Reactions of alkenoic acids with sulfur trioxide; sulfonation and sulfo-lactonization

✍ Scribed by Ruud M. Schonk; B. H. Bakker; H. Cerfontain

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 882 KB
• Volume: 111
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19921111103

✦ Synopsis

Abstract

The reactions of the alkenoic acid derivatives 1a–19a with sulfur trioxide were studied in the temperature range −60 to 25°C using dichloromethane as solvent and 1.5 equiv. of dioxane as reactivity moderator. The alkenoic acids 13a and 14a, having a ‐(CH~2~)~4~‐ and ‐(CH~2~)~7~‐ linkage between the C = C and CO~2~H moieties, respectively, react as simple alkenes; at low temperatures, they yield the β‐sultones 13d, 14c and 14d, which at 25°C are slowly converted into the corresponding carbyl sulfates 13h, 14g and 14h. Reactions of the alkenoic acids 4a–12a with 1.2 equiv. of SO~3~ at −60°C leads to the quantitative formation of the γ‐lactones 4e–9e and 11e, and in some cases to the γ‐lactones 10f and 12f. The stereochemistry of this sulfo‐lactonization is dependent on the SO~3~ concentration, which is clearly demonstrated for the reactions of (E)‐ (5a) and (Z)‐3‐hexenoic acid (6a) with 1.0 equiv. and 10.0 equiv. of SO~3~. For reactions of 5a and 6a with ≤ 1.0 equiv. of SO~3~, the β‐sultones 5c and 6c are the presumed sole initial products undergoing subsequent lactonization. Upon using an excess of SO~3~, in addition, the corresponding carbyl sulfates 5g and 6g will undergo sulfocyclization to give the cis‐ (6e) and trans‐γ‐lactones (5e), respectively.

Reaction of 5‐norbornene‐endo‐2,endo‐3‐dicarboxylic anhydride (15a) with 1.2 equiv. of SO~3~ at 25°C yields slowly but quantitatively the β‐sultone 15c. This β‐sultone is surprisingly stable and it is very slowly converted into the γ‐lactone 15e only in the presence of H~2~O. Reactions of the norbornenecarboxylic acids and derivatives 16a–19a with SO~3~ yield the γ‐lactones 16e, 18e and 19e. Mechanisms for the formation of the various products are suggested.