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 2 n 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).