Formation of P−C Bonds under Unexpectedly Mild Conditions. Phosphoryl Migration and Metal Coordination of Diphenylphosphinomethyl-oxazolines and -thiazolines

Abstract

The heterocycles 2-methyl-2-oxazoline (mox) and 2-methyl-2-thiazoline (mth) react with Ph2PCl under mild conditions, in the presence of NEt3 which promotes their phosphorylation by stabilization of their enamino tautomers moxe and mthe, respectively, and which also behaves as HCl scavenger. Depending on the reaction conditions, three different phosphine ligands were obtained in good yields from mox: the monophosphine Ph2PCH2CNCH2CH2O (1ox) and the isomeric diphosphines Ph2PCHCOCH2CH2NPPh2 (2ox) (X-ray structure) and (Ph2P)2CHCNCH2CH2O (3ox). The formation of these ligands involves phosphoryl migration reactions, which were studied by NMR spectroscopy. The synthesis and the X-ray structures of the corresponding diphenylphosphinothiazolines Ph2PCH2CNCH2CH2S (1th) and Ph2CHCSCH2CH2NPPh2 (2th) are also reported but the thiazoline analog of the geminal diphosphine 3ox was not observed. The metal complexes [Pt(3ox-H)2]·4CH2Cl2 (4·4CH2Cl2), [Pt(Me)I(1ox)] (5), [Pt(Me)2(1ox)] (7), [Pd(dmba-C,N)(1th)]OTf·0.25Et2O (8·0.25Et2O), [Pd(dmba-C,N)(1th-H)] (9), and [9·{Pd(dmba-C,N)Cl}]·2.5C6H6 (10·2.5C6H6) have been prepared and structurally characterized by X-ray diffraction