Abstract
Reaction of 3-(p-toluoyl)propanoic acid, 1a (R = H) with refluxing acetic anhydride resulted quantitatively in 2, a β,γ-unsaturated γ-lactone, which was then converted into 3a, an α,βunsaturated lactone by isomerization with triethylamine. The methyl- substituted compound 1b (R = Me), an analogue of 1a, afforded the 2(5H)-furanone 3b directly by heating with Ac2O. Similar reaction of the cycloalkane- containing oxocarboxylic acids (4,5) led in excellent yields to the fused furanones 6 and 7, while treatment of 2-formyl-, 2-acetyl- and 2-(p-toluoyl)benzoic acids (8a-c) with Ac2O gave the 3-acetoxy-1-(3H)-isobenzofuranones, 9a-c.
Highlights
We recently described several cyclocondensation reactions of 4- and 5-oxocarboxylic acids with amines[1] and bifunctional amino derivatives, such as diamines, amino-alcohols and amino-thiols.[2]
Further studies of the reactivity of cis- and trans- cyclohexane- fused 4-oxocarboxylic acids with various dehydrating agents (H2SO4, PPA, H3PO4, AcCl, Ac2O, and DCC) led to formation of unsaturated lactones exclusively, instead of the expected saturated anthraquinone derivatives. These results prompted us to compare the reactivity of aromatic, aliphatic, and cycloalkanecondensed 4-oxocarboxylic acids with acetic anhydride as a mild and efficient reagent
The typical reaction of 3-(p-toluoyl)propanoic acid, 1a (R = H) (Scheme 1) with an excess of refluxing acetic anhydride after 20 minutes resulted in the unsaturated lactone 2 in excellent yield (88 %), it was isomerized to the 2(5H)-furanone 3a according to the method of Filler et al 12 in the presence of triethylamine in benzene at reflux for 15–18 hours
Summary
We recently described several cyclocondensation reactions of 4- and 5-oxocarboxylic acids with amines[1] and bifunctional amino derivatives, such as diamines, amino-alcohols and amino-thiols.[2]. These results prompted us to compare the reactivity of aromatic-, aliphatic-, and cycloalkanecondensed 4-oxocarboxylic acids with acetic anhydride as a mild and efficient reagent. The typical reaction of 3-(p-toluoyl)propanoic acid, 1a (R = H) (Scheme 1) with an excess of refluxing acetic anhydride after 20 minutes resulted in the unsaturated lactone 2 in excellent yield (88 %), it was isomerized to the 2(5H)-furanone 3a according to the method of Filler et al 12 in the presence of triethylamine in benzene at reflux for 15–18 hours.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
