The wittig rearrangement as a practical method for aldehyde synthesis

摘要: If the rearrangement of metalated allyl ethers, e.g., I, is accomplished in presence potassium tert-butoxide, primary alkyl groups preferentially migrate to unsubstituted allylic terminus (g-position). Enolates (Z)-R3CHR4CR1R2CH2CH:CHOLi and 1-vinylalcoholeates (Z)-CH2:CHCH(OLi)CR1R2CHR3R4 (by migration a-position, adjacent oxygen atom) are produced an approx. ratio 9:1. Because endo-configuration their organometallic precursors, enolates exclusively emerge (Z)-configuration as shown by trapping with chlorotrimethylsilane isolation resulting O-silyl (Z)-enethers. Hydrolysis latter affords corresponding aldehydes good yields. The mechanistically still obscure. A concerted process main reaction mode unlikely. intermediacy zwitterionic metallomers, II, solvent caged radical pairs, III, tentatively suggested. [on SciFinder (R)]