A Simple Method of Synthesis of (±)-2,3-Diarylpiperazines and a Novel Method of Resolution of (±)-2,3-Diphenylpiperazine
摘要:
Intramolecular reductive coupling of diimines in the presence of Zn/Ti((OPr)-Pr-i)(2)Cl-2 gives the corresponding (+/-)-2,3-diarylpiperazines in 73-83% yields with dl/meso ratio > 99%: < 1%. The (+/-)-2,3-diphenylpiperazine obtained in this way was readily resolved partially using L-(+)-tartaric acid, and the enantiomeric purity was enhanced to > 99% ee via preparation of hydrogen-bonded salt aggregates using oxalic acid.
Iridium catalysed synthesis of piperazines from diols
作者:Lars Ulrik Nordstrøm、Robert Madsen
DOI:10.1039/b712685a
日期:——
A green and atom-economical method has been developed for the synthesis of piperazines by cyclocondensation of diols and amines in aqueous media in the presence of a catalytic amount of [Cp*IrCl2]2.
Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent
New chiral titanium complexes for enantioselective reductive cyclizations of diimines to trans-2,3-diarylpiperazines
作者:Pothiappan Vairaprakash、Mariappan Periasamy
DOI:10.1016/j.tetlet.2007.12.038
日期:2008.2
Enantioselective intramolecular reductive coupling of diimines by chiral titanium complexes, prepared using a titanium(IV) reagent and hemisalen ligands derived from chiral β-amino alcohols, gives trans-2,3-diarylpiperazines in up to 97% ee.