TY - JOUR

T1 - PtII-mediated 1,3-dipolar cycloaddition of oxazoline N-oxides to nitriles as a key step to dihydrooxazolo-1,2,4-oxadiazoles

AU - Makarycheva-Mikhailova, Anastassiya V.

AU - Golenetskaya, Julia A.

AU - Bokach, Nadezhda A.

AU - Balova, Irina A.

AU - Haukka, Matti

AU - Kukushkin, Vadim Yu

PY - 2007/10/1

Y1 - 2007/10/1

N2 - A novel type of heterocycle, viz., 2,3a-disubstituted 5,6-dihydro-3aH-[1,3] oxazolo[3,2-b][1,2,4]oxadiazoles, was generated by an intermolecular Remediated 1,3-dipolar cycloaddition (1,3-DCA) between the oxazoline N-oxide C(Me) 2CH2OC(R)=N+(O-) (R = Me, Et) and coordinated nitriles in the complexes trans/cis-[PtCl2(R′CN) 2] [R′ = Me, Et, CH2Ph, Ph, N(C5H 10)]. The reaction is unknown for free RCN and oxazoline N-oxides, but under Remediated conditions, it proceeds smoothly (CH2Cl 2, 20-25°C, 18-20 h) and gives pure complexes [PtCl 2{N=C(R′)ONC(R)OCH2CMe2}2] [R/R′ = Me/Me, 1; Me/Et, 2; Me/CH2Ph, 3; Me/Ph, 4; Me/N(C 5H10), 5; Et/Me, 6; Et/Et, 7; Et/CH2Ph, 8; Et/Ph, 9; Et/N(C5H10), 10] in 42-84% yields after column chromatography. Compounds 1-10 were characterized by elemental analyses (C, H, N), FAB+-MS, IR, and 1H and 13C{1H} NMR spectroscopies, and X-ray diffraction (for 1, 2, 5, and 9). With the exception of benzonitrile complexes, 1,3-DCA of oxazoline N-oxides to the PtII-ligated nitriles occurred diastereoselectively and afforded mixtures of enantiomers. Depending on the substituents on nitriles, asymmetric atoms in both of the formed heterocyclic ligands have the same (SS/ RR) or different (SR/RS) configurations. The heterocyclic ligands were liberated from 1-4 and 6-9 by treatment with excess ethane-1,2-diamine (en) in CH 2Cl2 for 1 day at 20-25°C (for R′ = Me, Et, CH2Ph) and at 50°C (for R′ = Ph) to achieve the free organic species and the well-known [Pt(en)2](Cl)2; the products were separated, and 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3, 2-b][1,2,4]oxadiazoles (11-18) were characterized by ESI+-MS and 1H and 13C{1H} NMR spectroscopies.

AB - A novel type of heterocycle, viz., 2,3a-disubstituted 5,6-dihydro-3aH-[1,3] oxazolo[3,2-b][1,2,4]oxadiazoles, was generated by an intermolecular Remediated 1,3-dipolar cycloaddition (1,3-DCA) between the oxazoline N-oxide C(Me) 2CH2OC(R)=N+(O-) (R = Me, Et) and coordinated nitriles in the complexes trans/cis-[PtCl2(R′CN) 2] [R′ = Me, Et, CH2Ph, Ph, N(C5H 10)]. The reaction is unknown for free RCN and oxazoline N-oxides, but under Remediated conditions, it proceeds smoothly (CH2Cl 2, 20-25°C, 18-20 h) and gives pure complexes [PtCl 2{N=C(R′)ONC(R)OCH2CMe2}2] [R/R′ = Me/Me, 1; Me/Et, 2; Me/CH2Ph, 3; Me/Ph, 4; Me/N(C 5H10), 5; Et/Me, 6; Et/Et, 7; Et/CH2Ph, 8; Et/Ph, 9; Et/N(C5H10), 10] in 42-84% yields after column chromatography. Compounds 1-10 were characterized by elemental analyses (C, H, N), FAB+-MS, IR, and 1H and 13C{1H} NMR spectroscopies, and X-ray diffraction (for 1, 2, 5, and 9). With the exception of benzonitrile complexes, 1,3-DCA of oxazoline N-oxides to the PtII-ligated nitriles occurred diastereoselectively and afforded mixtures of enantiomers. Depending on the substituents on nitriles, asymmetric atoms in both of the formed heterocyclic ligands have the same (SS/ RR) or different (SR/RS) configurations. The heterocyclic ligands were liberated from 1-4 and 6-9 by treatment with excess ethane-1,2-diamine (en) in CH 2Cl2 for 1 day at 20-25°C (for R′ = Me, Et, CH2Ph) and at 50°C (for R′ = Ph) to achieve the free organic species and the well-known [Pt(en)2](Cl)2; the products were separated, and 2,3a-disubstituted 5,6-dihydro-3aH-[1,3]oxazolo[3, 2-b][1,2,4]oxadiazoles (11-18) were characterized by ESI+-MS and 1H and 13C{1H} NMR spectroscopies.

UR - http://www.scopus.com/inward/record.url?scp=35348926869&partnerID=8YFLogxK

U2 - 10.1021/ic701133b

DO - 10.1021/ic701133b

M3 - Article

AN - SCOPUS:35348926869

VL - 46

SP - 8323

EP - 8331

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 20

ER -