Synthesis of Anilides

Hsung et al. reported subsequently that when achiral ynamides 103 and a chiral rhodium(I) catalyst were employed instead of chiral ynamides 101 and Wilkinson s 

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FIGURE 8.4 Synthesis of anilides of A-protected glutamic acid by aminolysis of the anhydride in dimethylsulfoxide, which gives the a-isomers, and in benzene, which gives the a-isomers.18 X = H, Cl, OMe, N02. 

When Bergmann and Fraenkel-Conrat (17) described the synthesis of anilides by papain, they also noted that benzoylglycine... 

When bromoacetyl chloride is used instead of bromoacetic acid, the anilide 33 is formed at the first stage. Its subsequent cyclization also leads to 32. This approach to benzotellurazinone is similar to that developed for the synthesis of 2//-l,4-benzothiazin-3(4//)-ones (66CJC1247). Significantly, attempts to isolate the intermediate sulfonium salts analogous to 30 were unsuccessful. 

A synthesis of 4-methylquinolines 277 by the modified Fiiedlander reaction from ort/io-lithiated anilides 276 and 4-methoxybut-3-en-2-one (—20°C, THF, pentane, 2 h) in 14-17% yields (in the cyclization stage) has been described (91JOC7288). 

The oxidative formation of p-benzoquinones from anilides such as 7-108 was used for the synthesis of the core scaffold of the natural products elisabethin A (7-106) and pseudopterosin A aglycone (7-107) (Scheme 7.30). Exposure of anilide 7-108 to DMP [53] led to the formation of the o-imidoquinone 7-109, which underwent an intramolecular Diels-Alder reaction to give 7-110 in 28% yield after hydration. In a competitive pathway, the p-quinone 7-111 is also formed from 7-108, which on heating in toluene again underwent an intramolecular Diels-Alder reaction to give cycloadduct 7-112 in 25% overall yield. Hydrolysis of 7-112 furnished the carbocyclic skeleton 7-113 of elisabethin A (7-106). 

Amination of aromatic nitro compounds is a very important process in both industry and laboratory. A simple synthesis of 4-aminodiphenyl amine (4-ADPA) has been achieved by utilizing a nucleophilic aromatic substitution. 4-ADPA is a key intermediate in the rubber chemical family of antioxidants. By means of a nucleophibc attack of the anilide anion on a nitrobenzene, a o-complex is formed first, which is then converted into 4-nitrosodiphenylamine and 4-nitrodiphenylamine by intra- and intermolecular oxidation. Catalytic hydrogenation finally affords 4-ADPA. Azobenzene, which is formed as a by-product, can be hydrogenated to aniline and thus recycled into the process. Switching this new atom-economy route allows for a dramatic reduction of chemical waste (Scheme 9.9).73 The United States Environmental Protection Agency gave the Green Chemistry Award for this process in 1998.74... 

The condensation of anilides or enamides with nitriles was developed as a general method for the synthesis of pyrimidines or quinazolines such as 35 and 36 <06JACS 14254>. 

Synthesis of isatin 109 derivatives readily proceeds from anilide-derived oximes 108 by interaction with sulfuric acid (equation 46) ... 

An alternative to the synthesis of proteins by classical fragment synthesis in solution or by solid-phase synthesis on a support is the use of enzyme-catalyzed condensation of amino acids or peptides. This possibility was first demonstrated in 1938 91 with the synthesis of poorly soluble benzoyl-leucyl-leucine anilide by papain catalysis. After many years, this approach was extended to the preparation of peptide hormones such as Leu-enkephalin 92 and dynorphin(l -8).[93 This was made possible by the use of highly purified enzymes and by careful control of reaction conditions. The basic principles of protease-catalyzed peptide bond formation have been discussed.194 ... 

An unusual rearrangement following cyclization using a masked a-carbonyl equivalent, 2-anilino-2-ethoxy-3-oxothiobutanoic acid anilide 118, to form 6,7-disubstituted pteridine 119 by simply refluxing in ethanol for 3h was reported (Scheme 24) <2002JOC4526>. The synthesis of pyridopyrazine and related compounds using 39 was also discussed. 

Processes include the Fischer indole synthesis from arylhydrazones and related sigmatropic syntheses, reductive evclizations of nitni compounds, the Madelung synthesis from anilides and related base-cululyxed condensations. and transition-metal catalyzed cyclizations,... 

Simple Aromatic Amines.—Crystalline anilides of 2-desoxy-D-galac-tose,223 2-desoxy-D-glucose,120 223 2-desoxy-D-xylose,60 and 2-desoxy-D-158 and -L-ribose112 have been obtained by the usual method of synthesis of... 

Several reactive chloro compounds have been used to attempt to effect the controlled monochlorination of aromatic amines. One such reagent is N-chlorosuccinimide, with which the chlorination of aniline, for example, can be largely restricted to monosubstitution, although a mixture of isomers (orthopara, 1.9 1) is obtained.24 One approach to the achievement of specific ortho chlorination is illustrated by the synthesis of o-chlorobenzanilide (Expt 6.61), readily hydrolysable to o-chloroaniline. The anilide is formed, by a type of Swi mechanism indicated below, when AT-phenylhydroxylamine is benzoylated and the product is treated with thionyl chloride.25 The reaction has been successfully applied to several substituted JV-phenylhydroxylamines, prepared by the controlled reduction of the corresponding substituted nitro compounds (cf. Expt 6.87). 

The Dess-Martin periodinane 8 is also able to oxidize aromatic compounds to the corresponding quinones. The presence of water is important and, starting from anilides 42 substituted in the 2-position, the rare class of ortho-imido-quinones 43 is accessible, Scheme 21. It has been shown that compounds of type 43 are interesting building blocks and can lead to polycyclic molecules of diverse molecular architecture [95,96]. They can undergo subsequent Diels-Alder reactions and intramolecular versions have been used for a rapid access to natural products and for synthesis of scaffolds for further manipulation.para-Quinones 45 are also easily accessible, however, only in modest yields by reacting 4-sub-stituted anilines 44 under the same reaction conditions, Scheme 21 [97]. 

Total Synthesis via Oxidation Reactions of Anilides with... 

Fig. 5.63. Synthesis of diphenylamine via an intermediate benzyne. The phenyl-lithium that has been formed in situ serves to generate lithium anilide. In the synthesis presented here lithium anilide plays the same role as sodium hydroxide in the reaction given in Figure 5.61 and potassium-tert-butoxide in the reaction shown in Figure 5.62.

Direct synthesis of atropisomeric benzamides and anilides from prochiral precursors has been reported using chiral-amide-mediated deprotonation of 2,6-dimethyl-substituted ben-zamide and anilide chromium complexes. A screening of amides revealed that (R,R) 3 was the most selective in the deprotonation of the benzylic methyl groups (Scheme 51)92 94. 

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