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A site adjacent to the unsaturated carbon atom is called the allylic position or allylic site. A group attached at this site is sometimes described as allylic. Thus, CH 2 =CHCH 2 OH "has an allylic hydroxyl group". Allylic C−H bonds are about 15% weaker than the C−H bonds in ordinary sp 3 carbon centers and are thus more reactive.
Allyl alcohol is converted mainly to glycidol, which is a chemical intermediate in the synthesis of glycerol, glycidyl ethers, esters, and amines. Also, a variety of polymerizable esters are prepared from allyl alcohol, e.g. diallyl phthalate. [5] Allyl alcohol has herbicidal activity and can be used as a weed eradicant [9]) and fungicide. [8]
An allylic rearrangement or allylic shift is an organic chemical reaction in which reaction at a center vicinal to a double bond causes the double bond to shift to an adjacent pair of atoms: It is encountered in both nucleophilic and electrophilic substitution , although it is usually suppressed relative to non-allylic substitution.
The Sharpless epoxidation is an example of an enantioselective process, in which an achiral allylic alcohol substrate is transformed into an optically active epoxyalcohol. In the case of chiral allylic alcohols, kinetic resolution results. Another example is Sharpless asymmetric dihydroxylation. In the example below the achiral alkene yields ...
If Y is sulfur, the product can be treated with a thiophil to generate an allylic alcohol in what is known as the Mislow–Evans rearrangement. A [2,3]-rearrangement may result in carbon-carbon bond formation. It can also be used as a ring-expansion reaction. [2]
One workaround to avoid this method is to reduce the carboxylic acid derivative all the way down to an alcohol, then oxidize the alcohol back to an aldehyde. Other alternatives include forming a thioester or a Weinreb amide, then reducing the new species to an aldehyde through the Fukuyama reduction or Weinreb reaction respectively, or using ...
Carbonyl allylation has been employed in the synthesis of polyketide natural products and other oxygenated molecules with a contiguous array of stereocenters. For example, allylstannanation of a threose-derived aldehyde affords the macrolide antascomicin B, which structurally resembles FK506 and rapamycin, and is a potent binder of FKBP12. [12]
The dipoles are categorized as allyl-type or propargyl/allenyl-type based on the geometry of the central atom. A 1,3-dipole is an organic molecule that can be represented as either an allyl-type or a propargyl/allenyl-type zwitterionic octet/sextet structures. Both types of 1,3-dipoles share four electrons in the π-system over three atoms.