Alkenes => aldehydes

For the oxidation of allylic alcohols to alkene aldehydes, also see Section 48 (Aldehydes from Alcohols). 

As in the P(III) chemistry above, both late metal (Pd) and lanthanide catalysts have been used for P(V)-H additions to alkynes, alkenes, aldehydes, and imines. In addition, titanium, aluminum, and zinc catalysts have been employed. Typical P(V) substrates include dialkyl phosphites P(0R)2(0)H and phosphine oxides PR2(0)H. 

A variety of double bonds give reactions corresponding to the pattern of the ene reaction. Those that have been studied from a mechanistic and synthetic perspective include alkenes, aldehydes and ketones, imines and iminium ions, triazoline-2,5-diones, nitroso compounds, and singlet oxygen, 10=0. After a mechanistic overview of the reaction, we concentrate on the carbon-carbon bond-forming reactions. The important and well-studied reaction with 10=0 is discussed in Section 12.3.2. 

A reaction related to alkene-aldehyde coupling is the alkene-imine coupling. A one-pot cyclization involving such a reaction (Eq. 3.27) proceeds smoothly in a mixture of water-THF. The reaction has been used in the asymmetric synthesis of pipecolic acid derivatives.114... 

Alcohols can be made from monohaloalkanes, alkenes, aldehydes and ketones. 

Free radical hydrosilylation of poly(phenylsilanes) (294) with alkenes, aldehydes or ketones promoted by 2,2 -azo(bisisobutyronitrile) (AIBN) provides functional polysilanes (295) possessing a variety of properties (equation 111)292. 

Hexanol (alkane alcohol) ( )-2-Hexenal (alkene aldehyde) Methyl anthranilate (= Methyl 2-aminobenzoate) (aryl ester)... 

To establish the relative configuration of the newly formed stereocenters of the bridged 1,2-oxazocine 109, obtained from an alkene-aldehyde intermediate, a computer-assisted molecular modeling coupled with I/hh calculations was utilized. 

Similar to the benzynezirconocene, cyclohexyne, cyclopen-tyne, alkyne, alkene, cycloaUcene zirconocenes, and related species insert various substrates such as alkynes, alkenes, aldehydes, ketones, nitriles or phosphaalkynes. They lead in general five-membered zirconacycles, which can be converted by transmetalation or exchange reactions into fused-ring aromatic or heterocyclic compounds. The extension of this chemistry to heterobenzyne complexes can be realized, for instance, in phosphinine compounds. Consequently, under mild conditions, ) -phosphabenzyne-zirconocene complexes are formed and can be isolated either as PMes adducts or as dimers when the elimination reaction is carried out without added phosphane (Scheme 28). 

Coverage in this chapter is restricted to the use of alkenes or alkynes as enophiles (equation 1 X = Y = C) and to the use of ene components in which a hydrogen is transferred. Coverage in Sections 1.2 and 1.3 is restricted to ene components in which all three heavy atoms are carbon (equation 1 Z = C). Thermal intramolecular ene reactions of enols (equation 1 Z = O) with unactivated alkenes are presented in Section 1.4. Metallo-ene reactions are covered in the following chapter. Use of carbonyl compounds as enophiles, which can be considered as a subset of the Prins reaction, is covered in depth in Volume 2, Chtqiter 2.1. Addition of enophiles to vinylsilanes and allylsilanes is covered in Volume 2, Chapter 2.2, while addition of enophiles to enol ethers is covered in Volume 2, Chapters 2.3-2.S. Addition of imines and iminium compounds to alkenes is presented in Volume 2, Part 4. Use of alkenes, aldehydes and acetals as initiators for polyene cyclizations is covered in Volume 3, Chapter 1.9. Coverage of singlet oxygen, azo, nitroso, S=N, S=0, Se=N or Se=0 enophiles are excluded since these reactions do not result in the formation of a carbon-carbon bond. 

It is possible to treat ketones with allyl alcohol and an acid catalyst to give y,8-unsaturated ketones directly, presumably by initial formation of the vinylic ethers, and then Claisen rearrangement. In an analogous procedure, the enolates (134) of allylic esters [formed by treatment of the esters with lithium isopropylcyclohexyla-mide (LICA)] rearrange to y,5-unsaturated acids. Allylic alcohols can be treated with a catalytic amount of mercuric acetate, and in the presence of an excess of allyl vinyl ethers give an alkene-aldehyde via a Claisen rearrangement. 

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