Darzens-Nenitzescu reaction

Friedel-Crafts acylation of alkenes (Darzens-Nenitzescu reaction ) with unsaturated acylium ions generated from acid halides and Lewis acids constitutes a general synthesis of divinyl ketones. 

This reaction was first reported by Nenitzescu in 1931. It is the formation of an a,p-unsaturated ketone directly by aluminum chloride-promoted acylation of alkenes with acyl halides. Therefore, it is known as the Darzens-Nenitzescu reaction (or Nenitzescu reductive acylation), or Nenitzescu acylation. Under such reaction conditions, Nenitzescu prepared 2-butenyl methyl ketone from acetyl chloride and 1-butene and dimethylacetylcyclohex-ene from acetyl chloride and cyclooctene. However, in the presence of benzene or hexane, the saturated ketones are often resolved, as supported by the preparation of 4-phenyl cyclohexyl methyl ketone from the reaction of cyclohexene and acetyl chloride in benzene, and the synthesis of 3- or 4-methylcyclohexyl methyl ketone by refluxing the mixture of cycloheptene and acetyl chloride in cyclohexane or isopentane. This is probably caused by the intermolecular hydrogen transfer from the solvent. In addition, owing to its intrinsic strain, cyclopropyl group reacts in a manner similar to an oleflnic functionality so that it can be readily acylated. It should be pointed out that under various reaction conditions, the Darzens-Nenitzescu reaction is often complicated by the formation of -halo ketones, 3,)/-enones, or /3-acyloxy ketones. This complication can be overcome by an aluminum chloride-promoted acylation with vinyl mercuric chloride, resulting in a high purity of stereochemistry. ... 

Other references related to the Darzens-Nenitzescu reaction are cited in the literature. 

Several name reactions are promoted by AICI3. For example, the Darzens-Nenitzescu reaction is simply the acylation of alkenes. The Ferrario reaction generates phenoxathiins from diphenyl ethers (eq 19) The rearrangement of acyloxy aromatic systems is known as the Fries rearrangement (eq 20). Aryl aldehydes are produced by the Gatterman aldehyde synthesis (eq 21). The initial step of the Haworth phenanthrene synthesis makes use of a Friedel-Crafts acylation. The acylation of phenolic cort tounds is called the Houben-Hoesch reaction (eq 22). The Leuckart amide s)oithesis generates aryl amides from isocyanates (eq 23). ... 

Diene)tricarbonyliron complexes are able to react with a variety of nucleophiles, mediated by a Lewis acid. The Darzens-Nenitzescu reaction was utilized to prepare i7" -dienetricarbonyliron complexes containing carbonyl groups. Lewis acid-catalyzed nucleophilic additions have been reported to occur at carbonyl functionalities adjacent to an iron-complexed diene. In a separate study, facile racemization or epimerization was observed... 

Several name reactions are promoted by AICI3. For example, the Darzens-Nenitzescu reaction is simply the acylation of alkenes. 

Alcohols and alkenes are also useful alkylating agents. Some classify the latter reactions as Darzens-Nenitzescu Alkylation The Reaction ... 

Nenitzescu (see Darzens-Nenitzescu Synthesis of Ketones) Nenitzescu Indole Synthesis Nenitzescu Reductive Acylation Nicholas Reaction... 

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