Ketones, cyclopropyl phenyl reduction

Acceptor-substituted cyclopropanes are susceptible to bond cleavage upon reduction. When (2-phenylcyclopropyl)phenyl ketone (1) was submitted to electrolysis with a controlled potential of - 1.2 V in ethanol, 4-phenylbutyrophenone (2) was obtained. Interestingly, the cyclopropyl phenyl ketone 3, that lacks the phenyl substituent on the ring, resisted ring opening and gave the carbinol 4 as the product. 

Unusual reduction of eyclopropyl phenyl ketone. Cyclopropyl ketones are reduced by Li-NHa with cleavage of the cyclopropane ring for example, cyclopropyl methyl ketone is reduced to pentanone-2 and pentanol-2. Unexpectedly cyclopropyl phenyl ketone is reduced without cleavage (equation I). ... 

Triethylsilane in trifluoroacetic acid has proved to be a mild and selective reducing agent for the conversion of aryl and diaryl ketones into the corresponding arenes however, with activated benzaldehydes, e.g, 4-MeCeH4-CHO, Friedel-Crafts alkylation competes with reduction. Reduction of phenyl cyclobutyl ketone and phenyl cyclopropyl ketone gives low yields (36 and ca. 25%, respectively) of the corresponding benzylcycloalkanes [the former reaction also affords phenylcydo-pentane (ca. 42%) via ring-expansion] and with ortAo-benzoylbenzoic acid and 3-benzoyIpropanoic acid the lactones (11) (100%) and (12) (86%), respectively, are formed. ... 

Overlap control by steric factors of phenyl substituents in cyclopropanes additionally containing a carbonyl group have been described by Zimmerman and coworkers in the liquid ammonia reduction of the isomeric diphenyl cyclopropyl ketones cis- and trans-137. 

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. ... 

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