Stereoselective alkylations and rearrangements of chiral phosphonic and phosphinic acid derivatives

The stereochemical course of carbon migration from phosphorus to nitrogen and oxygen were investigated. Optically active ($\geq$99.9% e.e.) phosphonic and phosphinic azides were prepared and photolyzed in methanol to effect the phosphorus analogues of the carbonyl-Curtius rearrangement. These studies showed that carbon migration in the phosphinoyl-Curtius rearrangement proceeds with 99% net retention of configuration while the migration in the first example of the phosphonoyl-Curtius rearrangement occurs with 99.4% net retention of configuration.The stereoselectivity in the alkylation reactions of various chiral phosphorus-stabilized benzylic carbanions was also examined. Both racemic and scalemic 2-benzyl-1,3,2-oxazaphosphorinane-2-oxides were employed. The effects of solvent, base, additive, and electrophile were studied. The diastereoselectivity of alkylation is dependent on the phosphorus-stabilized carbanion which is used, but high diastereoselectivity (98:2-95:5) was realized.Multinuclear NMR spectroscopy was used to gain insight into the solution state structure of both symmetrical and unsymmetrical heterocyclic phosphorus-stabilized benzylic carbanions. The spectral data is consistent with a charge-alternating structure that has a planar anionic carbon. Information about the conformation of the anion as well as the ring form was obtained. Much information about the structure of phosphorus-stabilized carbanions was obtained through X-ray crystallographic studies of the first lithiated phosphonoyl-stabilized carbanion.U of I OnlyETDs are only available to UIUC Users without author permissio