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Dynamic thermodynamic resolution of lithiated N-Boc-N′-alkylpiperazines

✍ Scribed by Steven P. Robinson; Nadeem S. Sheikh; Carl A. Baxter; Iain Coldham

Book ID
104097819
Publisher
Elsevier Science
Year
2010
Tongue
French
Weight
521 KB
Volume
51
Category
Article
ISSN
0040-4039

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✦ Synopsis

Deprotonation of N-Boc-N 0 -alkylpiperazines with sec-BuLi in Et 2 O-TMEDA gave the 2-lithio derivatives which were resolved in the presence of a chiral ligand. The best ligands for the asymmetric substitution were diamino-alkoxides that promoted a dynamic thermodynamic resolution (DTR) of the organolithium at À30 °C. Electrophilic quench gave enantiomerically enriched 2-substituted piperazines. Of a selection of piperazines, the N 0 -t-butyl derivative gave the best results, with the product N-Boc-N 0 -t-butyl-2-substituted piperazines being formed with enantiomer ratios up to 81:19.

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