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36.12.9.1.3.2 Variation 2: Phosphate-Based Carbanion Rearrangements

DOI: 10.1055/sos-SD-036-00789

Morey, J. V.; Wheatley, A. E. H.Science of Synthesis, (2008361131.

It has been known for some years that phosphates bearing α-oxy carbanions can rearrange (see Scheme 32, Section 36.12.9.1.3),[‌61‌] and work by Hammerschmidt has recorded the deprotonation of dialkyl benzyl phosphates by chiral lithium amides.[‌62‌] Experimental data points to configurational stability of the short-lived benzylic carbanions, relative to 1,2-rearrangement to the metal alcoholate via carbanion attack on the internal electrophile (the phosphoryl unit). Deprotonation of homochiral diethyl (S)-phenyl[D1]methyl phosphate proceeds with a significant primary kinetic isotope effect, and isomerization yields an enantiomeric excess of up to 85%.[‌62‌] More recently, work on the treatment of alkyl diisopropyl phosphates with butyllithium/N,N,N,N-tetramethylethylenediamine has led to the transmetalation of stannane (±)-94 to give phosphonate (±)-96 via an acetic acid quench of alcoholate (±)-95 (Scheme 34).[‌63‌]

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Meeeeeeeeee 88

M8 Meeee (88/88) Meeee (%) ee 88 + 88 Mee
M 8:8 88 [‌88‌]
Me 8:8 88 [‌88‌]
(MM8)8Me 8.8:8 88 [‌88‌]
eMe 8:8.8 88 [‌88‌]
e-Me 8:88.8 88 [‌88‌]

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Meeeeeeeeee (8-Meeeeeeeeeee)eeeeeeeeeee (88); Meeeeee Meeeeeeee:[‌88‌]

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