Expedient synthesis of 3-phenylbicyclo[1.1.1]pentan-1-amine via metal-free homolytic aromatic alkylation of benzene

The inquisitiveness on the use of the BCP motif as a modern lead optimization tactic entails reliable synthetic access. In that direction, we disclose a new and versatile approach to 3-phenylbicyclo[1.1.1]pentan-1-amine, via metal-free homolytic alkylation of benzene.

New Hydrophobicity Constants of Substituents in Pyrazine Rings Derived from RP-HPLC Study

Pyrazine derivatives show a wide range of biological activities. 1-Pyrazin-2-ylethan-1-ones have served as food flavourants, and together with pyrazine-2-carbonitriles have been widely used as intermediates in the synthesis of various heterocyclic compounds. In our laboratory, substituted pyrazine-2-carbonitriles and 1-pyrazin-2-ylethan-1-ones have been used as intermediates for the preparation of potential antifungal and antimycobacterial drugs. Using established methods, a library of pyrazine derivatives was synthesized. Homolytic alkylation of commercially available pyrazine-2-carbonitrile yielded a series of 5-alkylpyrazine-2-carbonitriles which were converted into the corresponding 1-(5-alkylpyrazin-2-yl)ethan-1-ones (5-alkyl-2-acetylpyrazines) via the Grignard reaction. Homolytic acetylation of pyrazine-2-carbonitrile yielded 5-acetylpyrazine-2-carbonitrile. Using the same procedure, 3-acetyl-5-tert-butylpyrazine-2-carbonitrile was obtained with 5-tert-butylpyrazine-2-carbonitrile as a starting material. The hydrophobicity of the compounds was determined both experimentally (RP-HPLC) and by computation (CS ChemOffice Ultra version 9.0, ACD/LogP version 1.0 and ACD/LogP version 9.04), and both the approaches were compared. New hydrophobicity constants π based on experimental results were derived. These constants are markedly different from tabulated constants π valid for benzene rings, and can be widely used in estimating physicochemical properties of new biologically active pyrazines.

Synthesis of Some Anilides of 2-Alkyl-4-pyridinecarboxylic Acids and Their Photosynthesis-Inhibiting Activity

Homolytic alkylation of 4-pyridinecarbonitrile with radicals generated by silver nitrate catalyzed oxidative decarboxylation of alkanoic acids and subsequent alkaline hydrolysis afforded 2-alkyl-4-pyridinecarboxylic acids 2a-2e. These were converted into the halogeno-hydroxy substituted anilides 3a-3r via acyl chlorides by reaction with the respective aminophenols at 10 °C. Of the compounds tested, 5-chloro-2-hydroxyphenylamide of 2-butyl-4-pyridinecarboxylic acid 3h showed the highest effect upon oxygen evolution rate in spinach chloroplasts system. The structure-photosynthesis-inhibiting activity relationships are briefly discussed.