Modulation of the Cs2CO3-promoted catalytic amination by a crown ether

Synthetic study on the unique dimeric arylpiperazine: access to the minor contaminant of aripiprazole

The dimeric derivative of aripiprazole was synthesized via the two notable synthetic technologies as a key step: (1) efficient aldehyde bis-arylation by Bi(OTf)(3) and (2) facile Wynberg amination at room temperature. The synthesis has established the structural identity with the minor contaminant sometimes present in Aripiprazole.

Progress in arylpiperazine synthesis by the catalytic amination reaction

Careful base and solvent optimization for catalytic amination is described. A Pd-catalyzed amination between some arylbromide and unprotected piperazine (1equiv) was efficiently carried out with Pd/BINAP catalyst in a toluene-DBU solvent system, which is useful for the one-pot preparation of unsymmetrical piperazine through amination and in-situ N-protection. Reaction with N-BOC-piperazine was also successful in toluene-DBU or more polar NMP with Cs(2)CO(3) as a key base. No reports have previously reported such solvent and base optimization in arylpiperazine synthesis.

Some aspects of NaBH(4) reduction in NMP

In our solvent optimization study of NaBH(4) reduction, NMP was found to enhance the reactivity. A chemoselective debromination of the bromide and sulfonates can be attained in the new borohydride reagent system: NaBH(4)-LiOTf-NMP. This mixed system worked as an alternative to NaBH(3)CN and Bu(3)SnH for the S(N)2 type displacement of alkylbromide and sulfonate. Also mentioned is an expedient reduction of an azide group into amine by NaBH(4) in NMP without any additive, which offers a convenient protocol for the direct transformation of halides into amines via azide in one flask. Some examples of other reductions were also presented.

Beneficial effect of cesium salts on Pd-catalyzed hydroxycarbonylation

A Pd(0)-catalyzed hydroxycarbonylation of the aryl bromide was effectively carried out in the presence of some Cs salts such as cesium carbonate, cesium bicarbonate, and cesium acetate in wet DMF solution. For the understanding of their function, an oxy-coordinated intermediate arising from a Cs oxygen-Pd interaction has been postulated, which is likely to be responsible for related Cs assisted catalytic processes.