Novel Synthetic Route for (parent) Phosphetanes, Phospholanes, Phosphinanes and Phosphepanes

A novel synthetic route for (parent) phosphorus-containing cycloalkanes such as phosphetanes, phospholanes, phosphinanes and phosphepanes is reported. By using [K(dme)][Cp*Fe(η-P)] (I) in combination with α,ω-dibromoalkanes C H Br [ = 3-6], unique phosphetane, phospholane, phosphinane and phosphepane precursor complexes [Cp*Fe{η-P(CH) }] [ = 3-6] (2-5) are synthesised. They act as P-atom carriers and the corresponding phosphetane, phospholane, phosphinane and phosphepanes (6-9) can be released by nucleophiles , potassium benzyl (KBn) or LiAlH. The latter enables the selective synthesis of parent cyclic secondary phosphines (10) in an easy and straightforward way, including the first parent phospholane (10b).