Categories: Synthesis of N-Heterocycles >
Synthesis of 1-pyrrolines
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.
[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.
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.