Nitriles aromatic acylation

H-Bond Acceptor (HBA) Acyl chlorides Acyl fluorides Hetero nitrogen aromatics Hetero oj gen aromatics Tertiary amides Tertiary amines Other nitriles Other nitros Isocyanates Peroxides Aldehydes Anhydrides Cyclo ketones Ahphatic ketones Esters Ethers Aromatic esters Aromatic nitriles Aromatic ethers Sulfones Sulfolanes... 

Acyl nitroso compounds react with 1, 3-dienes as N-O heterodienophiles to produce cycloadducts, which have found use in the total synthesis of a number of nitrogen-containing natural products [21]. The cycloadducts of acyl nitroso compounds and 9,10-dimethylanthracene (4, Scheme 7.3) undergo thermal decomposition through retro-Diels-Alder reactions to produce acyl nitroso compounds under non-oxidative conditions and at relatively mild temperatures (40-100°C) [11-14]. Decomposition of these compounds provides a particularly clean method for the formation of acyl nitroso compounds. Photolysis or thermolysis of 3, 5-diphenyl-l, 2, 4-oxadiazole-4-oxide (5) generates the aromatic acyl nitroso compound (6) and ben-zonitrile (Scheme 7.3) [22, 23]. Other reactions that generate acyl nitroso compounds include the treatment of 5 with a nitrile oxide [24], the addition of N-methyl morpholine N-oxide to nitrile oxides and the decomposition of N, O-diacylated or alkylated N-hydroxyarylsulfonamides [25-29]. 

Decarbonylation of acyl cyanides.9 Aromatic acyl cyanides, which are easily obtained by oxidation of cyanohydrins with /-butyl hydroperoxide catalyzed by RuC12[P(C6H5)3]3, undergo decarbonylation to nitriles in high yield when heated in the presence of Pd(0). 

The organoindium reagent, prepared from indium metal and bromoacetonitrile, reacts with carbonyl compounds in the presence of chlorotrimethylsilane to give /3-hydroxy nitriles (Scheme 93),336 337 Similarly, indium-mediated coupling of bromoacetonitrile or 2-bromopropionitrile with a variety of aromatic acyl cyanides affords the corresponding aromatic a-cyanoketones in moderate to good yields under mild and neutral conditions (Equation (86)).338 Carbonyl compounds are efficiently transformed into 2,2-dichloro-3-hydroxynitriles by the action of trichloroaceto-nitrile and indium(i) bromide (Scheme 94).339 Bromocyanomethylation of carbonyl compounds is also achieved by the reaction of dibromoacetonitrile and indium(i) bromide.340... 

The conversion of aliphatic and aromatic acyl halides to a keto nitriles has been effected by heating the halides with dry metallic cyanides, of which cuprous cyanide has given the most satisfactory results (60-87%). The acyl bromides rather than the chlorides ate preferred, at least in the formation of aliphatic compounds. Thus, pyruvonitrile is prepared in 77% yield from acetyl bromide and cuprous cyanide whereas no product is obtained if acetyl chloride is employed. Benzoyl cyanide is made in 65% yield by heating the corresponding acyl chloride with cuprous cyanide. "... 

SnCU-promoted addition of malonates and bromomalonates to simple nitriles (not electron-deficient) gives a,/8-dehydro-/3-amino acid derivatives (Eq. 44) [74]. SnCU is the Lewis acid of choice for the condensation of aroyl chlorides with sodium isocyanate, affording aroyl isocyanates in 70-85 % yields [75]. Non-aromatic acyl chlorides react under more variable reaction conditions. 

The palladium-catalyzed decarbonylation of aromatic acyl cyanides proceeds at 120 °C to give the corresponding nitriles in excellent yield. Since acyl cyanides are readily prepared by the ruthenium-catalyzed oxidation of cyanohydrins with BuKDOH this represents a good method for the conversion of aldehydes to nitriles under mild conditions (Scheme 29). 

Aromatic and Vinyl Nitriles. Aromatic haUdes (Br, I) have been converted into nitriles in excellent yields by Pd(Ph3P)4 catalysis in the presence of Sodium Cyanide Alumina,Potassium Cyanide, or Cyanotrimethykilane (eq 24). While the latter two procedures require the use of Arl as substrates, a more extensive range of substituents are tolerated than the alternative method employing ArBr. A Pd(Ph3P)4-catalyzed extrasion of CO from aromatic and heteroaromatic acyl cyanides (readily available from cyanohydrins) at 120 °C provides aryl nitriles in excellent yields (eq 25). ... 

Hoesch reaction. In most cases, a Lewis acid is necessary zinc chloride is the most common. The reaction is generally useful only with phenols, phenolic ethers, and some reactive heterocyclic compounds (e.g., pyrrole), but it can be extended to aromatic amines by the use of BCls. Acylation in the case of amines is regioselectively ortho. Monohydric phenols, however, generally do not give ketones " but are attacked at the oxygen to produce imino esters. Many nitriles... 

Salts of aliphatic or aromatic carboxylic acids can be converted to the corresponding nitriles by heating with BrCN or CICN. Despite appearances, this is not a substitution reaction. When R COO was used, the label appeared in the nitrile, not in the C02, and optical activity in R was retained. The acyl isocyanate... 

Acylation of aromatic rings with nitriles (Hoesch)... 

Carbon monoxide, hydrogen cyanide, and nitriles also react with aromatic compounds in the presence of strong acids or Friedel-Crafts catalysts to introduce formyl or acyl substituents. The active electrophiles are believed to be dications resulting from diprotonation of CO, HCN, or the nitrile.64 The general outlines of the mechanisms of these reactions are given below. 

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

Buchwald and co-workers reported a directed zirconium-mediated /// -acylation of various aromatic compounds, bearing a directing group, with different nitriles.150 One representative example is shown in Equation (14). 

Stetter expanded Umpolung reactivity to include the addition of acyl anion equivalents to a,P-unsaturated acceptors to afford 1,4-dicarbonyls Eq. 5a [57-60]. Utilizing cyanide or thiazolylidene carbenes as catalysts, Stetter showed that a variety of aromatic and aliphatic aldehydes act as competent nucleophilic coupling partners with a wide range of a,p-unsaturated ketones, esters, and nitriles [61]. The ability to bring two different electrophilic partners... 

In addition to the methods previously described in this chapter, there are numerous other ways to make aldehydes and ketones, depending on the stcirting materials. These include using alkynes, doing a Friedel-Crtifts acylation of an acid chloride and an aromatic compound, using organic nitriles, and the use of carboxylic acid. We examine each of these in the following sections. 

The lower members of the homologous series of 1. Alcohols 2. Aldehydes 3. Ketones 4. Acids 5. Esters 6. Phenols 7. Anhydrides 8. Amines 9. Nitriles 10. Polyhydroxy phenols 1. Polybasic acids and hydro-oxy acids. 2. Glycols, poly-hydric alcohols, polyhydroxy aldehydes and ketones (sugars) 3. Some amides, ammo acids, di-and polyamino compounds, amino alcohols 4. Sulphonic acids 5. Sulphinic acids 6. Salts 1. Acids 2. Phenols 3. Imides 4. Some primary and secondary nitro compounds oximes 5. Mercaptans and thiophenols 6. Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides 7. Some diketones and (3-keto esters 1. Primary amines 2. Secondary aliphatic and aryl-alkyl amines 3. Aliphatic and some aryl-alkyl tertiary amines 4. Hydrazines 1. Unsaturated hydrocarbons 2. Some poly-alkylated aromatic hydrocarbons 3. Alcohols 4. Aldehydes 5. Ketones 6. Esters 7. Anhydrides 8. Ethers and acetals 9. Lactones 10. Acyl halides 1. Saturated aliphatic hydrocarbons Cyclic paraffin hydrocarbons 3. Aromatic hydrocarbons 4. Halogen derivatives of 1, 2 and 3 5. Diaryl ethers 1. Nitro compounds (tertiary) 2. Amides and derivatives of aldehydes and ketones 3. Nitriles 4. Negatively substituted amines 5. Nitroso, azo, hy-drazo, and other intermediate reduction products of nitro com-pounds 6. Sulphones, sul-phonamides of secondary amines, sulphides, sulphates and other Sulphur compounds... 

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