The Wittig rearrangement as a practical method for aldehyde synthesis
If the rearrangement of metalated allyl ethers, e.g., I, is accomplished in the presence of potassium tert-butoxide, primary alkyl groups preferentially migrate to the unsubstituted allylic terminus (g-position). Enolates (Z)-R3CHR4CR1R2CH2CH:CHOLi and 1-vinylalcoholeates (Z)-CH2:CHCH(OLi)CR1R2CHR3R4 (by alkyl migration to the a-position, adjacent to the oxygen atom) are produced in an approx. 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, e.g., II, and solvent caged radical pairs, e.g., III, is tentatively suggested. [on SciFinder (R)]
1989
45
9
2649
64
CAN 112:35255
23-14
Aliphatic Compounds
Inst. Chim. Org.,Univ. Lausanne,Lausanne,Switz.
Journal
written in English.
74-88-4 (Methyl iodide); 75-30-9 (Isopropyl iodide) Role: RCT (Reactant), RACT (Reactant or reagent) (alkylation by, of metalated allyl ethers); 42072-39-9 Role: RCT (Reactant), RACT (Reactant or reagent) (bromination of); 3739-64-8 (Allyl butyl ether) Role: RCT (Reactant), RACT (Reactant or reagent) (metalation and rearrangement of); 22299-70-3P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. and Grignard reaction of, with allyl chloromethyl ether); 37179-47-8P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. and conversion of, to methylhexadecenol); 124471-70-1P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. and conversion of, to methyloctanal); 592-72-3P; 1471-04-1P; 18022-46-3P; 82473-55-0P; 124471-48-3P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. and metalation and rearrangement of); 124471-49-4P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. and sequential lithiation and silylation of); 22509-78-0P; 31642-15-6P; 31642-16-7P; 33746-78-0P; 50300-19-1P; 51018-58-7P; 53379-16-1P; 53379-20-7P; 53379-23-0P; 53379-27-4P; 66007-18-9P; 76966-14-8P; 90270-49-8P; 124471-46-1P; 124471-47-2P; 124471-50-7P; 124471-51-8P; 124471-52-9P; 124471-53-0P; 124471-54-1P; 124471-55-2P; 124471-56-3P; 124471-57-4P; 124471-58-5P; 124471-59-6P; 124471-60-9P; 124471-61-0P; 124471-62-1P; 124471-63-2P; 124471-64-3P; 124471-65-4P; 124471-66-5P; 124471-67-6P; 124471-68-7P; 124471-69-8P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of); 123-51-3; 143-08-8 (1-Nonanol); 584-02-1 (3-Pentanol); 2516-33-8 (Cyclopropyl methanol) Role: RCT (Reactant), RACT (Reactant or reagent) (reaction of, with allyl bromide under phase transfer conditions); 107-18-6 (Allyl alcohol) Role: RCT (Reactant), RACT (Reactant or reagent) (reaction of, with chlorotriethylsilane in presence of triethylamine); 112-54-9 (Lauraldehyde); 123-38-6 (Propanal); 5903-39-9 (1,6-Heptadien-3-ol); 17206-61-0 (6-Heptenal) Role: RCT (Reactant), RACT (Reactant or reagent) (reaction of, with chlorotrimethylsilane in presence of triethylamine); 85160-80-1 Role: RCT (Reactant), RACT (Reactant or reagent) (reaction of, with methyloctanal); 3970-20-5 (Allyl chloromethyl ether) Role: RCT (Reactant), RACT (Reactant or reagent) (reaction of, with methylpentylmagnesium bromide); 106-95-6 (Allyl bromide) Role: RCT (Reactant), RACT (Reactant or reagent) (reactions of, under phase transfer conditions); 1746-13-0; 2290-45-1 Role: RCT (Reactant), RACT (Reactant or reagent) (sequential metalation and alkylation of); 22463-27-0 Role: RCT (Reactant), RACT (Reactant or reagent) (sequential reaction of, with potassium hydride and allyl bromide); 4048-42-4 (1-Dodecen-3-ol); 4938-52-7 (1-Hepten-3-ol) Role: RCT (Reactant), RACT (Reactant or reagent) (trimethylsilylation of)
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