P V Tertiary Diazaphospholidines

The high yields and the flawless stereoselectivity of this rearrangement prompted the preparation of several o-hydroxyaryl diazaphospholidine oxides. 

This class of compounds is interesting because of its bifunctional character, displaying both an acidic OH and a basic phosphoryl group. Table 3.7 lists the o-hydroxy diazaphospholidine oxides prepared via P-0 to P-C rearrangement. 

Unsubstituted and o/ -substituted substrates (entries 1-3) give the expected products in good yields. The reader will have noticed that examples in entries 5-9 were chosen to study the regioselectivity of the rearrangement. It was found to be excellent with the exception of 2-naphthalene substituted substrate (entry 9). In the other cases, electronic (entries 5 and 6) or steric factors (entry 7) govern at which position the carbanion is more likely to be formed. 

Compound 16 is formed in 89% yield starting from 12 with clean retention of configuration at the phosphorus atom as determined by X-ray diffraction. This compound is the product of two consecutive (first P-O to P-C followed by P-N to P-C) diastereoselective [1,3] rearrangements. The fact that 16 can also be prepared from 13 suggests that the P-N to P-C migration only occurs once the P-0 to P-C step has been completed. 

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