Preparation of Bicyclic Secondary and Tertiary Phosphines from Radical Addition of Phosphine and Primary Phosphines to Limonene

Abstract

In the presence of a free radical initiator, limonene combines with a primary phosphine to yield a 1:1 adduct (I). Initially the addition takes place at the isopropenyl moiety. The resulting secondary phosphine subsequently undergoes an intramolecular addition to produce two isomeric 2-alkyl-4,8-dimethyl-3-phosphabicyclo [3.3.1]nonanes (II, III) in >85% yield. Analogous bicyclic secondary phosphines are formed by free radical addition of phosphine to limonene. Yields are slightly lower due to the addition of the reactive secondary phosphines to a second mole of limonene.