Versatile and Efficient Synthesis of a New Class of Aza-Based Phosphinic Amide Ligands via Unusual PC Cleavage
✍ Scribed by Shih-Chung Tsai; Yaw-Shien Fu; Ju-Hsiou Liao; Shuchun Joyce Yu
- Book ID
- 102253842
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- German
- Weight
- 135 KB
- Volume
- 89
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
A new class of bidentate, aza-based phosphinic amide ligands of the type RN(H)P(=O)(2-py) 2 (2py = 2-pyridyl) was synthesized within minutes via a one-pot process including Staudinger reaction of an organic azide (RN 3 ) with 2-pyridylphosphines, followed by partial, unprecedented hydrolysis under loss of one aromatic substituent. The structure of the unusual-hydrolysis product H 2 C=CH(CH 2 ) 9 -N(H)P(=O)(2-py) 2 (5a) was characterized by IR, 1 H-and 31 P-NMR, as well as by X-ray crystal-structure analysis (Figure). The tetrahedral P-atom was found to be surrounded by a trigonal-pyramidal arrangement of the substituents. To gain insight into the formation of these novel phosphinic amides, a series of intermediate iminophosphoranes, H 2 C=CH(CH 2 ) 9 N=P(Ar) n (2-py) 3 À n (n = 0 -3), compounds 1a -1f, were synthesized, and their hydrolyses were studied. All tested compounds followed the classical hydrolysis route of P=N cleavage under acidic conditions. Sequential hydrolysis to 5a -5d only occurred under either basic conditions or in wet MeCN as solvent. Notably, H 2 C=CH(CH 2 ) 9 N=P(C 6 H 5 )(4-MeO-2-py) 2 (1c) was hydrolyzed at a much slower rate compared to its analogue 1b lacking the MeO group. On the contrary, the halogenated compounds H 2 C=CH(CH 2 ) 9 N=P(4-X-C 6 H 4 ) 3 (1f,g) (X= F, Cl) were hydrolyzed at a notably faster rate relative to the non-halogenated congener 1e (X = H).