108154-12-7Relevant academic research and scientific papers
Diacylation of alkenes catalyzed by sulfonic acids 3: application of weak sulfonic acids to the regioselective synthesis of pyrylium salts from isoolefins and linear olefins
Rajoharison, Harivelo G.,Roussel, Christian
, p. 307 - 313 (2007/10/02)
The use of weak sulfonic acids (methanesulfonic and α-carboxyalkanesulfonic acids) as catalysts in diacylation of disymmetrical isoalkenes by carboxylic acid anhydrides afford almost exclusively the more substituted pyrylium salt.Particularly, simple isoalkenes (generated in situ from dimethyl alkyl carbinols) and citronellol lead 2,3,4,6-tetrasubstituted pyrylium salts in high yields.Diacylation of 1-alkenes lead to 2,3,6-trialkyl-substituted pyrylium without isomerization but in low yield.The observed lower regioselectivities in comparative reactions catalyzed by strong protonic acids (perchloric acid or trifluoromethanesulfonic acid which are the classical catalysts in this kind of synthesis) confirm that the strenght of the catalyst governs the regioselectivity of the diacylation of olefins when carboxylic acid anhydrides are used as sources of acylating agents.In all cases, the obtained pyrylium salts were transformed into the corresponding pyridines by treatment with concentrated ammonia.
