Concise asymmetric synthesis of (−)-halosaline and (2R,9aR)-(+)-2-hydroxy-quinolizidine by ruthenium-catalyzed ring-rearrangement metathesis

A ruthenium-catalyzed ring opening-ring closing metathesis reaction serves as the key step in the stereoselective synthesis of a new enantiopure 2-substituted-4,5-dehydropiperidine skeleton, a valuable intermediate for the synthesis of piperidine alkaloids (such as (−)-halosaline) and of hydroxylated quinolizidines (such as (2R,9aR)-(+)-2-hydroxy-quinolizidine).     

Deuterated ammonium formate as deuterium source in a mild catalytic deuterium transfer reaction of pyridines, pyrazines and isoquinolines

The application of deuterated ammonium formate as deuterium source in transfer deuteration reactions of aromatic heterocycles (4-6) for the synthesis of highly deuterated, substituted piperidines (1), piperazines (2) and tetrahydroisoquinolines (3) has been developed.     

An infrared and Raman spectroscopic study of the Hofmann-type complexes and clathrates: M(piperidine)2Ni(CN)4; M(piperidine)2Ni(CN)4·1.5G (M=Cd, Co, Ni or Cu; G=benzene)

New Hofmann-type complexes and clathrates of the forms M(piperidine)₂Ni(CN)₄ and M(piperidine)₂Ni(CN)₄·1.5G (M=Cd, Co, Ni or Cu; G=benzene) were prepared in powder form and their infrared and Raman spectra are reported. The spectral features suggest that these compounds are similar in structure to the Hofmann-type clathrates except for the copper compounds. The complex and clathrate of Cu have different spectral features in comparison with its analogues due to the Jahn-Teller effect.     

Characterization and crystal structures of copper(II), cobalt(II), and nickel(II) complexes with two kinds of piperidine carboxylic acids

Copper(II) complex with -piperidine-3-carboxylic acid ( -Hpipe-3):[Cu( -pipe-3)₂(H₂O)] and cobalt(II) and nickel(II) complexes with piperidine-4-carboxylic acid (Hpipe-4):[M(Hpipe-4)₂(H₂O)₄]Cl₂ (M: Co, Ni) have been prepared and characterized by means of IR and powder diffuse reflection spectra, thermal analysis, and magnetic susceptibility. The crystal structures of these complexes have been determined by X-ray diffraction. The crystal of [Cu( -pipe-3)₂(H₂O)] is orthorhombic with the space group Pbcn. The copper atom is in a square pyramidal geometry, ligated by two carboxylato oxygen atoms, two nitrogen atoms, and a water molecule. One molecule of this complex consists of either -piperidine-3-carboxylic acid or -piperidine-3-carboxylic acid. The crystals of [M(Hpipe-4)₂(H₂O)₄]Cl₂ are monoclinic with space group P2₁/n. In these complexes the metal atom is in an octahedral geometry ligated by two carboxylato oxygen atoms and four water molecules.     

Adsorption of oligooxypropylenated amines at the aqueous solution—air interface: Homologous series of piperidine and morpholine derivatives

The surface tension isotherms for pure oligooxypropylenated piperidine and morpholine at the aqueous solution—air interface were determined and interpreted. The surface excess concentration, Γ, the surface area per molecule, A, and the standard free energy of adsorption, ΔG°, were calculated according to a new empirical adsorption equation. The standard free energy contribution for the oxypropylene group (PO) in morpholine derivatives,ΔG° (PO) = −3.34 kJ mol⁻¹, is substantially lower than that for the PO group located in the piperidine derivatives, i.e. ΔG° (PO)= −3.12 kJ mol⁻¹.     

Synthesis of 3,4-disubstituted piperidines by ene cyclisation of 4-aza-1,7-dienes

Ene cyclisation of a variety of 4-aza-1,7-dienes affords 3,4-disubstituted piperidines. In particular, cyclisation of diesters 14 and 20 catalysed by MeAlCl₂ gives the corresponding trans 3,4-disubstituted piperidines with diastereomeric ratios of >200:1.     

Solvent Free Synthesis of Coumarins

An efficient synthesis of 3-substituted coumarins under solventless system is described.     

N,S-Substituted Dienes from Mono(arylthio)substituted- and S-, S,S-Substituted Dienes

Mono(thio)substituted dienes 1a-1b gave compounds 3a-c and 5d-g with piperazine and piperidine derivatives in dichloromethane. Compounds 8 , 9 , and 10 were obtained from the reactions of perchlorobutadiene ( 6 ) with 1,4-butanedithiol ( 7 ) in ethanol in the presence of sodium hydroxide. Compounds 12a-b , 13a-b were obtained from the reactions of perchlorobutadiene ( 6 ) with allylmercaptan (CH 2 =CH--CH 2 --SH) and mercaptoethanol (HO--CH 2 --CH 2 --SH).