Categories: Synthesis of N-Heterocycles >
Synthesis of 2-pyrrolines
A chemoselective intramolecular hydroamination and hydroalkoxylation of readily available α-allenic amines and alcohols provides valuable 2,3-dihydropyrroles and 2,3-dihydrofurans in the presence of low amounts of an air and moisture stable iron catalyst. The mild reaction conditions allow fthe hydrofunctionalization of a wide range of allenes bearing different functional groups in good yields in the absence of base or any sensitive additives.
O. El-Sepelgy, A. Brzozowska, J. Sklyaruk, Y. K. Jang, V. Zubar, M. Rueping, Org. Lett., 2018, 20, 696-699.
Ring-closing metathesis reactions of olefin-containing enamides using ruthenium-based catalysts provides protected five- and six-membered cyclic enamides.
S. S. Kinderman, J. H. van Maarseveen, H. E. Schoemaker, H. Hiemstra, F. P. J. T. Rutjes, Org. Lett., 2001, 3, 2077-2079.
An efficient, scalable and mild cyclocarboamination reaction of nonactivated alkynes with aziridines, catalyzed by low loadings of Lewis or Bronsted acids, provides a wide range of polysubstituted 2,3-dihydropyrroles in a highly regioselective manner through a formal [3+2] cycloaddition.
P. A. Wender, D. Strand, J. Am. Chem. Soc., 2009, 131, 7528-7529.
By using [Rh(NBD)2]BF4 as the catalyst for intermolecular cycloaddition of vinylaziridines with alkynes, a [3 + 2] cycloaddition reaction was achieved with broad substrate scope and high stereoselectivity under mild reaction conditions. When the catalyst was changed to [Rh(η6-C10H8) (COD)]SbF6, the alternative [5 + 2] cycloadducts were selectively formed under otherwise identical conditions.
J.-J. Feng, T.-Y. Lin, C.-Z. Zhu, H. Wang, H.-H. Wu, J. Zhang, J. Am. Chem. Soc., 2016, 138, 2178-2181.
A sequential reaction sequence for the synthesis of 5-aryl-2,3-dihydropyrroles, starting from N-tosyl-protected 2-methylprop-2-en-1-amine, alkynyl bromides, and arylboronic acids, involves nucleophilic addition of the sulfonamide to the alkynyl bromide, followed by a palladium-catalyzed tandem intramolecular Heck and intermolecular Suzuki cross-coupling reaction of the bromoalkene adduct.
J. Peng, Y. Zhao, J. Zhou, Y. Ding, C. Chen, Synthesis, 2014, 46, 1881-1885.
A palladium-catalyzed intramolecular amination of alkenes with tosyl-protected amines was achieved under mild reaction conditions in the presence of chloranil to provide versatile dihydropyrrole derivatives with retention of olefin functionalization in good yields.
B. Jiang, F.-F. Meng, Q.-J. Liang, Y.-H. Xu, T.-P. Loh, Org. Lett., 2017, 19, 914-917.
A Brønsted acid catalyzed cyclization of aminodiazoesters with aldehydes provides a wide range of 5 to 7-membered 3-carboxylate-N-heterocycles. This reaction offers broad substrate scope and functional group compatibility.
Y. Jiao, A. Chen, B. Yu, H. Huang, Org. Lett., 2020, 22, 6031-6034.
Ni(ClO4)2·6H2O can be used as a Lewis acid catalyst for nucleophilic amine ring-opening cyclizations of donor-acceptor (D-A) cyclopropanes to yield vinylogous 4-carboxy- and 4-keto-2,3-dihydropyrroles in good yields under milder reaction conditions than previously reported. The reaction is amenable to a variety of D-A cyclopropanes and primary amines.
M. C. Martin. D. V. Patil, S. France, J. Org. Chem., 2014, 79, 3030-3039.
Cascade reactions of saturated cyclic amines with 2-oxo-2-arylacetic acids enable a highly regioselective and versatile synthesis of acylated N-heterocycles. In this cascade process, the copper catalyst is believed to play a crucial role not only in dehydrogenation but also in the decarboxylation and cross coupling reaction.
X. Shi, X. Chen, M. Wang, X. Zhang, X. Fan, J. Org. Chem., 2018, 83, 6524-6533.
An intramolecular iminium ion cyclization reaction of readily accessible Baylis-Hillman derivatives and aldehydes enables a synthesis of trans-4,5-disubstituted 3-carboxy-4,5-dihydropyrroles in good yield. These dihydropyrroles can easily be converted to pyrroles or pyrrolidines.
J. Yiang, H. Xie, Z. Li, Q. Dang, X. Bai, Org. Lett., 2015, 17, 3810-3813.
N-Sulfonyl-1,2,3-triazoles generate α-imino rhodium carbene complexes, which further react with α,β-unsaturated aldehydes to produce trans-2,3-disubstituted dihydropyrroles. The method can be successfully applied to a one-pot process starting from terminal alkynes.
T. Miura, T. Tanaka, K. Hiraga, S. G. Stewart, M. Murakami, J. Am. Chem. Soc., 2013, 135, 13652-13655.
The combination of I2/PhI(OAc)2 promotes an efficient and practical one-pot reaction of amines with alkyne esters and chalcones under solvent-free ball-milling conditions to afford a variety of polysubstituted trans-2,3-dihydropyrroles in good yields. This protocol furnishes the corresponding pyrroles with the addition of DDQ as oxidant in a subsequent step.
H. Xu, H.-W. Liu, K. Chen, G.-W. Wang, J. Org. Chem., 2018, 83, 6035-6049.