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Nitriles, preparation from amides

Pictet-Spengler cyclization of L-tryptophan with formaldehyde afforded the monochiral carboxylic acids 20a,b, whereas cyclization with acetaldehyde yielded the diastereomeric carboxylic acids 21a,b (23). Acids 20a,b with a hydrogen at C-1 are enantiomers, but acids 21a,b are diaste-reomers the cis isomer 21a was the major reaction product when the cyclization of L-tryptophan with acetaldehyde was carried out in the presence of sulfuric acid. Direct removal of the carboxy group in these acids is difficult, but it can be accomplished in several steps dehydration of the amides prepared from the acids with phosphorus oxychloride affords nitriles, and the nitrile group can be removed by reduction with sodium borohydride in pyridine-ethanol (31). [Pg.126]

The formation of amide chlorides from nitriles and hydrogen halides under anhydrous conditions is a well-known reaction of wide scope7- There has been some confusion on the nature of the reaction products, but it has turned out that the isolable species are amide chlorides. The thermal stability of the addition products strongly depends on the acidity of the hydrogen halide used. Iodides are more stable than bromides, which in turn are more stable than the chlorides. As a consequence, thermally stable HQ adducts (38 equation 22) can be prepared if Lewis acids ate present, which incorporate the chlorine anion to give a less basic anion (39). [Pg.497]

Nitriles and simple amides differ in physical properties the former are liquids or low-melting Solids, whilst the latter are generally solids. If the amide is a solid and insoluble in water, it may be readily prepared from the nitrile by dissolving in concentrated sulphuric acid and pouring the solution into water ... [Pg.1075]

Nitdles may be prepared by several methods (1). The first nitrile to be prepared was propionitdle, which was obtained in 1834 by distilling barium ethyl sulfate with potassium cyanide. This is a general preparation of nitriles from sulfonate salts and is referred to as the Pelou2e reaction (2). Although not commonly practiced today, dehydration of amides has been widely used to produce nitriles and was the first commercial synthesis of a nitrile. The reaction of alkyl hahdes with sodium cyanide to produce nitriles (eq. 1) also is a general reaction with wide appHcabiUty ... [Pg.217]

Ketenimines are usually prepared from carboxyHc acid derivatives such as amides and imino chlorides via elimination and from nitriles via alkylation with alkyl haHdes under strong basic conditions (21,64). [Pg.476]

A thioamide of isonicotinic acid has also shown tuberculostatic activity in the clinic. The additional substitution on the pyridine ring precludes its preparation from simple starting materials. Reaction of ethyl methyl ketone with ethyl oxalate leads to the ester-diketone, 12 (shown as its enol). Condensation of this with cyanoacetamide gives the substituted pyridone, 13, which contains both the ethyl and carboxyl groups in the desired position. The nitrile group is then excised by means of decarboxylative hydrolysis. Treatment of the pyridone (14) with phosphorus oxychloride converts that compound (after exposure to ethanol to take the acid chloride to the ester) to the chloro-pyridine, 15. The halogen is then removed by catalytic reduction (16). The ester at the 4 position is converted to the desired functionality by successive conversion to the amide (17), dehydration to the nitrile (18), and finally addition of hydrogen sulfide. There is thus obtained ethionamide (19)... [Pg.255]

Cross coupling between an aryl halide and an activated alkyl halide, catalysed by the nickel system, is achieved by controlling the rate of addition of the alkyl halide to the reaction mixture. When the aryl halide is present in excess, it reacts preferentially with the Ni(o) intermediate whereas the Ni(l) intermediate reacts more rapidly with an activated alkyl halide. Thus continuous slow addition of the alkyl halide to the electrochemical cell already charged with the aryl halide ensures that the alkyl-aryl coupled compound becomes the major product. Activated alkyl halides include benzyl chloride, a-chloroketones, a-chloroesters and amides, a-chloro-nitriles and vinyl chlorides [202, 203, 204], Asymmetric induction during the coupling step occurs with over 90 % distereomeric excess from reactions with amides such as 62, derived from enantiomerically pure (-)-ephedrine, even when 62 is a mixture of diastereoisomcrs prepared from a racemic a-chloroacid. Metiha-nolysis of the amide product affords the chiral ester 63 and chiral ephedrine is recoverable [205]. [Pg.140]

Racemic 2-ethylhexanonitrile has been obtained only by the action of phosphorus pentachloride on 2-ethylhexanaldoxime 4 the levorotatory form has been prepared from the active amide by the method described.6 Other amides have been converted to nitriles by dehydration with thionyl chloride.6-6... [Pg.67]

The following arylacetamides have been prepared from the corresponding nitriles by the same method in the indicated yields 4 -methylphenylacetamide (70%), -isopropylphenylacet-amide (90%), 1-naphthylacetamide (54%), 5,6,7,8-tetrahydro-2-naphthylacetamide (90%), />-methoxyphenyl acetamide (76%), 3,4-dimethoxyphenylacetamide (82%), and 2,3-dimethoxyphenyl-acetamide (91%). Only in the cases of the alkoxy-substituted nitriles are the resulting amides soluble in the reaction mixture the other nitriles do not dissolve completely at any time during the reaction. [Pg.94]

Amides are the least reactive of the carboxylic acid derivatives, and undergo acid or base hydrolysis to produce the parent carboxylic acids, and reduction to appropriate amines (see Section 4.3.10). They can also be dehydrated to nitriles, most commonly with boiling acetic anhydride, (AcO)20, sulphonyl chloride (SOCI2) or phosphoms oxychloride (POCI3) (see Section 4.3.18). Amines (with one less carbon) are prepared from amides by the treatment of halides (Br2 or CI2) in aqueous NaOH or KOH. This reaction is known as Hofmann rearrangement (see Section 4.3.10). [Pg.101]

A variety of substituted 3-aminobenzo[6]thiophenes have been obtained by ring closure reactions of nitriles (equation 57). Various o -cyanophenylthioacetyl derivatives, when treated with base, yield the 3-amino derivatives (Section 3.15.2.2.3). The benzonitriles may be obtained by displacement of the o-nitro group from o -nitrobenzonitriles (74JOC3440). 2-Arylthio-l-chloroenamines are cyclized to 3 -dialkylaminobenzo[6]thiophenes in the presence of Lewis acid catalysts (equation 58). The 1 -chloroenamines may be prepared from t-amides or ynamines <8lH(15)l 179>. [Pg.925]

Other routes to 1,3-oxazines employ condensation reactions between /3-chloroketones and nitriles or between chloroalkyl amides and alkynes <69LA(723)ill) (Scheme 62). Thiazines are available through similar condensations between thioamides, aldehydes and acetylenes (74G849), and AH- 1,3-benzoxazines may be prepared from 2-hydroxybenzyl alcohols and nitriles in the presence of either perchloric or sulfuric acids (Schemes 63 and 64) (68MIP22700). [Pg.1019]

In addition to the procedures listed in Table 3.38, further reactions have been used to generate halides upon cleavage. In Section 3.5.2, iodolactonization is presented as a method for the preparation of iodomethyl lactones from resin-bound pentenoic or hexenoic acid derivatives. Closely related to the iodolactonization is the iodine-mediated formation of 2-(iodomethyl)tetrahydrofurans from resin-bound isoxazoli-dines (Entry 9, Table 3.38 for the mechanism, see Figure 15.5). Nitriles can also be prepared by cleavage and simultaneous dehydration of amides RCONH2 from the Rink or Sieber linkers with TFA anhydride (Entry 10, Table 3.38). [Pg.117]

Few preparations of nitriles have been performed on insoluble supports (Table 13.19). Aromatic and heteroaromatic nitriles have been prepared on solid phase from the corresponding iodoarenes by metallation followed by reaction with tosyl cyanide (Entry 1, Table 13.19). Moreover, the reaction of chloromethyl polystyrene with NaCN has been used to prepare support-bound benzyl cyanide (Entry 2, Table 13.19). Cleavage with simultaneous formation of nitriles can be achieved by treating polystyrene-bound sulfonylhydrazones with KCN (Entry 3, Table 13.19) or by cleaving amides from a Rink or Sieber linker with TFA anhydride (Entry 10, Table 3.38 [262]). Support-bound benzaldehydes have been converted into 3-aryl-2-propenenitriles by means of a Horner-Emmons reaction with (Et0)2P(0)CH2CN [263]. [Pg.358]


See other pages where Nitriles, preparation from amides is mentioned: [Pg.90]    [Pg.46]    [Pg.46]    [Pg.90]    [Pg.46]    [Pg.46]    [Pg.68]    [Pg.252]    [Pg.253]    [Pg.408]    [Pg.311]    [Pg.218]    [Pg.48]    [Pg.147]    [Pg.67]    [Pg.280]    [Pg.268]    [Pg.40]    [Pg.82]    [Pg.119]    [Pg.174]    [Pg.59]    [Pg.59]    [Pg.402]   
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See also in sourсe #XX -- [ Pg.13 , Pg.16 ]

See also in sourсe #XX -- [ Pg.4 , Pg.13 , Pg.95 ]

See also in sourсe #XX -- [ Pg.4 , Pg.13 , Pg.16 ]

See also in sourсe #XX -- [ Pg.13 ]

See also in sourсe #XX -- [ Pg.4 , Pg.13 , Pg.16 ]

See also in sourсe #XX -- [ Pg.4 , Pg.13 , Pg.16 , Pg.95 ]

See also in sourсe #XX -- [ Pg.13 , Pg.95 ]

See also in sourсe #XX -- [ Pg.13 ]

See also in sourсe #XX -- [ Pg.13 , Pg.95 ]




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