Nitriles aryl, hydrolysis

Several approaches to the synthesis of the tetrahydrobenzazepine ring system have been described, and excellent methods exist for the preparation of aryl substituted tetrahydrobenzazepines. However, benzazepines that are either unsubstituted or alkyl-substituted on the azepine ring are much less readily obtainable. For instance, the benzazepinone, synthesized by this procedure, was originally isolated, in tow yield, from the mixture of photoproducts obtained from the irradiation of N-[3-(3,4-dimethoxyphenyl)]propyl chloroacetamide. Preparative approaches to the benzazepinones have required multiple steps starting from an N-phenylethylacetamide and involving chloromethylation, cyanide displacement, nitrile solvolysis, hydrolysis to the amino acid and cyclization.7 The f-alkyl derivatives are... 

The industrial synthesis of ibuprofen is a well-known case study for green chemistry . [190] The original Boots route, starting from benzene, comprised seven steps, p-lsobutylacetophenone is accessible by alkylation of benzene with isobutene, followed by a Friedel-Crafts acylation with acetic chloride. Homologation to the corresponding aryl-propionaldehyde is achieved by a Darzens reaction. Transformations via the oxime and nitrile, and hydrolysis of the latter, finally give ibuprofen. 

With the above methodology in hand, a similar strategy was attenq)ted for the synthesis of the aryl acetic acid 7 (Scheme 7). The aniline 5 was treated with 2,5-dimethoxytetrahy ofuran in toluene and acetic acid to get the W-aryl pyrrole 28. The Vilsmeier/Triedel-Crafts acylation of 28 followed by decarbonylation afforded the keto ester 30. However, the reduction of the keto ester proved to be difficult. Most of the general methods employed for the reduction of ketones gave a mixture of products. However, a two step process involving the formation of the thioketal 31 followed by desulfurization with Ni proved to be successful. Although, the standard Wolff-Kishner conditions could not be employed in the system due to the susceptibility of the nitrile to hydrolysis, a modified Wolff-Kishner reduction (8) proved to be fruitful. 

By the hydrolysis of nitriles. The nitriles may be easily prepared either from amines by the Sandmeyer reaction (Section IV,66) or by the action of cuprous cyanide upon aryl halides (compare Section IV,163). Benzyl cyanide... 

Because cyano groups may be hydrolyzed to carboxylic acids (Section 20 19) the Sand meyer preparation of aryl nitriles is a key step m the conversion of arylammes to sub stituted benzoic acids In the example just cited the o methylbenzomtnle that was formed was subsequently subiected to acid catalyzed hydrolysis and gave o methylbenzoic acid in 80-89% yield... 

The tetrachloroferrate or tetralluoroborate salts of alkylated alkyl- or aryl-nitriles (nitrilium ions) are reduced to imines with triethylsilane. Subsequent hydrolysis of the intermediate imines leads to aldehydes in good yields, thus providing an excellent overall route to aldehydes from nitriles (Eq. 338).28,562... 

The 6//-l,3-thiazin-6-iminium hydroperchlorate salts 78-81 give interesting products when treated with nucleophiles <2003H(60)2273>. Hydrolysis of 6-imino-6//-l,3-thiazine hydroperchlorate 78 affords (2Z,4Z)-2-cyano-5-hydroxy-5-phenyM-azapenta-2,4-dienethioamide 82 in excellent yield, while treatment with morpholine gives 2-(morpholinomethylene)malononitrile 83 and thiobenzamide. The 5-(ethoxycarbonyl) -(methylthio)-2-aryl-6/7-l,3-thiazin-6-iminium salts 79 and 80 react with hydroxide or morpholine to afford ethyl 4-(methylthio)-2-aryl-6-thioxo-l,6-dihydropyrimidine-5-carboxylates 84 and 85. In the case of the 4-chloro analogue 80, the (Z)-ethyl 2-(5-(4-chlorophenyl)-37/-l,2,4-dithiazol-3-ylidene)-2-cyanoacetate 87 is also formed for the reaction with sodium hydroxide. The 1,2,4-dithiazoles 86 and 87 can be obtained as the sole product when 79 and 80 are treated with sodium acetate in DMSO. Benzoxazine 88 is isolated when the iminium salt 81 is treated with morpholine or triethylamine. Nitrile 89 is formed as a ( /Z)-mixture when 6-imino-67/-l,3-thiazine hydroperchlorate 79 is reacted with triethylamine and iodomethane in methanol <2003H(60)2273>. 

Usually, after hydrolysis, the alcohol is the product, but sometimes (especially with aryl aldehydes) elimination follows directly and the product is an olefin. By the use of Bu,P along with Zn, the olefin can be made the main product,454 making this an alternative to the Wittig reaction (6-47). Since Grignard reagents cannot be formed from a-halo esters, the method is quite useful, though there are competing reactions and yields are sometimes low. A similar reaction (called the Blaise reaction) has been carried out on nitriles 455... 

Nitriles are well known to undergo acid and alkaline hydrolysis (Figure 13.5), but there is only one recent report of neutral hydrolysis. Thus, methacrylonitrile, even though it is conjugated with an alkenyl substituent, should undergo both acid-catalyzed and base-mediated hydrolysis via a pathway similar to that for alkyl and aryl nitriles. The amide is a likely intermediate product for nitrile hydrolysis, but it is reactive as well and can undergo acid- and base-mediated hydrolysis to the carboxylic acid and ammonia. The... 

The first enantioselective catalytic Strecker reaction of ketoimines to give chiral quaternary cyanohydrins was demonstrated by the Jacobsen group using 45b (Scheme 6.7) [41]. A series of substituted aryl and aliphatic N-benzyl methylketo-imines (48) reacted with HCN in the presence of 45b to provide essentially quantitative yields of the Strecker adducts in high optical purities (70-95% ee). The adducts were crystalline, and their recrystallization from hexanes increased their enantiopurities to >99.9% ee. The a-quaternary Strecker adducts (49) could be converted to a-quaternary a-amino acids through formamide protection of the secondary amine, followed by sequential hydrolysis of the nitrile and the formamide, followed by hydrogenolytic debenzylation. 

The N-alkylation of amides followed by hydrolysis furnishes a good route for making secondary amines. The formyl, acetyl, and aryl-sulfonyl " derivatives of amines are best suited for alkylation (method 358). Hydrolysis is accomplished by refluxing concentrated hydrochloric acid alone or in acetic acid. N-Alkyl-formamides prepared by the addition of olefins to nitriles (method 355) are hydrolyzed with aqueous alkali. Similar hydrolytic procedures... 

A wide variety of other alcohol substrates has been resolved, including aryl substituted secondary alcohols, - a-alkyl-P-hydroxy esters, P-hydroxy nitriles, and fluoroorganic compounds. Active chloroacetate esters are commonly used to speed up the hydrolysis reactions, as exemplified in eq 2 Primary acyclic alcohols possessing a stereogenic center that have been resolved include 2,3-epoxy alcohols, - 2-amino alcohols, and crown ethers. ... 

The previous cycloaddition reaction discussed is believed to proceed through an aldimine anion (19). Such delocalized anions can also be generated by treatment of suitable aldimines with a strong base. Subsequent cyclocondensation with a nitrile produces imidazoles [25-28]. The 2-azaallyl lithium compounds (19) are made by treatment of an azomethine with lithium diiso-propylamide in THF-hexane ( 5 1) (Scheme 4.2.9) [29. To stirred solutions of (19) one adds an equimolar amount of a nitrile in THF at —60°C. Products are obtained after hydrolysis with water (see also Section 2.3). If the original Schiff base is disubstituted on carbon, the product can only be a 3-imidazoline, but anions (19) eliminate lithium hydride to give aromatic products (20) in 37-52% yields (Scheme 4.2.9). It is, however, not possible to make delocalized anions (19) with R = alkyl, and aliphatic nitriles react only veiy reluctantly. Examples of (20) (Ar, R, R, yield listed) include Ph, Ph, Ph, 52% Ph, Ph, m-MeCeUi, 50% Ph, Ph, p-MeCeUi, 52% Ph, Ph, 3-pyridyl, 47% Ph, Ph, nPr, 1% [25]. Closely related is the synthesis of tetrasubstituted imidazoles (22) by regioselective deprotonation of (21) and subsequent reaction with an aryl nitrile. Even belter yields and reactivity are observed when one equivalent of potassium t-butoxide is added to the preformed monolithio anion of (21) (Scheme 4.2.9) [30]. 

Sequential [3+2] cycloaddition/silicon-based cross-coupling reactions allowed for the synthesis of 3,4,5-trisubsti-tuted isoxazoles. Regioselective 1,3-dipolar cycloaddition reactions between alkynyldimethylsilyl ethers 400 and ethyl or phenyl nitrile oxides, generated in situ from 1-nitropropane and A -hydroxybenzene carboximidoyl chloride, respectively, gave as predominant products after hydrolysis isoxazol-4-ylsilanols 401, converted into 4-arylisoxazoles 402 by cross-coupling with a variety of aryl iodides (Scheme 97) <2005JOC2839>. 

From Aryl Cyanides Acid Nitriles),— The aromatic cyanides which were simply referred to as substitution products (p. 521) are, of course, like the aliphatic cyanides, nitriles of acids which they yield on hydrolysis. 

A related reaction involves a-substituted aryl nitriles having a sufficiently acidic a hydrogen, which can be converted to ketones by oxidation with air under phase transfer conditions. The nitrile is added to NaOH in benzene or DMSO containing a catalytic amount of triethylbenzylammonium chloride (TEBA). " This reaction could not be applied to aliphatic nitriles, but an indirect method for achieving this conversion is given in 19-60. a-Dialkylamino nitriles can be converted to ketones, R2C(NMe2)CN —> R2C=0, by hydrolysis with Q1SO4 in aqueous methanol or by autoxidation in the presence of r-BuOK. ... 

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