Dihalo phosphines, synthesis

Other sources of Ru(0) can also be used for this synthesis. For example, it was recently demonstrated that [Ru(arene)(diene)] complexes such as 39 undergo double oxidative addition of heterosubstituted dihalo compounds 40 in the presence of phosphine ligands (Eq. 5) [21]. 

The most direct synthesis is performed by reaction of a dihalo compound with a tricoordinated phosphorus compound including a reactive P—Y bond (reaction 101). This synthesis, first used with secondary phosphines, the corresponding phosphides or diphosphines (Y = H, Na, K, PPh2)2b,38°, has subsequently been developed also with silylphosphines (Y = SiMe3),132,381-383 which are easier to handle (reaction 102). The same kind of cyclization by intramolecular alkylation can be achieved using a functional phosphine prepared in a multi-step synthesis380,384,385 (reaction 103). 

The dithienophospholes 74 are obtained in good yields by lithiation of dibromo-bithiophenes 73, followed by addition of dihalo (aryl) phosphines (Scheme 4.22) [57]. The Lewis basicity of the P center of 74 enables a broad range of facile chemical modifications to be undertaken, as exemplified with the synthesis of derivatives 75-77 (Scheme 4.22) [57]. 

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