Ketones tetrakis palladium

The scope of the Negishi-coupling is not limited to aryl and vinyl halides and sometimes acyl chlorides might also be converted to ketones by this protocol. The 2,3-dihalopyrrole derivative shown in 6.22. was converted into its 2-lithio derivative by selective lithium-halogen exchange at -78 °C. Addition of zinc chloride effected the formation of the appropriate pyrrolylzinc chloride, which was coupled with a functionalised butyroyl chloride in the presence of tetrakis(triphenylphosphino)palladium and furnished the expected 2-acylpyrrole in 61% yield.27... 

Stereoselective allylic alkylations have been carried out with the aid of palladium catalysts. The 17-(Z)-ethylidene groups of steroids (obtained from the ketones by Wittig olefination) form n-allyl palladium complexes in the presence of copper(n) salts (B.M. Trost, 1974, 1976). Their alkylation with dimethyl malonate anions in the presence of 1,2-ethane-diylbis[diphenylphosphine] (— diphos) gives a reaction exclusively at the side chain and only the (20S) products. If one starts with the endocyclic 16,17 double bond and replaces an (S)-20-acetoxy group by using tetrakis(triphenylphospbine)palladium,the substitution occurs with complete retention of configuration, resulting from two complete inversions (B.M. Trost, 1976). 

Conjugate reduction of a,/l-enals and -enones. Tri-n-butyltin hydride in the presence of tetrakis(triphenylphosphine)palladium effects conjugate reduction of a, /J-unsaturated aldehydes and ketones in the presence of a proton source (water, acetic acid). Yields are improved by addition of a radical scavenger.15 Double bonds bearing... 

UNSATURATED KETONES Pytidinium chlorochromate. Tetrakis-(tripheny Iphosphine) palladium 0). 

When 3,3-dimethylcyclopropene is exposed to carbon monoxide under pressure in the presence of tetrakis(triphenylphosphane)palladium as catalyst, 3,3,6,6,10,10-hexamethyl-exo,enrfo-tet-racyclo[7.1.0.0 " .0 ]decan-8-one (hexamethyl-tris-cr-homotropone, 10) is formed as the main product (72.2%) along with carbonyl-free di- and oligomerization products. At ambient pressure with an in situ generated palladium(O) catalyst, only a 20% yield of the tetracyclic ketone 10 is obtained. 

Oxatrimethylenemethanepalladium complexes can also be generated by oxidative addition of palladium(O) to 5-methylene-l,3-dioxolan-2-ones and subsequent decarboxylation. Again, reaction with norbornene, norbornadiene and dicyclopentadiene yields polycyclic cyclopropyl ketones in medium to high yield (Table 19). In this case, tetrakis(triphenylphosphane)pal-ladium(O) was the best catalyst found, whereas tris(dibenzylideneacetone)palladium(0)-chloro-form/triphenylphosphane (see above) and bis(cycloocta-l,5-diene)nickel/triphenylphosphane (used in stoichiometric amounts) proved less efficient. 

Enol ethers of alkyl cyclopropyl ketones are alkylated or carboxylated under the correct conditions. Methyl ann, c ,cw-2,9,9-trimethyl-5-trifluoromethylsulfonyloxytricyclo[5.3.0.0 " ]dec-5-ene-4-carboxylate on treatment with palladium(II) acetate in methanol containing triethylamine under a carbon monoxide atmosphere resulted in diester formation giving dimethyl fln ,c .5,cw-2,9,9-trimethyltricyclo[5.3.0.0 ]dec-5-ene-4,5-dicarboxylate in excellent yield (93%). The same substrate was converted to methyl anr/,cw,d. -5-formyl-2,9,9-trimethyltricyclo[5.3.0.0 ]dec-5-ene-4-carboxylate in 88% yield on carbonylation in the presence of tetrakis(triphenylphosphane)palladium, tributyltin hydride, and lithium chloride. ... 

KETONES f-Butyl a-lithioisobutyrate. Benzoin. Chlorocarbonylbis(triphenylphosphine)-rhodium(I). m-Chloroperbenzoic acid. Chromic acid. Dimethylcopperlithium. Diphenyl disulfide. Formaldehyde diphenyl thioacetal. Methylthioacetic acid. Sodium cyanide. Tetrakis triphenylphosphine)palladium(0). Trimethylchlorosilane. Triphenyl-methyl isocyanide. Trimethylsilyl cyanide. 

Esters 106 (R = Me, Et or Pr = Et, Pr, r-Bu or PhCHi) of aliphatic carboxylic acids react with lithium acetylides 107 (R = H, C5 Hi i or Ph) in the presence of boron trifluoride etherate in THE to give acetylenic ketones 108 (equation 18). Palladium-[tetrakis(triphenylphosphine)]-copper(I) iodide catalyses the oxidative addition-decarboxylation of propargyl methyl carbonates, e.g. 109, with terminal alkynes to yield 1,2-dien-4-ynes (allenylacetylenes) 110. The regiochemistry of the palladium-catalyzed addition of phenylacetylene to the allenic ester 111 depends on the nature of the catalyst used palladium(III) acetate-triphenylphosphine yields a 81 19 mixture of adducts 112 and 113, while in the presence of tetrakis(carbomethoxy)palladacyclopentadiene-tris(2,4,6-trimethoxyphenyl)phosphine the ratio is reversed to 9 91 k... 

Enantiomerically pure epoxide 307 was synthesized in 16 steps from D-(-)-quinic acid, an inexpensive plant metabolite. Intramolecular cyclization was observed with a catalytic amount of tetrakis(triphenylphosphine)palladium(0) at 25 °C to afford the optically active isoquinuclidine in 95% yield. The introduction of alkyl groups, such as the ethyl group of ibogamine and catharanthine, can easily be accompUshed at the epoxy ketone stage. 

A variety of a-nitroepoxides undergo conversion to the corresponding 1,2-diketones or, in some cases, a-nitroketones with tetrakis(triphenylphosphine)palladium(0) (Scheme [io],[ii] Proposed reaction mechanism is shown in Scheme 16. 2,3-Epoxy alcohols also undergo the Pd(0)-catalyzed reaction to be isomerized to a- or /3-hydroxy ketones or both, depending on the nature of the substituents on the phenyl ring (Scheme... 

Enol phosphates derived from thiol esters couple with organoaluminium reagents, catalysed by tetrakis(triphenylphosphine) palladium, to form enol thioethers, and hence ketones by hydrolysis [equation (22)]. This alkylative... 

TMS-alkynes are oxidized at the terminal carbon to carboxylic acids by hydroboration/oxidation (dicyclohexylborane/NaOH, H2O2). This does not work with TIPS-alkynes. Instead, TIPS-alkynes are cleanly monohydroborated at the internal carbon by 9-borabicyclo[3.3.1]nonane dimer to give (Z)- -borylvinyl-silanes. These can be oxidized in high yields to a-silyl ketones, or cross coupled with a bromide R Br (R = aryl, benzyl, dimethyl-vinyl) in the presence of NaOH and tetrakis(triphenylphos-phine)palladium(0) to give /3,/3-disubstituted vinylsilanes (Suzuki reaction eq 14). The same nucleophilic substituted vinylsilane can be added to an aromatic aldehyde to provide access to ( )-3-silyl allyl alcohols. ... 

Efficient and highly stereoselective alkylations of enol phosphates are accomplished with trialkylalanes in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium if alkenyl- or alkynyl-dialkylalanes are used, the unsaturated group is transferred specifically. Since enol phosphates are readily prepared from ketones, this constitutes a useful method for the transformation of ketones into alkyl-substituted olefins, 1,3-dienes, or 1,3-enynes e.g. Scheme 27). ... 

In a novel carbon-carbon bond-forming reaction, catalysed by tetrakis(triphenylphosphine)palladium, allyl /8-keto-carboxylates are efficiently decarboxylated at room temperature to give y,5-olefinic ketones, alkylation taking place regioselectively at the carbon which originally bore the carboalkoxy-group e.g. Scheme 70). Diallylated by-products are observed in some cases. 

The role of palladium in organic synthesis continues to be explored and exploited. Enol stannanes are monoalkylated by allylic acetates in the presence of tetrakis(triphenylphosphine)palladium, Enol stannanes give higher selectivity for monoalkylation than enolate ions or silyl enol ethers. High regioselec-tivity is observed for alkylation at the less substituted end of the allyl moiety. Olefins, after complexation to palladium(ll), alkylate enolate anions. The organopalladium product may be converted into saturated ketones, or into enones by /3-elimination, or acylated with carbon monoxide (Scheme... 

Tetrakis(triphenylphosphine) palladium oxygen Ketones from oximes under mild conditions... 

A soln. of dibenzyl ketoxime in benzene added at room temp, to a soln. of peroxobis(triphenylphosphine)palladium prepared by bubbling O2 for 0.5 hr. into a soln. of tetrakis(triphenylphosphine)palladium in benzene, and the product isolated after 5 min. dibenzyl ketone. Y 98%. - This method is recommended for unsatd. and acid- or base-sensitive compds. F. e. and limitations s. K. Maeda et al., Tetrah. Let. 1974, 797. 

A hydroxyl group may be introduced a- to a ketone group by the reaction of chromyl chloride with the ketone silyl enol ether in dichloromethane at low temperature, No a-chloro-ketones were observed as by-products. Alternatively, an alkoxy-group may be introduced by the reaction of the silyl enol ether with alkyl hypochlorites, catalysed by tetrakis(triphenylphosphine)palladium. ... 

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