title: Highly efficient, one-step macrocyclizations assisted by the folding and preorganization of precursor oligomers.
abstract: Highly efficient, one-step macrocyclizations leading to the formation of macrocyclic hexa(aramides) in high yields (69-82%) are described. The one-step macrocyclizations were facilitated by the preorganization or folding of the backbones of uncyclized precursors in the course of macrocyclization. The preorganization of backbones was achieved by the presence of localized three-centered hydrogen bonds that were adopted in the design of a class of closely related, backbone-rigidified foldamers. The macrocyclization involved reactions between diacid chloride 1 and diamine 2. The crude reaction mixtures and products were conveniently examined by mass spectrometric method (MALDI-TOF). Compared to most traditional one-step macrocyclizations that usually require high dilution conditions and often lead to very low overall yields of the desired products, cyclic hexamers 3 were obtained as the overwhelmingly major product under a variety of reaction conditions, suggesting the generality of this approach.
authors.affiliation: Department of Chemistry, Natural Sciences Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, USA.
authors.forename: Lihua
authors.initials: L
authors.lastname: Yuan
authors.forename: Wen
authors.initials: W
authors.lastname: Feng
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamato
authors.forename: Adam R
authors.initials: AR
authors.lastname: Sanford
authors.forename: Dingguo
authors.initials: D
authors.lastname: Xu
authors.forename: Hua
authors.initials: H
authors.lastname: Guo
authors.forename: Bing
authors.initials: B
authors.lastname: Gong
mesh_terms: D003500:Cyclization; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D009757:Nylons / Q000737:chemistry*; D010655:Phenylenediamines / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D009757:Nylons; D010655:Phenylenediamines