THE WITTIG REARRANGEMENT AS A PRACTICAL METHOD FOR ALDEHYDE SYNTHESIS
If the rearrangement of metalated allyl ethers 2 (or 4) is accomplished in the presence of potassium tert-butoxide, primary alkyl groups preferentially migrate to the unsubstituted allylic terminus (γ-position).Enolates 7 and 1-vinylalcoholates 6 (by alkyl migration to the α-position, adjacent to the oxygen atom) are produced in an approximate ratio of 9 : 1.Because of the endo-configuration of their organometallic precursors, the enolates exclusively emerge in the (Z)-configuration as shown by trapping with chlorotrimethylsilane and isolation of the resulting O-silyl (Z)-enethers.Hydrolysis of the latter affords the corresponding aldehydes with good yields. -The rearrangement is mechanistically still obscure.A concerted process as the main reaction mode is unlikely.The intermediacy of zwitterionic metallomers 18 and solvent caged radical pairs 17 is tentatively suggested.
Schlosser, Manfred,Strunk, Sven
p. 2649 - 2664
(2007/10/02)
More Articles about upstream products of 124471-56-3