Author/Authors :
Pombeiro، Armando J. L. نويسنده , , Haukka، Matti نويسنده , , Kukushkin، Vadim Yu. نويسنده , , Nazarov، Alexey A. نويسنده , , Galanski، Markus نويسنده , , Keppler، Bernhard K. نويسنده , , Makarycheva-Mikhailova، Anastassiya V. نويسنده , , Garnovskii، Dmitrii A. نويسنده ,
Abstract :
The reaction between the platinum(IV) complex trans-[PtCl4(EtCN)2] and the amino alcohols NH2CH2CH20H, NH2CH2CH(Me)OH-(R)-(-), NH2CH(Ph)CH20H-(R)-(-), NH2CH(Et)CH20H-(R)-(-), NH2CH(Et)CH20H-(S)-(+), and NH2CH(Pr^nCH2OH proceeds rapidly at room temperature in CH2Cl2 to furnish the amidine complexes [PtCl4{HN=C(Et)NH OH}2] (1-6) in good yield (70-80%). The related reaction between the platinum(ll) complex trans[PtCl2(EtCN)2] and monoethanolamine in a molar ratio of 1:2 in CH2Cl2 results in the addition of 4 equiv of NH2CH2CH20H per mole of complex to give [Pt{HN==C(Et)NHCH2CH2cHoh}2(NH2CH2CH2oH)2]^2+ (7). Formulation of 1-6 is based upon satisfactory C, H, N elemental analyses, electrospray mass spectrometry, IR spectroscopy, and 1H, 13C{1H}, 15N, and 195Pt NMR spectroscopies, while the structures of trans-[PtCl4{(Z)-NH=C(Et)NHCH2CH2OH}2] (1), trans-[PtCl4{(Z)-NH=C(Et)NHCH2CH(Me)OH-(R)-(-)}2] (2), and trans-[PtCl4{(Z)-NH=C(Et)NHCH(Et)CH2OH-(R)-(-)}2] (4) were determined by X-ray single-crystal diffraction. The Z-amidine configuration of the ligands is preserved in CDCls solutions as confirmed by gradient-enhanced 15N,1H-HMQC spectroscopy and NOE experiments. The amidines, formed upon Pt(IV)-mediated nitrile-amino alcohol coupling, were liberated from their platinum(IV) complexes 1, 3, and 4 by reaction with Ph2PCH2CH2PPh2 (dppe) giving free NH=C(Et)NHCHRCH20H (R-H 8, Et 9, Ph 10), with the substituents R of different types, and dppe oxides; the P-containing species were identified by 31P{1H} NMR spectroscopy. NOESY spectroscopy indicates that the liberated amidines retained the same configuration relative to the C=N double bond, i.e., syn-(H,Et)-NH=C(Et)NHCHRCH20H. The liberated hydroxofunctionalized amidines 8-10 were converted into oxazolines N=C(Et)OCH2CH(R) (11-13) in the presence of a catalytic amount of ZnCl2 A similar catalytic effect has also been reached using anhydrous MS04 (M = Cu, Co, Cd), CdCl2, and AlCIs.
