97405-82-8Relevant academic research and scientific papers
Woollins reagent: A chemoselective reducing agent for 1,4-enediones and 1,4-ynediones to saturated 1,4-diones
Mandal, Madhumita,Chatterjee, Sourav,Jaisankar, Parasuraman
, p. 2615 - 2618,4 (2012/12/12)
Woollins reagent was found to act as a highly chemoselective reagent for the reduction of a wide range of 1,4-enediones and 1,4-ynediones in methanol to afford the corresponding saturated 1,4-diketones in good yields under mild reaction conditions.
Intermediates in the Paal-Knorr Synthesis of Pyrroles
Amarnath, Venkataraman,Anthony, Douglas C.,Amarnath, Kalyani,Valentine, William M.,Wetterau, Lawrence A.,Graham, Doyle G.
, p. 6924 - 6931 (2007/10/02)
The mechanism of Paal-Knorr reaction between a 1,4-dicarbonyl compound and ammonia or a primary amine to form a pyrrole is explored.In aprotic solvents and in aqueous solutions near neutrality, d,l diastereomers of 3,4-dimethyl- and 3,4-diethyl-2,5-hexanediones (1r and 2r) formed pyrroles 1.3-57.0 times faster than the corresponding meso diastereomers (1m and 2m).This contradicts any intermediate, such as the enamine 15, which does not remain saturated at both the 3- and 4-positions through the rate-determining step.The demonstrated stereoisomeric difference in reactivity coupled with the following results support the hemiaminal (9) as the intermediate undergoing cyclization in the rate-limiting step of the Paal-Knorr reaction: (1) The reaction rate was adversely affected by increase in the size of the alkyl substituents on the dione. (2) Racemic 2,3-dimethyl-1,4-diphenyl-1,4-butanedione (3r) was more reactive toward ammonium acetate (2.2:1) and 2-aminoethanol (11.2:1) than the meso isomer (3m), ruling out the involvement of the less substituted enamine 14. (3) The relative rate of pyrrole formation of 1,4-diphenyl-1,4-butanedione (5) and its dimethoxy (6) and dinitro (7) derivatives (1:0.3:6) does not support cyclization of the imine (11) to the pyrrolinium ion (12). (4) The rates of reaction of 2,2,3,3-tetradeuterio-1,4-diphenyl-1,4-butanedione (5D) and perdeuterio-2,5-hexanedione (4D) were very close to those of unlabeled diketones, indicating the absence of a primary isotope effect in the reaction. (5) Neither the isomerization of the unreacted diastereomers of 1, 2, and 3 nor hydrogen exchange of 4D and 5D was detected during the reaction.
