A New Synthetic Method for α‐Alkoxycarbonyl Iminium Salt and Its Reaction with Nucleophiles.

Abstract

Aminocarboxylic acids (hydrazinocarboxylic acids) and esters P 0270 A New Synthetic Method for α-Alkoxycarbonyl Iminium Salt and Its Reaction with Nucleophiles. -(SHIMIZU*, M.; ITOU, H.; MIURA, M.; J. Am. Chem. Soc. 127 (2005) 10, 3296-3297; Dep. Chem. Mater., Fac. Eng., Mie Univ., Tsu, Mie 514, Japan; Eng.) -Nuesgen 31-072

α-Imino Esters in Organic Synthesis: Recent Advances

“…Grignard Addition to Iminium Salts, in Situ Generated by Oxidation of Amino Ketene Silyl Acetales a substituted imino lactone 16a with MeMgBr, led to (4R,10aS)tetrahydro-1H- [1,4]oxazino [4,3-a]azepine-1,6(9H)-dione 19a, while the diastereoisomeric compound (4R,10aR)-19b (n = 2) was formed by starting from addition of but-3-enylMgBr to methyl substituted imino lactone 16b (Scheme 5). The Grignard addition to α-alkoxycarbonyl iminium salts 29 in situ generated by oxidation of amino ketene silyl acetales 20 was reported by Shimizu et al 37 Treatment of 1-ethoxy-2dibenzylamino-1-trimethylsiloxyethylene 20a with 2 equiv of Grignard reagent in the presence of DDQ (1 equiv) in DME-DCM under an atmosphere of argon at −55 °C, then at room temperature for 15 h, afforded α-amino esters 21 in 24−75% yields. Reaction with t-BuMgBr did not occur.…”