21399-24-6Relevant articles and documents
Syntheses of Pyrroles, Pyridines, and Ketonitriles via Catalytic Carbopalladation of Dinitriles
Qi, Linjun,Li, Renhao,Yao, Xinrong,Zhen, Qianqian,Ye, Pengqing,Shao, Yinlin,Chen, Jiuxi
supporting information, p. 1097 - 1108 (2020/01/22)
The first example of the Pd-catalyzed addition of organoboron reagents to dinitriles, as an efficient means of preparing 2,5-diarylpyrroles and 2,6-diarylpyridines, has been discussed here. Furthermore, the highly selective carbopalladation of dinitriles with organoboron reagents to give long-chain ketonitriles has been developed as well. Based on the broad scope of substrates, excellent functional group tolerance, and use of commercially available substrates, the Pd-catalyzed addition reaction of arylboronic acid and dinitriles is expected to be significant in future synthetic procedures.
Microwave mediated facile one-pot synthesis of polyarylpyrroles from but-2-ene- and but-2-yne-1,4-diones
Rao, H. Surya Prakash,Jothilingam,Scheeren, Hans W.
, p. 1625 - 1630 (2007/10/03)
Several pyrrole derivates with multiple aryl substituents were prepared conveniently in a one pot-reaction from but-2-ene-1,4-diones and but-2-yne-1,4-diones via hydrogenation of the carbon-carbon double bond/triple bond followed by amination-cyclization. The reaction could be performed with ammonium formate or alkyl/arylammonium formates under Pd/C in polyethylene glycol-200 (PEG-200) under microwave irradiation. Using this procedure, different aryl-substituted pyrroles were prepared. Furthermore, studies on microwave vs thermal conditions indicate faster heating under microwave conditions was responsible for rate enhancement.
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.
