P-H as Key Functional Group

Similarly to the P-CHj group, secondary phosphine-boranes react smoothly in the presence of a base (BuLi, NaH) under mild conditions to afford other kinds of functionalized phosphine-boranes in good to high yields, without racemi-zation. Yet the success of deprotonation/treatment with an electrophile process to afford substituted phosphine derivatives without any loss in optical purity may depend on the deprotonation agents employed. Use of butyllithium usually provides the products with high enantiomeric excess in good to high yields [73]. 

As mentioned in Sect. 3.1.1, secondary phosphine-boranes also react efficiently with aryl iodides in palladium-catalyzed substitution reactions (Pd(PPh3)4) [73]. In all cases the boranato functional group remains unchanged. 

Base-promoted deformylation (KOH/A) to afford the same secondary phos-phine-boranes is less effective and an acceptable compromise between yield and selectivity is difficult to reach. When the reaction proceeds smoothly, it is accompanied by significant racemization [93]. 

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