Rapid and efficient synthesis of 1-arylpiperazines under microwave irradiation

Pd-Catalyzed Synthesis of Piperazine Scaffolds Under Aerobic and Solvent-Free Conditions

A facile Pd-catalyzed methodology providing an efficient synthetic route to biologically relevant arylpiperazines under aerobic conditions is reported. Electron donating and sterically hindered aryl chlorides were aminated to afford yields up to 97%, with examples using piperazine as solvent, illustrating an ecofriendly, cost-effective synthesis of these privileged structures.

A versatile and practical microwave-assisted synthesis of sterically hindered N-arylpiperazines

A wide-ranging and practical synthesis of structurally diverse, sterically hindered N-arylpiperazines from 2,2'-(4-nitrophenylsulfonylazanediyl) bis(ethane-2,1-diyl) bis(4-nitrobenzenesulfonate) and substituted anilines has been achieved using microwave irradiation in acetonitrile followed by deprotection with PhSH.

Microwave-mediated synthesis of labeled nucleotides with utility in the synthesis of DNA probes

A novel method of linking haptens to deoxycytidine 5'-triphosphate via microwave-mediated bisulfate-catalyzed transamination with hydrazine has been developed. This method enables the tethering of small molecule haptens to dCTP via a discrete polyethylene glycol (PEG) spacer, yielding N(4)-aminodeoxycytidine 5'-triphosphate-dPEG-haptens. This synthetic approach employs microwave-catalyzed hydrazinolysis that enables the attachment of spacers via hydrazine linkages. The microwave-mediated introduction of this hydrazine handle provides a significant improvement in yield over those of published thermal methods. The microwave reaction was shown to be scalable, and the final product was amenable to labeling with a wide variety of haptens. The resulting nucleotide triphosphates, N(4)-aminodeoxycytidine 5'-triphosphate-dPEG-haptens, can serve as unique substrates for the enzyme-mediated labeling of DNA probes. The efficacy of incorporation of one such novel nucleotide, N(4)-aminodeoxycytidine 5'-triphosphate-dPEG(4)-DNP, has been demonstrated in nick translation labeling of HER2 and HPV probes. The labeled probes have been shown to be effective in visualizing their target genes in tissue.

Design of Potent, Orally Available Antagonists of the Transient Receptor Potential Vanilloid 1. Structure−Activity Relationships of 2-Piperazin-1-yl-1H-benzimidazoles

The vanilloid receptor-1 (VR1 or TRPV1) is a membrane-bound, nonselective cation channel that is predominantly expressed by peripheral neurons sensing painful stimuli. TRPV1 antagonists produce antihyperalgesic effects in animal models of inflammatory and neuropathic pain. Herein, we describe the synthesis and the structure-activity relationships of a series of 2-(4-pyridin-2-ylpiperazin-1-yl)-1H-benzo[d]imidazoles as novel TRPV1 antagonists. Compound 46ad was among the most potent analogues in this series. This compound was orally bioavailable in rats and was efficacious in blocking capsaicin-induced flinch in rats in a dose-dependent manner. Compound 46ad also reversed thermal hyperalgesia in a model of inflammatory pain, which was induced by complete Freund's adjuvant (CFA).

Iron-assisted nucleophilic aromatic substitution on solid phase

Iron-assisted S(N)Ar reactions were performed for the first time on solid phase, and a library of 36 unsymmetrically substituted phenylpiperazines and phenyl-1,4-diazepanes was synthesized with this novel strategy. The scope of iron-assisted S(N)Ar reactions on solid phase was investigated, and reactions of representative nucleophiles from groups VI (O, S, and Se) and V (N and P) of the periodic table were examined. Decomplexation of resin-bound iron complexes was achieved with 1,10-phenanthroline under irradiation, thereby overcoming the notorious disadvantages of decomplexation observed in solution-phase chemistry.