title: Umpolung Reactions of α-Imino Esters: Useful Methods for the Preparation of α-Amino Acid Frameworks.
abstract: This paper summarizes our recent efforts toward the development of tandem reactions utilizing umpolung reactions of α-imino esters. A highly diastereoselective tandem N-alkylation-Mannich reaction of α-imino esters was developed. A tandem N-alkylation-addition reaction of α-imino esters derived from ethyl glyoxylate with various aldehydes proceeded to give 1,2-amino alcohols. The same reaction also proceeded efficiently using a novel flow system comprising two connected microreactors. Novel syntheses of α-quaternary alkynyl amino esters and allenoates were developed through the use of umpolung N-addition to β,γ-alkynyl α-imino esters, followed by regioselective acylation. In addition, a highly regioselective tandem N-alkylation-vinylogous aldol reaction of β,γ-alkenyl α-imino esters was discovered. N-Alkylation of α-iminophosphonates followed by a Horner-Wadsworth-Emmons reaction with aldehydes occurred to afford enamines, which can be used in a four-component coupling reaction with methyl vinyl ketone. α-N-Acyloxyimino esters served as highly efficient substrates for the N,N,C-trialkylation reaction to introduce various nucleophiles at the imino nitrogen and carbon atoms.
authors.affiliation: Department of Chemistry for Materials, Graduate School of Engineering Mie University, Tsu Mie, 514-8507, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Mizota
authors.affiliation: Department of Chemistry for Materials, Graduate School of Engineering Mie University, Tsu Mie, 514-8507, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D000478:Alkylation; D000596:Amino Acids / Q000138:chemical synthesis*; D060326:Chemistry Techniques, Synthetic; D004952:Esters / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D007783:Lactones / Q000138:chemical synthesis; D008956:Models, Chemical; D063065:Organophosphonates / Q000138:chemical synthesis / Q000737:chemistry; D017646:Organosilicon Compounds / Q000737:chemistry; D011753:Pyrones / Q000138:chemical synthesis; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D004952:Esters; D007097:Imines; D007783:Lactones; D063065:Organophosphonates; D017646:Organosilicon Compounds; D011753:Pyrones
keywords: alkylation; amino acids; synthetic methods; tandem reactions; umpolung