Ketones reaction with acyl halides

Reactions with Acyl Halides. The palladium-carbon bond in alkyl VII and acyl VIII complexes also can be broken by acyl and alkyl halides, respectively, to give ketones (55). The reaction of the benzyl complex Vila with acetyl chloride in the presence of 2,6-lutidine provided good yield of methyl benzyl ketone, XVII. In the absence of the base, lower yields (26% ) were obtained. Surprisingly, a similar reaction between the benzyl complex and an excess of phenylacetyl chloride afforded a 156% yield of dibenzyl ketone, XVIII, based on the starting benzyl complex (see bottom of p. 105). 

Enamines may be regarded as synthetic equivalents of enolate ions and are closely related to the enolates derived from ketones in their reactions with acyl halides, alkyl halides and a,3-unsaturated compounds. 

A.iv. Reaction with Acid Chlorides. As briefly mentioned in Section 8.4.C.ii, the reaction of a dialkyl cuprate and an acid chloride is a preferred method to synthesize ketones.399,400 -phe reaction with acyl halides usually requires low temperatures to isolate the ketone product.388,387 -p is method is usually preferable to and more general than one that uses dialkylcadmium reagents (sec. 8.4.C.ii). Masamune et al. used this reaction to convert acid 422 to ketone 423 in a synthesis of erythronolide. In this case, oxalyl chloride was used to prepare the requisite acid chloride because of the sensitive nature of the molecule. 

Historically, the first report of the Pd-catalyzed cross-conpling reaction with acyl halide used organomercury compounds. " Although alkyl- and arylmercnry chlorides did not work, the use of dialkyl- and diarylmercury componnds gave the desired ketones in good yields. Acyl bromides are necessary to bring about fruitful results. The use of HMPA as the solvent is also unavoidable (Scheme 9). 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

The (V-methyldihydrodithiazine 125 has also been used as an effective formyl anion equivalent for reaction with alkyl halides, aldehydes, and ketones (77JOC393). In this case there is exclusive alkylation between the two sulfur atoms, and hydrolysis to give the aldehyde products is considerably easier than for dithianes. However, attempts to achieve a second alkylation at C2 were unsuccessful, thus ruling out the use of this system as an acyl anion equivalent for synthesis of ketones. Despite this limitation, the compound has found some use in synthesis (82TL4995). 

The reaction between acyl halides and diazomethane is of wide scope and is the best way to prepare diazo ketones. Diazomethane must be present in excess or the HX produced will react with the diazo ketone (10-74). This reaction is the first step of the Amdt-Eistert synthesis (18-8). Diazo ketones can also be prepared directly from a carboxylic acid and diazomethane or diazoethane in the presence of dicyclohexyl-carbodiimide. ... 

Procedures for the synthesis of ketones based on coupling of organostannanes with acyl halides have also been developed.211 The catalytic cycle is similar to that involved in coupling with aryl halides. The scope of compounds to which the reaction is applicable includes tetra-u-butylstannane. This example indicates that the reductive elimination step competes successfully with (3-elimination. 

Similar conditions are used to effect reactions of allylsilanes with acyl halides, resulting in (3,y-unsaturated ketones.128... 

Reactions with Acylium Ions. Alkenes react with acyl halides or acid anhydrides in the presence of a Lewis acid catalyst to give (3,y-unsaturated ketones. The reactions generally work better with cyclic than acyclic alkenes. 

Spawn and Burton investigated the reactions of the trifluorovinylzinc reagent with acyl halides. The reactions were sluggish and gave low yields of the trifluorovinyl ketones. Flowever, with Cu(I)Br catalysis, the acylation occurred rapidly and gave excellent yields of the trifluorovinyl ketones (equation 65)58. 

Reaction of halo ketones or diazo ketones with boranes 0-102 Carbonylation of alkyl halides 0-104 Reaction between acyl halides and organometallic compounds 0-105 Reaction between other acid derivatives and organometallic compounds... 

The acylation of unsaturated ketones constitutes one of the earliest routes to pyrylium salts (19CB1195). The reaction is better achieved with acyl halides than by anhydrides, and aliphatic are preferable to aromatic acid derivatives. The presence of a Lewis or Bronsted acid is usually necessary and iron(III) chloride, aluminum chloride, boron trifluoride and perchloric acid have found frequent application. It is considered that these interact with the acid derivative to generate the actual acylating agent. 

Aryl ketones can also be prepared by C-acylation of support-bound arylstannanes with acyl halides (Entry 4, Table 12.1). The reaction conditions are mild and suitable for selective chemical transformations of polystyrene-bound intermediates. As an alternative, resin-bound arylstannanes can be converted into benzophenones by treatment with aryl halides and carbon monoxide ([(Pd(PPh3)4], DMSO, 80 °C, 18 h-3 d [8]). 

The acylpalladium is formed by CO insertion as the intermediate of the carbonylation. They can be prepared directly by the oxidative addition of acyl chlorides to Pd(0). Thus ketones can be prepared by the reaction of acyl halides with organozinc reagents and organostannanes. Benzoacetate (490) is obtained by the reaction of benzoyl chloride with the Reformatsky reagent 489 [243], The macrocyclic keto lactone 492 is obtained by intramolecular reaction of the alkenylstannane with acyl chloride in 491 [244]. 

One of the best known reactions of dialkyl cadmium compounds is that with acyl halides which results in the formation of ketones. The reactions of (CF3)2Cd glyme with CH, COBr and C6HhCOC1 were the third class of reactions of the trifluoromethylating reagent examined. However, the mixed trifluoromethylalkyl or -aryl ketones were not observed. The organic products obtained were the acyl fluorides (95% yield) along with difluorocarbene. The latter could be stereospecifically trapped at temperatures as low as -78°C. The addition of either lithium or magnesium halides to the reaction mixture did not affect the outcome (106). 

The reaction is often followed by protonation of the oxygen. The C=0 group may be present in an aldehyde, ketone, ester, anhydride, acyl halide, amide, and so forth. Acid catalysts may be necessary with weak nucleophiles. The acid protonates the oxygen, making the carbon more positive and thus, more electrophilic. 

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