Revisit of Thiele’s acid synthesis from CO2 and cyclopentadiene and use for TCD-amine preparation with all-endo specific stereochemistry

This study provides a mild procedure using CO 2 , cyclopentadiene, and sodium tert -butoxide for Thiele’s acid in good yields and high purity. The product distribution of Thiele's acid and other isomeric forms can be tuned by utilizing different metal cations. Among the bases we have tried, sodium tert -butoxide can selectively provide Thiele’s acid as the major product in 72 % isolated yield, along with an endo , endo -pentacyclopentadecadienetricarboxylic acid, denoted as PCPD-triacid as the side product. Thiele’s acid and PCPD-triacid can be hydrogenated in aqueous alkaline solution to give the corresponding all- endo tetrahydro-derivatives, denoted as THDCPD-diacid and THPCPD-triacid . Functional group transformation of the carboxylic acids to alcohols and amines, such as THDCPD-diol and THDCPD-diamine , has been successfully demonstrated. Their chemical structures and stereochemistry are confirmed by X-ray crystallographic analysis. THDCPD-diamine is stereochemically complementary to the commercially available TCD-diamine with high purity and can serve as versatile polymer monomers or cross-linking agents, significantly expanding their potential for use in various applications. • A mild route from CO₂ and cyclopentadiene gives Thiele’s acid in high yield and purity. • THDCPD-diacid was converted to THDCPD-diol and diamine with defined stereochemistry. • Hydrogenation in aqueous alkaline conditions yields all-endo THDCPD-diacid and THPCPD-triacid. • THDCPD-diamine complements TCD-diamine and is useful for polymers or cross-linking agents.