Benzene, acylation hydrogenation

Another recent patent (22) and related patent application (31) cover incorporation and use of many active metals into Si-TUD-1. Some active materials were incorporated simultaneously (e.g., NiW, NiMo, and Ga/Zn/Sn). The various catalysts have been used for many organic reactions [TUD-1 variants are shown in brackets] Alkylation of naphthalene with 1-hexadecene [Al-Si] Friedel-Crafts benzylation of benzene [Fe-Si, Ga-Si, Sn-Si and Ti-Si, see apphcation 2 above] oligomerization of 1-decene [Al-Si] selective oxidation of ethylbenzene to acetophenone [Cr-Si, Mo-Si] and selective oxidation of cyclohexanol to cyclohexanone [Mo-Si], A dehydrogenation process (32) has been described using an immobilized pincer catalyst on a TUD-1 substrate. Previously these catalysts were homogeneous, which often caused problems in separation and recycle. Several other reactions were described, including acylation, hydrogenation, and ammoxidation. 

Isoquinoline can be reduced quantitatively over platinum in acidic media to a mixture of i j -decahydroisoquinoline [2744-08-3] and /n j -decahydroisoquinoline [2744-09-4] (32). Hydrogenation with platinum oxide in strong acid, but under mild conditions, selectively reduces the benzene ring and leads to a 90% yield of 5,6,7,8-tetrahydroisoquinoline [36556-06-6] (32,33). Sodium hydride, in dipolar aprotic solvents like hexamethylphosphoric triamide, reduces isoquinoline in quantitative yield to the sodium adduct [81045-34-3] (25) (152). The adduct reacts with acid chlorides or anhydrides to give N-acyl derivatives which are converted to 4-substituted 1,2-dihydroisoquinolines. Sodium borohydride and carboxylic acids combine to provide a one-step reduction—alkylation (35). Sodium cyanoborohydride reduces isoquinoline under similar conditions without N-alkylation to give... 

The aromatic sulfonyl chlorides which have no a-hydrogen and thus cannot form sulfenes give acylic sulfones. Thus 1-piperidinopropene on reaction with benzene sulfonyl chloride (9J) gave 2-benzenesulfonyl-l-piperidinopropene (153). Similarly the enamine (28) reacts with p-toluene-sulfonyl chloride to give the 2-p-toluenesulfonylcyclohexanone (154) on hydrolysis (/OS). 

The most notable chemistry of the biscylopen-tadienyls results from the aromaticity of the cyclopentadienyl rings. This is now far too extensively documented to be described in full but an outline of some of its manifestations is in Fig. 25.14. Ferrocene resists catalytic hydrogenation and does not undergo the typical reactions of conjugated dienes, such as the Diels-Alder reaction. Nor are direct nitration and halogenation possible because of oxidation to the ferricinium ion. However, Friedel-Crafts acylation as well as alkylation and metallation reactions, are readily effected. Indeed, electrophilic substitution of ferrocene occurs with such facility compared to, say, benzene (3 x 10 faster) that some explanation is called for. It has been suggested that. 

A heterocyclic ring may be used in place of one of the benzene rings without loss of biologic activity. The first step in the synthesis of such an agent starts by Friedel-Crafts-like acylation rather than displacement. Thus, reaction of sulfenyl chloride, 222, with 2-aminothiazole (223) in the presence of acetic anhydride affords the sulfide, 224. The amine is then protected as the amide (225). Oxidation with hydrogen peroxide leads to the corresponding sulfone (226) hydrolysis followed by reduction of the nitro group then affords thiazosulfone (227). ... 

A ketone can also be formed with a Friedel-Crafts acylation. The process requires an acid chloride and an aromatic compound. An aldehyde can t be formed by this procedure because the appropriate acid chloride, formyl chloride (HCOCl), is unstable and decomposes to carbon monoxide and hydrogen chloride. Figure 10-12 illustrates the preparation of acetophenone from benzene and acetyl chloride. 

The most frequently used method for the preparation of isoquinoline Reissert compounds is treatment of an isoquinoline with acyl chloride and potassium cyanide in water or in a dichloromethane-water solvent system. Though this method could be successfully applied in a great number of syntheses, it has also some disadvantages. First, the starting isoquinoline and the Reissert compound formed in the reaction are usually insoluble in water. Second, in the case of reactive acyl halides the hydrolysis of this reaction partner may became dominant. Third, the hydroxide ion present could compete with the cyanide ion as a nucleophile to produce a pseudobase instead of Reissert compound. To decrease the pseudobase formation phase-transfer catalysts have been used successfully in the case of the dichloromethane-water solvent system, resulting in considerably increased yields of the Reissert compound. To avoid the hydrolysis of reactive acid halides in some cases nonaqueous media have been applied, e.g., acetonitrile, acetone, dioxane, benzene, while utilizing hydrogen cyanide or trimethylsilyl cyanide as reactants instead of potassium cyanide. 

Electrophilic aromatic substitution is a reaction where a hydrogen atom in an aromatic system, e.g. benzene, is replaced by an electrophile. Some of the important electrophilic substitution reactions are Friedel-Crafts alkylation and acylation, nitration, halogenation and sulphonation of benzene. 

Another important path of research, especially to organic chemists, resulted from a discovery by Woodward, Rosenblum, and Whiting at Harvard University in 1952 (128). These investigators noted the failure of ferrocene to undergo Diels-Alder reactions and its resistance to catalytic hydrogenation. They reasoned that because of its remarkable stability, ferrocene might behave like an aromatic substance. These suppositions proved to be the case, as ferrocene was readily acylated under Friedel-Crafts conditions to form acyl derivatives. Indeed, the name ferrocene was given to biscyclopentadienyliron because of its chemical similarity to benzene (128). 

In an attempt to resolve this question of stereochemistry and also to determine whether or not the decarbonylation of an acid chloride containing a f3 hydrogen takes place stereospecifically, erythro- (XI) and fhreo-2,3-diphenylbutanoyl chlorides (XII), obtained by the reaction of the known acids (13, 14) with oxalyl chloride, were synthesized. The reaction of these acid chlorides (see Reaction 8) with chlorotris( triphenyl-phosphine) rhodium gave the corresponding acyl complexes of type lib [R = C6H5CH(CH3)CH(C6H5)]. Decarbonylation of the erythro- cy complex in benzene at 30 °C gave a 90% yield of frans-a-methylstilbene while decarbonylation of the threo-acyl complex under similar reaction... 

Acylation of compounds of type 63 was carried out with acid anhydrides,107 occasionally in the presence of sodium acetate.103,282 Acylation was also carried out with acid chlorides in benzene or chloroform, and either in the presence of pyridine121,282 or in the presence of potassium hydrogen carbonate.51 Reactions starting from the sodium salt of 63 (R = H) were also carried out.167 The formation of more than one product has usually been reported. 

Triphenylsilyl zirconium and hafnium derivatives have been prepared from the silyl lithium species. Triphenylsilyl bis(cyclopentadienyl) zirconium chloride undergoes carbonyl insertion under pressure of carbon monoxide (100 psi) to give the corresponding acyl zirconium species which, upon treatment with anhydrous hydrogen chloride in a benzene matrix at —196 °C and warming to room temperature, gives rise to formyl triphenylsilane55. 

Symmetrical (but not unsymmetrical) anhydrides are useful acylating reagents as milder alternatives to acyl halides. The most convenient procedure for their preparation involves the interaction in benzene solution of the acyl halide with the corresponding carboxylic acid in the presence of pyridine, which removes the hydrogen chloride liberated as the insoluble pyridinium chloride. 

Other diprotonated acyl-pyridines have likewise been studied.61 In studies of 5-, 6-, 7-, and 8-hydroxyquinolines and 5-hydroxyisoquinoline, dicationic intermediates like 185 (Table 4) were found to be involved in superacid catalyzed reactions with benzene and cyclohexane.59 For example, 8-hydroxyquinoline (187) reacts in CF SOsH-SbFs to generate dications (188 and 189) and undergoes ionic hydrogenation in the presence of cyclohexane (eq 64). Compound 187 also reacts with benzene in suspensions of aluminum halides (eq 65). 

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