ChemInform Abstract: Synthesis of Hemilabile P,N Ligands: ω-2-Pyridyl-n-alkylphosphines

A series of P,N ligands of the general formula (2-py)-(CH2) n -PR 2 (2-py: 2-pyridyl; R: i-Pr (n=1, 4–7), Ph (n=5–7)) 4a–g and 6a has been synthesized. Starting from 2-picoline (1), 2-(ω-chloroalkyl)pyridines 3a–d are prepared. The reactions of 3a–d with (i-Pr)2PLi and Ph2PLi, respectively, result in the title compounds 4a–g in up to 89% yield. Reaction of Cl-(CH2)3-P(i-Pr)2 with 2-picolyllithium (2) is an alternative route to 4a. Additionally, P,P,N ligands 7a and 9 are synthesized by similar methods. All new compounds were fully characterized. The formation of cyclic pyridinium derivatives 5a and 5b from intramolecular S N reactions of 3a and 3b is discussed in detail.