Menthol boranes

Many of the secondary phosphine boranes obtained with the menthol methodology have been deprotonated (usually with n-BuLi) and quenched with electrophiles leading to a variety of tertiary phosphine boranes (Table 2.13). 

Table 2.14 Diphosphine boranes 64 with an ethylene bridge by the menthol methodology.

Busacca and co-workers have prepared menthol-derived phosphinite boranes 101 and 102, by direct addition of anionic secondary phosphine borane 100 to carbodiimides, yielding the chiral phosphinite boranes under ambient temperature conditions (Scheme 25). These and other derivatives, prepared by hydrophosphination of carbodiimides, were used in the synthesis of enantiomerically enriched phosphaguanidines with potential use as ligands in asymmetric catalysis. 

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