Unsaturated carbonyl compounds trifluoroacetate

Woerpel and Calad tested for the formation of the silacarbonyl ylide by interrogating the behavior of the electrophilic silver silylenoid intermediate 115 toward a,(3-unsaturated carbonyl compounds (Scheme 7.37).82 They hypothesized that formation of silacarbonyl ylide 131 might trigger a 6jt-electrocyclization to form oxasilacyclopentene 132. As anticipated, exposure of cyclohexene silacyclopropane 58 to substoichiometric amounts of silver trifluoroacetate in the presence of a,(3-unsaturated carbonyl compounds 130 produced oxasilacyclopentenes 132. The reaction tolerated a substitution at the a and/or (3 position and was general for both esters and ketones. 

Palladium catalysts are best known for oxidizing alkenes to ketones or vinyl derivatives. However, formation of a, unsaturated carbonyl compounds by UV irradiation of oxygenated solutions of alkoies in the presence of catalytic amounts of palladium s ts has been observed by Muzait - This reaction is believed to proceed through a ir-allylpalladium trifluoroacetate complex, e.g. (77). 

Overall yield of a,0-unsaturated carbonyl compound. "Hydrolytic workup with aqueous acid. Anhydrous isomerization with trifluoroacetic acid followed by hydrolytic work-up with aqueous acid. 

Nucleophilic addition of Ti(IV)-enolates of diazo ketone (136) to cycloheptanone (186) affords alcohol 187 which, on further dehydration with trifluoroacetic anhydride gives a,P-unsaturated carbonyl compounds (188 189) in 58% yield.84... 

Aza-Cope rearrangement.7 This reaction proceeds readily when catalyzed by Pd(0) and a strong protic acid, particularly trifluoroacetic acid or methanesul-fonic acid. This isomerization is involved in a direct synthesis of S,e-unsaturated imines from allylamines with carbonyl compounds (equation I). The unsaturated... 

Allylic Oxidation. The Wacker reaction and related palladium-catalyzed oxidations which proceed via nucleophilic attack on coordinated alkene have been widely practiced in industry to produce acetaldehyde, acetone, and vinyl acetate. An alternative pathway is available to alkenes in the coordination sphere of palladium(ll) complexes, which could lead to another important family of oxidation products. Insertion into the allylic C-H bond of 1-alkenes gives TT-allyl complexes which, on attack by external nucleophiles, would produce a family of allylic oxidation products including a,fi-unsaturated alcohols, carbonyl compounds, and carboxylic acids. Electron- withdrawing anionic ligands such as trifluoroacetate enhance the ability of the palladium center to insert into C-H bonds in this manner [26] (Fig. lA). Catalytic conversion of propylene to allyl acetate has been achieved in high selectivity in the presence of catalytic quantities of palladium(ll) trifluoroacetate [27]. 

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