Roger Crossley

Synthesis and properties of a potential extracellular fluorescent probe for potassium

Development of a new, selective, high affinity, fluorescent probe CD222, 2, for potassium is described. Coincidentally two related probes, CDF18, 3, and CTF18, 4, were prepared and showed selectivity for the cations sodium and calcium, respectively, and possible reasons for these differences are discussed. The bicyclic probe CD222, 2, with observed KD values for K+ ranging from 1 to 10 mmol dm–3, has potential applications as an extracellular probe for potassium.

Synthesis and spectral properties of new fluorescent probes for potassium

Studies on the preparation and properties of two new, selective fluorescent probes CD18, 1 and C18, 2 for potassium are described. The probes incorporate the 1,10-diaza-18-crown-6 chelating group for the ion and the coumarin group as the fluorophore. The probes are compared with the known reagent PBFI. CD18 shows considerably greater selectivity for potassium over sodium than PBFI.

A novel synthesis of thiols from α-amino-nitriles

Reaction of α-alkylamino-nitriles [R1R2C(NHR3)CN] with hydrogen sulphide under mild conditions gives high yields of thiols (R1R2CHSH) with none of the anticipated α-amino-thioamides. Under the same conditions the parent aldehydes, thioaldehydes, and corresponding imines give only mixtures of polysulphides.

5,6,7,8-Tetrahydroquinolines. Part 6. Silylation vs. Thioamidation in the reaction of silyl isothiocyanates with organometallics: influence of the solvent and of the substituents on silicon.

The influence of a number of variables on carbophilic vs. silicophilic attack by 8-lithio-3-methyl-5,6,7,8-tetrahydroquinoline on silyl isothiocyanates is reported. In general carbophilic attack (i.e. thiomidation) is favoured in solvents of low polarity and by bulky and/or electron-donating substituents on silicon. Preliminary blockage of the 8-position with a trimethylsilyl group leads to improved yields as a consequence of the suppression of a yield-limiting proton transfer. A mechanism is proposed for the formation of nitriles in the presence of an excess of reagent.

5,6,7,8-Tetrahydroquinolines. Part 7. Synthesis of 8-cyano-5,6,7,8-tetrahydroquinolines; di-isopropylcyanamide, a new reagent for cyanation of organometallics

Di-isopropylcyanamide (1) is an effective reagent for the conversion of 8-lithio-5,6,7,8-tetra-hydroquinolines into 8-cyano-5,6,7,8-tetrahydroquinolines. 8,8-Dicyano derivatives are not formed. A convenient synthesis of the reagent from disodium cyanamide is described.

5,6,7,8-Tetrahydroquinolines. Part II. Preparation and reactions of substituted 5,6,7,8-tetrahydroquinoline-8-carboxylic esters

A series of substituted 5,6,7,8-tetrahydroquinoline-8-carboxylic esters have been prepared by the reaction of the 8-lithio- and 8-magnesio-derivatives of 5,6,7,8-tetrahydroquinolines with carbon dioxide followed by esterification. The esters were converted into the corresponding amides, nitriles, and thioamides.