Secondary phosphine boranes resolution

A limitation of the method is that all the phosphine boranes of Table 2.6 bear the -P(BH3)(f-Bu)Ph group. The dynamie resolution procedure could become much more versatile method if it could be applied to wide variety of secondary phosphine boranes. Surprisingly, this subject has been scarcely studied and only a few other aryldialkylphosphine boranes have been prepared (Scheme 2.7 and Table 2.7). 

Examples of electrophilic addition of secondary phosphines to alkenes or alkynes were described. [114, 124, 125, 135]. Glueck [124-126] reported enantioselective tandem reaction of alkylated/arylation of primary phosphines catalyzed by platinum complex, proceeding with formation of chiral phosphaace-naphthenes. Palladium-catalyzed hydrophosphination of alkynes 219 tmder kinetic resolution conditions gave access to 1,1-disubstituted vinylphosphine boranes 220. However, despite screening several chiral ligands, temperatures, and solvents, the... 

In the early studies, the phosphine oxides resolved contained substituents with aromatic condensed rings (entries 2 and 3) but later other oxides without that substitution were also resolved (entries 1 and 5) and even secondary phosphine oxides (entry 7). Entries 8-15 show some resolutions of the phosphine boranes including examples with several stereogenic centres in the backbone (entries 11-14). Compound of entry 11 can be regarded as a hybrid between BPE and DiPAMP. A few diastereomeric pairs have also been resolved by HPLC (entries 16 and 17), because conventional methods such as column chromatography or recrystallisation failed. 

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