STEREOSELECTIVE SYNTHESIS OF TRANS-β-METHOXYCARBONYL-γ-ARYL-γ-BUTYROLACTONES

ABSTRACT

Stereoselective synthesis of trans-β-methoxycarbonyl-γ-aryl-γ-butyrolactones (5) by the reaction of methoxycarbonylmethyl triphenyl arsonium bromide (1) and 2,2-dimethyl-5-substituted-benzal-1,3-dioxa-4,6-dioxa-4,6-dione (2) is carried out in the presence of potassium carbonate and trace water in dimethoxyethane. 1,2-Cis-cyclopropane 3 is formed as an intermediate. The stability of compound 3 in water is related to the property of the aryl substituent. With strong electron-donating groups [2a–c, Ar=4-CH₃O‒C₆H₄; 3,4-OCH₂O‒C₆H₃ or 4-(CH₃)₂N‒C₆H₄] at room temperature 3 is formed in situ and transformed to γ-butyrolactones 5a–c immediately, whereas when the aryl substituent is H or a weak electron-donating or electron-withdrawing group (2d–g, Ar=4‒CH₃-C₆H₄; C₆H₅; 4-Cl‒C₆H₄ or 4-NO₂‒C₆H₄), 3 is stable to water at room temperature. On further heating in acetone, 3 is transformed to γ-butyrolactones 5d–g (stepwise synthesis). One-pot synthesis of 5d–g from the reaction of 1 with 2d–g is also studied.

Keywords:

• Arsenic ylide
• Stepwise synthesis
• One-pot synthesis
• γ-Butyrolactone
• Stereoselective synthesis

ACKNOWLEDGMENT

Thanks are due to the National Natural Science Foundation of China and Laboratory of Organometallic Chemistry of Academia Sinica for financial support.