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)(2)](2)[Cp*Fe(η(4)-P(5))] (I) in combination with α,ω-dibromoalkanes C(n)H(2n)Br(2) [n = 3–6], unique phosphetane, phospholane, phosphinane and phosphepane precursor complexes [Cp*Fe{η(4)-P(5)(CH(2))(n)}] [n = 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 i.e., potassium benzyl (KBn) or LiAlH(4). The latter enables the selective synthesis of parent cyclic secondary phosphines (10) in an easy and straightforward way, including the first parent phospholane (10b).