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The Wittig reaction involves reaction of an aldehyde or ketone with a Wittig reagent (or phosphorane) of the type Ph 3 P=CHR to produce an alkene and Ph 3 P=O. The Wittig reagent is itself prepared easily from triphenylphosphine and an alkyl halide.
The alkene donates electron density into a π-acid metal d-orbital from a π-symmetry bonding orbital between the carbon atoms. The metal donates electrons back from a (different) filled d-orbital into the empty π * antibonding orbital. Both of these effects tend to reduce the carbon-carbon bond order, leading to an elongated C−C distance ...
The radicals formed from alkenyl peroxides can be utilized in organic radical reactions. For example, they can mediate hydrogen atom abstraction reactions and thus lead to the functionalization of C-H bonds, [7] or they can be used to introduce ketone residues by addition of the alkenyloxyl radicals to alkenes. [8] [9] [10]
The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction. The type of addition that occurs depends on multiple different factors of a reaction, and is defined by the final orientation of the substituents on the parent molecule.
The reverse reaction, the de-insertion of CO and alkenes, are of fundamental significance in many catalytic cycles as well. Widely employed applications of migratory insertion of carbonyl groups are hydroformylation and the carbonylative production of acetic acid. The former converts alkenes, hydrogen, and carbon monoxide into aldehydes.
In organic chemistry, alpha-elimination refers to reactions of this type: [1] R 2 CHX → R 2 C: + HX. The reaction is employed to generate carbenes and nitrenes. The formation of dichlorocarbene from chloroform is an example. Alpha eliminations contrasts with beta eliminations, which are commonly used to generate alkenes: R 2 CHCXR' 2 → R 2 ...
Diastereoselective epoxidation may be achieved through the use of alkene starting materials with diastereotopic faces. When racemic 3-isopropylcyclohexene was subjected to DMD oxidation, the trans epoxide, which resulted from attack on the less hindered face of the double bond, was the major product.
Dihydroxylation is the process by which an alkene is converted into a vicinal diol.Although there are many routes to accomplish this oxidation, the most common and direct processes use a high-oxidation-state transition metal (typically osmium or manganese).