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Upstream product

• 36884-28-3 5-phenyl-1-pentanal 
• 126613-22-7 5-Phenylpentanal dimethyl acetal 
• 75553-23-0 (E)-5-phenyl-2-penten-1-ol 

Relevant academic research and scientific papers

Non-imidazole histamine H3 ligands. Part VI. Synthesis and preliminary pharmacological investigation of thiazole-type histamine H3-receptor antagonists with lacking a nitrogen nucleus in the side chain

Background: Antagonists to the H3 receptor are considered to be potential drugs for the treatment of Alzheimer's disease, attention deficit-hyperactive disorder, memory and learning deficits, and epilepsy. The initial development of potent H3 receptor antagonists focused on extensive modification of the natural ligand histamine. However, it has appeared that imidazole-containing ligands are associated with inhibition of cytochrome P450 enzymes, caused by imidazole nitrogen complexation to heme iron in the active site of the enzyme. For these reasons, the development of potent non-imidazole H3 receptor antagonists was eagerly awaited. Objective: Previously, we reported the synthesis and pharmacological in vitro characterization of series of potent histamine H3-receptor non-imidazole antagonists belonging to the class of substituted 2-thiazol-4-n-propylpiperazines. A lead compound 1 of this family was a derivative carrying the ethylaminomethylpropyl chain. Methods: With the aim of increasing lipophilicity, that will help the ligands to cross the blood-brain barrier, we synthesized a series of new 2-thiazol-4-n-propylpiperazines where the ethylaminomethylpropyl moiety was replaced by a p-substituted-, an unsubstituted benzene ring, and ω-phenylalkyl substituent at positions 4 and 5 of thiazole ring, respectively. All compounds were tested for H3 antagonistic effects in vitro using the electrically contracting guinea pig jejunum. Results: The most active compounds of presented series 3d, 3e, and 3j showed lower affinity than the lead compound 1 and additionally, derivatives 3d and 3j possessed weak, competitive H1-antagonistic activity. This is in contrast to the lead compound 1 that has no affinity at H1 receptor. Conclusion: We can conclude that a side chain in the 2-thiazol-4-n-propylpiperazine scaffold should contain a basic center and should be present at a favorable position 5 of thiazole ring.

Iridium-catalyzed isomerization/bromination of allylic alcohols: Synthesis of α-bromocarbonyl compounds

α-Brominated ketones and aldehydes, with two adjacent electrophilic carbon atoms, are highly valuable synthetic intermediates in organic synthesis, however, their synthesis from unsymmetrical ketones is very challenging, and current methods suffer from low selectivity. We present a new, reliable, and efficient method for the synthesis of α-bromocarbonyl compounds in excellent yields and with excellent selectivities. Starting from allylic alcohols as the carbonyl precursors, the combination of a 1,3-hydrogen shift catalyzed by iridium(III) with an electrophilic bromination gives α-bromoketones and aldehydes in good to excellent yields. The selectivity of the process is determined by the structure of the starting allylic alcohol; thus, α-bromoketones formally derived from unsymmetrical ketones can be synthesized in a straightforward and selective manner. Synthon shuffle: An efficient and high-yielding synthetic route to prepare α-bromoketones and aldehydes is presented (see scheme, Cp=pentamethylcyclopentadienyl). The method relies on 1,3-hydrogen shift/bromination of allylic alcohols catalyzed by IrIII complexes. The products are obtained in excellent yields and as single constitutional isomers.