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Synthesis of 1-pyrrolines

Recent Literature

A reductive cleavage of the N-O bond in oxime ether promoted by SmI₂ generates N-centered radicals, that undergo intramolecular cyclization to afford five-membered cyclic imines either via N-centered radical addition or N-centered anion nucleophilic substitution.
F. Huang, S. Zhang, Org. Lett., 2019, 21, 7430-7434.

A synthesis of 1-pyrrolines in good yields from cyclobutanol derivatives and an aminating reagent (MsONH₃OTf) is achieved under mild conditions by C-N bond/C=N bond formation via ring expansion.
D. Zhuang, T. Gatera, Z. An, R. Yan, Org. Lett., 2022, 24, 771-775.

[RuCl₂(CO)₃]₂/dppp is a highly effective catalyst system for the intramolecular oxidative amination of various aminoalkenes in presence of K₂CO₃ and allyl acetate in N-methylpiperidine to give the corresponding cyclic imines and indoles in excellent yields.
T. Kondo, T. Okada, T.-A. Mitsudo, J. Am. Chem. Soc., 2002, 124, 186-187.

Asymmetric cross-electrophile difunctionalization of tethered alkenes is a powerful tool for the production of chiral cyclic scaffolds. An enantioselective aza-Heck cyclization/cross-coupling sequence proceeds with primary, secondary, and a few tertiary alkyl iodides, to provide highly enantioenriched pyrrolines with improved molecular diversity under mild conditions.
X.-G. Jia, Q.-W. Yao, X.-Z. Shu, J. Am. Chem. Soc., 2022, 144, 13461-13467.

Upon treatment with aqueous sodium hydroxide in DMF, a range of chalcones underwent Michael addition reactions with nitroalkanes. The resulting adducts were reduced in situ with Zn/HCl (aq) to afford substituted Δ¹-pyrrolines in high yields after a cyclization.
Y. Liang, D. Dong, Y. Lu, Y. Wang, W. Pan, Y. Chai, Q. Liu, Synthesis, 2006, 3301-3304.

Pd-catalyzed intramolecular cyclizations of oxime esters with 1,2-dialkylated alkenes provide an entry to dihydropyrroles. Substrate and catalyst controlled strategies for selective product formation are outlined.
N. J. Race, J. F. Bower, Org. Lett., 2013, 15, 4616-4619.

Simple trialkyl rare-earth metal complexes catalyze a highly atom-economic and stereoselective tandem insertion of aliphatic nitriles and unactivated alkenes to the N-H bond of secondary aliphatic amines to provide of cyclic amidines under mild reaction conditions.
J. Hou, G. Yang, Z. Chai, J. Org. Chem., 2022, 87, 453-463.