with a captodative alkene of formula (III), (IV) or (V):
wherein R 2 is —OR, —SR, halo (F, Cl, Br, I), (R) 2 N, RC(O)— or —O[Si(R a )(R b )(R c )] wherein each of R a , R b or R c are individually selected from (C 1 -C 6 )alkyl, and wherein X and Y are individually R or R 1 , or together are —(CH 2 ) n —, wherein n is 2-3 and —(CH 2 ) n — is optionally substituted with R, so as to yield a compound of formula (I).
2. The method of claim 1 wherein each of R, R 1 , X or Y is (C 1 -C 4 )alkyl.
3. The method of claim 2 wherein each of R, R 1 , X or Y is methyl.
4. The method of claim 3 wherein R a , R b and R c are methyl.
5. The method of claim 4 where R 2 is methoxy.
6. The method of claim 1 that is carried out in the absence of solvent.
7. The method of claim 1 that is carried out at a molar ratio of III, IV or V to (II) of about 3:1.
8. The method of claim 7 wherein the reaction is carried out about 150-200° C.
9. The method of claim 8 wherein the reaction is carried out for 3-16 hours.
10. The method of claim 1 wherein the compound of formula I is dimethyl terephthalate.
11. The method of claim 1 which is carried out without a metal catalyst.