Asymmetric and Geometry‐Selective α‐Alkenylation of α‐Amino Acids

Abstract

Both E‐ and Z‐N′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K+ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure products under acid conditions reveals quaternary α‐alkenyl amino acids with stereodivergent control of both absolute configuration and double bond geometry.

Konzertierte nukleophile aromatische Substitutionen

“…Dieser jüngsten Arbeit vorangehend haben Clayden et al. umfangreiche alternative Anwendungen dieser Aryltransferreaktionen untersucht, insbesondere bei Ringexpansionsreaktionen, z. B. mit den Substraten 240 und 241 .…”

Amino Acid-Derived trans-N-Chloroformylimidazolidinones: Scalable, Stereoselective Synthesis, Structure, and Utility

“…We have recently described several reactions in which the N-chloroformyl derivative of an imidazolidinone plays a pivotal role, [15][16][17][18] and this work showed that the two diastereoisomers of these carbamoyl chlorides displayed very different reactivity. In one particular family of Bischler-Napieralski-like cyclisations, 16 only the trans isomer was of use.…”

“…Precursors: All esters, amides, and imines (precursors to the N-chloroformylimidazolidinones) were synthesised on 10-30 gram scale according to our previously reported literature protocols. [15][16][17]…”

“…The synthesis of N-chloroformylimidazolidinones on 10-30 gram scale according to our optimised method was previously reported. [16][17] Phosgene solution (15% wt. in toluene, 1.…”

“…The synthesis of N-chloroformylimidazolidinones on a 10−30 g scale according to our optimized method was previously reported. 16,17 Phosgene solution (15% wt in toluene, 1.5 equiv) (handle carefully!) was added dropwise to a solution of the imine (1 equiv) in dry THF (0.5 M) at room temperature under N 2 over After stirring for 5 min, the alkyl halide (1.1 mmol, 1.1 equiv) was added dropwise.…”