Fred Capretta: Research Interests

Synthesis and Structure of Alkylphosphines and Their Use as Ligands in Catalysis

Novel Chiral Phosphines Derived From Terpenes

In conjunction with colleagues at Cytec Canada Inc.,  a modification of the established protocol for the preparation of phosphines involving the free radical addition of PH3 to alkenes has been carried out using unsaturated terpenes as the olefin source. For example, two successive additions of a single PH3 to limonene resulted in the facile synthesis of the secondary phosphine 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonane. 

The compound has been characterized by x-ray crystallographic analyses of its oxidation products, 2-(4-methylcyclohexyl)propylphosphonic acid and 4,8-dimethyl-2-phosphabicyclo[3.3.1]nonan-2-ol-oxide.  This base structure can be arylated at the P atom allowing for a fine tuning of the electronic and structural features of the phosphorane.  We are broadening the scope of this terpene/PH3 adduct work and examine the application of the phosphinyl radical addition methodology to other terpenes (such as camphene and carvone) as well as looking at the employment of various mono- and dialkyl substituted phosphines thereby expanding the structural diversity available.  Modification of the reaction conditions in order to allow for more stereocontrol in the radical additions reaction is also being investigated.

Reference: A. Robertson, C. Bradaric, C. S. Frampton, J. McNulty, and A. Capretta. Tetrahedron Letters.2001, 42, 2609.