Reaction of 4-hydrazinoquinolines with β-diketones. Synthesis and spectroscopy (1h, 13c nmr,ms) of some pyrazolylquinolines

A series of 4-pyrazolylquinolines have been prepared from 4-hydrazinoquinolines and β-dicarbonyl compounds and the previously proposed diazepine structure for the reaction products has been ruled out. A ¹³C nmr study established the 3-position of the methyl group when two isomers were possible. Finally, a careful ¹H nmr study of 2- and 4-pyrazolylquinolines led to the conclusion that intramolecular hydrogen bonds between aromatic (or heteroaromatic) C-H and pyridine like nitrogens is the factor that determines the conformation of these compounds.     

Isolation and characterization of phenyl viologen as a radical cation and neutral molecule

The chemical synthesis, isolation, and characterization of phenyl viologen (PV) as a dication, radical cation, and neutral species are described. Single-crystal X-ray diffraction of PV(2+)2Cl(-.)2H2O and PV(.+)PF(6)(-).pyridine reveals the expected differences in bond lengths and also a structural change from two coplanar central rings in PV(.+) to a twist of 36 degrees between the two central rings in PV(2+). The phenyl viologen radical cation exhibits behavior characteristic of many radical cations, including weak pi-dimerization in the solid state and reversible pi-dimerization in solution. Electrical conductivity measurements of neutral phenyl viologen, the first such measurements of a neutral viologen, reveal that it is a significantly better conductor than the radical cation. Differences in geometric relaxation during charge transfer offer a possible explanation for the higher conductivity of the neutral viologen.     

Hypervalent iodine oxidation of amines using iodosobenzene: Synthesis of nitriles, ketones and lactams

Primary aliphatic amines on oxidation with iodosobenzene in CH₂Cl₂ or H₂O yield the corresponding nitriles, while primary cycloalkylamines give the corresponding cyclic ketones. Lactams are obtained by the oxidation of cyclic amines. (S)(−) Nicotine ( ) is oxidized to ( )-cotinine ( ). The intermediary imine involved in these processes was trapped in the case of piperidine as the -aminonitrile.     

An antiaromatic porphyrin complex: tetraphenylporphyrinato(silicon)(L)2 (L=THF or pyridine)

Treatment of Si(TPP)Cl2 (TPP = tetraphenylporphyrinato) with 2 equiv of Na/Hg in THF yields the reduced porphyrin complex, Si(TPP)(THF)2, in which the porphyrin ring system has an oxidation state of 4- and the complex is antiaromatic. Single-crystal X-ray diffraction reveals that Si(TPP)(THF)2 is highly ruffled and exhibits a unique C-C bond length alternation around its periphery. In addition, experimental 1H and 29Si NMR chemical shifts and NICS (nucleus-independent chemical shift) calculations on a model compound indicate a strong paratropic ring current in Si(TPP).     

Germanium phthalocyanine, GePc, and the reduced complexes SiPc(pyridine)(2) and GePc(pyridine)(2) containing antiaromatic pi-electron circuits

The reaction of GeCl2(dioxane) with K2Pc(DMF)4 yields germanium phthalocyanine, GePc. GePc dissolves in pyridine to form GePc(py)2. The 1H NMR spectrum of GePc(py)2 and nucleus-independent chemical shift (NICS) calculations on GePc(NMe3)2 both show the presence of a strong paratropic ring current. That ring current, along with the bond-length alternation in the crystal structure of GePc(tBuPy)2, indicates the presence of an antiaromatic pi-electron circuit in GePc(py)2. SiPc(py)2 was synthesized, and its electronic structure is similar to that of GePc(py)2.