Formation of P-C Linkages

The synthesis of organophosphorus compounds at some stage involves the formation of P-C linkages. The best-known method of forming these linkages is by the Arbusov reaction (3.107, 6.342). Other synthetic methods worthy of note at this point include formation of phosphoranes (6.14), (6.15), (6.94) and so on, the use of organometallic compounds (6.16), (6.17), (6.38), (6.144), (6.207), (6.499) and so on, Friedel-Crafts-type reactions (6.18), and direct reactions with elemental P (6.19), 

Et4Pb + PCI3 EtPClj + EtjPbCl BujHg + 2PCI3 2BUPCI2 + HgCl2 

There has so far been only limited success in attempts to produce P-C compounds directly from elemental phosphorus, although both white and red forms are subject to attack by a variety of nucleophilic reagents. These and other synthetic methods are discussed below in this chapter. Synthesis of P-C bonds has recently been comprehensively reviewed [21]. The synthesis of P=C and P=C bonds is dealt with in Sections 6.14 and 6.15 (see also Phospha-Wittig reaction (6.445)). Carbophosphenes can be obtained from carbophosphynes and vice versa (6.631,6.631a), although these are not general methods of preparation. 

The first synthesis of an organophosphine was probably carried out by Thenard in 1845 [13]. 

Organophosphines (6.21), like most trivalent phosphorus compounds, are usually very reactive substances. They are strongly nucleophilic - more so than the corresponding amines. Many organophosphines possess an unpleasant odour similar to that of parent phosphine, PHj itself, and they are rather toxic, particularly the lower members which are liquids at room temperature. AU phosphines are subject to oxidation and the simple mono and di alkylphosphines have a great affinity for atmospheric oxygen. Trimethylphosphine vapour is spontaneously inflammable in air. 

---