65061-68-9Relevant academic research and scientific papers
ACYLATION D'ALCENES DANS LE SYSTEME ACYLANT ACIDE TRIFLUOROMETHANESULFONIQUE-HALOGENURE D'ACIDE
Roussel, Christian,Rajoharison, Harivelo G.,Metzger, Jacques
, p. 613 - 618 (2007/10/03)
The diacylation of 2-methyl-2-pentene and of related alcoholic precursors with trifluoromethanesulphonic acid/acetyl chloride was investigated. The initially formed pyrylium salts were converted directly into the corresponding pyridines. The influence of the reaction conditions (temperature; molar ratios AcCl/F3CSO3H/alkene; experimental procedure) was thoroughly examined permitting the observation of new aspects for the examined synthesis of pyrylium salts e.g.: a) formation of less substituted pyrylium salts 2 up to 94 percent selectivity; b) direct access to isomeric pyrylium salts 1 and 2 depending on the reaction conditions; c) formation of triacylation products 3, 4 which could be suppressed in favour of 2. The described procedure presents also experimental advantages (no crackings; easily tractable reaction mixtures).
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.
