Palladium(II)-Promoted Cyclization Reaction of 4-Hydroxybutyronitrile to 2-Iminotetrahydrofuran. X-ray Structure of cis-[PdCl2{N(H)CCH2CH2CH2O}- (PPh3)]·1/2CH2Cl2
摘要:
Reaction of 3-bromo-1-propanol with Et(4)N(CN) in CN(?)2Cl(2) at room temperature gives in high yield 4-hydroxybutyronitrile, HO(CH2)(3)CN (1), which upon reaction with Na2PdCl4 affords [PdCl2{N(H)=CCH2CH2CH2O}(2)] (2), containing two 2-iminotetrahydrofuran ligands derived from intramolecular cyclization of 1. Substitution of one imino ligand for an entering nucleophile L leads to the complexes [PdCl2{N(H)=CCH2CH2CH2O}(L)] (L = PPh(3) (3), py (4), DMF (5)). Similarly, the reaction of 2 with 1 equiv of cis-PH2PCH=CHPPh(2) results in the displacement of the two iminolactone ligands and formation of [PdCl2(Ph(2)PCH=CHPPh(2))]. The ligand 1 and the complexes 2-5 were characterized by analytical and spectroscopic techniques. IR data suggest that 2 and 3 are present as a mixture of cis and trans isomers, while 4 and 5 have a trans stereochemistry. Complex 3 gave crystals of the cis form, as evidenced by an X-ray structural determination.