Allylation ketones

Aryl aldehydes, alkane reduction, 71-72 Aryldiazonium salts, reduction of, 104 Aryl halides and triflates, reduction reaction, 32 Aryl ketone, allylation,... 

Carbanions, generated by the reaction of benzylsilanes with tetra-n-butylammo-nium fluoride react with non-enolizable aldehydes to produce the alcohol [67], When a stoichiometric amount of the ammonium fluoride is used, the methylarene corresponding to the benzylsilane is frequently a by-product and arises from formation of the hydrogen difluoride salt during the reaction. When only catalytic amounts of the ammonium fluoride initiate the reaction, the formation of the methylarene is suppressed. In a similar type of reaction (although the mechanism is not known) between aldehydes and ketones, allyl bromide, and tin in the presence of trimethylsilyl chloride the yield of the but-l-en-4-ol is raised significantly by the addition of tetra-n-butylammonium bromide, particularly in the reactions with... 

Unlike aldehydes and ketones, allylic boron compounds are not ubiquitous, commercial organic substrates. There are several methods for the preparation of allylic boronates, however, and many of these have been developed in the past decade. This topic has been reviewed recently " so only the most common methods are emphasized in this section. As a result of the lesser stability of allylic boranes, methods to access these reagents are more limited and it is generally easier to prepare allylic boronates with a wide range of functional groups. 

In addition, the use of enzyme selective inhibitors has turned out to be very effective. Reductions were performed by adding l,l,l-trifluoro-2,4-pentane-dione 1 to a yeast-water suspension with selected additives such as methylvinyl-ketone, allyl alcohol, alkanoic acids, ethyl chloroacetate or allyl bromide, all of them reported to affect the stereochemical course of baker s yeast reduction. In some cases, both the influence of the yeast/substrate ratio and the influence of the presence of glucose were considered. In the presence of alkanoic acids (acetic, fumaric, or oleic acid), no significant effect was observed. However, addition of methylvinyl-ketone, allyl alcohol, ethyl chloroacetate and allyl bromide to the reaction system affected the stereochemical course of the reduction of 1. In particular, (R)-(+)-2 was produced in the presence of ethyl chloroacetate and allyl bromide as additive. 

Ketones were also reacted under these conditions, leading to tertiary ethers. Thus, by mixing equimolar quantities of a carbonyl (aldehyde or ketone), allyl-silane and a silylated alcohol, followed by the addition of a catalytic amount of TMSOTf, homoallylic ethers can be obtain in good yields via a three-component coupling reaction (Scheme 13.22). 

Asymmetric catalysis undertook a quantum leap with the discovery of ruthenium and rhodium catalysts based on the atropisomeric bisphosphine, BINAP (3a). These catalysts have displayed remarkable versatility and enantioselectivity in the asymmetric reduction and isomerization of a,P- and y-keto esters functionalized ketones allylic alcohols and amines oc,P-unsaturated carboxylic acids and enamides. Asymmetric transformation with these catalysts has been extensively studied and reviewed.81315 3536 The key feature of BINAP is the rigidity of the ligand during coordination on a transition metal center, which is critical during enantiofacial selection of the substrate by the catalyst. Several industrial processes currently use these technologies, whereas a number of other opportunities show potential for scale up. 

This ligand, MeO-BIPHEP (96a), has shown similar reactivities and enantioselectivities to catalysts that contain BINAP.117 Ruthenium catalysts that contain MeO-BIPHEP have been used in several asymmetric hydrogenations from bench scale to multi-ton scale, which include the large-scale preparation of a P-keto ester, an aryl ketone, allylic alcohol, and several oc,P-unsaturated carboxylic acid substrates, which are shown in Figure 12.5. 

In addition to the above-mentioned monomers, various acrylic and methacrylic esters, methacrylonitrile, itaconic acid, crotonic acid, methyl vinyl ketone, allyl alcohol, allyl amine etc., have been studied by Fischer... 

Anions formed from group 6 and manganese Fischer carbene complexes undergo aldol condensations with aldehydes and ketones. Allylic carbenes exclusively react in the y position with aldehydes affording dienyl-substituted carbenes. For alkoxy-substituted carbenes, the presence of an excess Lewis acid see Lewis Acids Bases), such as boron trifluoride etherate, titanium tetrachloride, or tin tetrachloride is required for the reaction to proceed in reasonable yield. The initial aldol product can be isolated without elimination (Scheme 12). ... 

Hydroxy-4-phenyl-VI/la,2. 1483 (Keton + Allyl-M) Vl/lb, 540f. (Isomerisier.) E19a, 392 (En-Oxigenier.)... 

Lead acetate azides, Pb(OAc)4 (N3)n, prepared in situ from lead tetraacetate and azidotrimethylsilane, react with alkenes to yield a variety of products, depending on the structure of the alkene 1,2-diazides. 1,2-acetoxy azides, a-azido ketones, allylic azides, and <5-oxo nitriles (by the oxidative cleavage of cyclohexene rings)97. The diazides and acetoxy azides are formed by preferential syn addition, but the diastereoselectivity (up to 3 1) is far from satisfactory with both acyclic and cyclic alkenes98,99. 

Allyltin compounds readily add to aldehydes and ketones. Allylic bromides react with tin to generate the organometallic in situ, which then adds to aldehydes. Allylic chlorides react with aldehydes in the presence of ditin compounds such as MesSn—SnMes and a palladium catalyst. Allyltrialkyltin compounds ... 

TBA5PMW11O39, where M = Co, Mn, Cu, Ni, or Fe Alkenes Epoxide, allylic ketone, allylic alcohol o2 MeCN and aldehyde Aldehyde reductant quite selective 303 K 402... 

TBA4H6(Fe2- Ni(0Ac)3)PW9037 Alkane Alkene Aldehyde Alcohol, ketone Allylic alcohol, allylic ketone, epoxide Carboxylic acids 02 or h2o2 o2 o2 MeCN 82 °C or 50 °C 30 °C 30 °C 403... 

THA4(Cr0)PWu039 THA,5(Cr0)SiW11039 Alkene Alkene Allylic alcohol Triphenylphosphine Epoxide, allylic alcohol, allylic ketone Epoxide, allylic alcohol, allylic ketone Allylic ketone Triphenylphosphine oxide MeCN or C6H6 MeCN or C6H6 MeCN c6h6 ... 

In the case of the observation of poor overall enantioselectivity due to the presence of two competing enzymes with different enantioselectivities, one of the most straightforward methods to improve the enantioselectivity is the use of the inhibitor of the unnecessary enzyme(s). Ethyl chloroacetate, methyl vinyl ketone, allyl alcohol, allyl bromide, sulfur compounds, Mg2+, Ca2+, etc. have been reported as inhibitors of enzymes in yeast [87 97l... 

The conjugated thionium ylids are prepared by the Pummerer reaction of an allyl sulphoxide, with trimethylsilyl triflate in the presence of ethyl diisopropylamine, and give products of ketone allylation [equation (52)... 

Reduction of aldehydes and ketones allylic alcohols from a, 3-unsaturated aldehydes and ketones alcohols from carboxylic acid chlorides amines from aliphatic azides.21 ... 

TiCl4 immobilized on surface of PE modified by graft polymerization of vinylpyridine, acrylonitrile, methyl vinyl ketone, allyl alcohol, allylamine, allyl sulfide or acrylic acid, has been studied with IR spectroscopy and XPS I166J. Cluster aggregates of Ti(IV) fixed on the surface, were discovered. Their formation did not cause the reduction of Ti(IV). In binary catalytic systems of Ti(IV) on an organo-aluminum polymeric support, Ti(IV) was reduced to Ti(III), and Ti(II) appeared at 343 K. The high and stable activity of immobilized titanium compounds during ethylene polymerization was attributed to deceleration of Ti(IV) reduction processes. 

The magnesium-mediated reductive trifluoromethylation also works for other structurally diverse chlorosilanes. Chlorotriethyl-silane, f-hutyldimethylsilyl chloride, and tris(trimethylsilyl)silyl chloride have been applied to prepare corresponding trifluoro-methyl-containing silanes. However, the reductive trifluoromethylation did not take place with other electrophiles such as aldehydes, ketones, allyl bromide, benzyl chloride, or tributyltin chloride. Even tributyltin hydride and allyltrimethylsilane showed no reactivity The reason for such behavior is not clear. Probably, chlorosilanes play an important role during the reductive trifluoromethylation both as a silylating agent and a single-electron transfer promoter. 

Keywords Ketones, allyl bromide, Zn-Cu couple, solvent-free, room temperature, allylation,... 

CO) aromatic O, quinones, lactones, lactams, unsaturated cyclic ketones, allyl aldehydes... 

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