Amide, sodium dehydration

On heating, an alkanolamine soap first dehydrates to the amide this is also obtained from the methyl ester of the fatty acid by heating with the alkanolamine at 60°C in the presence of a catalytic amount of sodium methoxide. Methanol is removed under partial vacuum. At higher temperature, the amide is dehydrated to an oxa2oline. 

Sodium acetate anhydrous Sodium amide Sodium oxide Trimethyl borate dehydrating agent, air conditioning Silica gel... 

Nudiflorine (5-cyano-I-methyl-2-pyridone) (XII-S26), an isomer of ricinidine (demethoxyricinine), has been isolated from the leaves of TYewia nudiflora Linn. It has been synthesized from 5-carbomethoxy-2-pyrone by treatment with ammonia to form 6-oxonicotinic acid, which is alkylated via its sodium salt to the A-methyl derivative. Esterification, followed by conversion to the amide and dehydration, gives nudiflorine. It has been suggested that both ricinidine and... 

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 ... 

A series of N-substituted narceine amides (Section III,D,1) was prepared from 101 under the action of primary amines (100). Acid-catalyzed dehydration transformed these amides to corresponding imides (ene lactams) of the ( )-narceine imide (117) type (100). Similar transformations were performed in the hydrastine series (101). JV-Methylhydrastine (98) when treated with dilute ammonium hydroxide gave hydroxy lactam 127, which was dehydrated to (Z)-fumaridine (113) (5). Sodium borohydride was able to reduce the stilbene double bond in 98 to produce saturated lactone 132 (5). 

Sodium amide is a dehydrating agent. It is used in preparing sodium cyanide and hydrazine, and in many organic synthetic reactions such as Claisen condensations, alkylations of ketones and nitriles, and in ammonoly-sis reactions. 

It is well documented that the isoimide is the kinetically favoured product and that isomerization yields the thermodynamically stable imide when sodium acetate is used as the catalyst. High catalyst concentrations provide maleimides with low isoimide impurity. The mechanism by which the chemical imidization is thought to occur is shown in Fig. 3. The first step in the dehydration reaction may be formation of the acetic acid-maleamic acid mixed anhydride. This species could lose acetic acid in one of the two ways. Path A involves participation by the neighboring amide carbonyl oxygen to eject acetate ion with simultaneous or subsequent loss of proton on nitrogen to form the isoimide. Path B involves loss of acetate ion assisted by the attack of nitrogen with simultaneous or subsequent loss of the proton on nitrogen to form the imide. If the cyclodehydration is run in acetic anhydride in the absence of the base catalyst, isoimide is the main reaction product. 

The 3-benzyloxyisoxazole system has functioned as a storable /3-keto amide unit in the construction of tetracyclines (78JA3609). Michael addition of the anion of the 3-benzyloxyisoxazole (442) to the dienolone (441) followed by deesterification-decarboxylation gave rise to (443) in 80% yield. Dehydration of this material and sodium hydride-induced cyclization afforded (445). Hydrogenolysis over palladium on carbon produced the desired ( )-dedimethylamino-12a-deoxyanhydrotetracycline (446 Scheme 99). This isoxazole route has also been extended to the preparation of a tetracycline having the usual amino function in the A ring. 

In preparation for the eventual removal of the undesired oxygen function at C-10 of 313 via a Birch reduction, the phenol 313 was phosphorylated with diethyl phosphorochloridate in the presence of triethylamine to give 314, which underwent stereoselective reduction with sodium borohydride with concomitant N-deacylation to deliver the amino alcohol 315. N-Methylation of 315 by the Eschweiler-Clarke protocol using formaldehyde and formic acid followed by ammonolysis of the ester group and acetylation of the C-2 hydroxyl function afforded 316. Dehydration of the amide moiety in 316 with phosphorus oxychloride and subsequent reaction of the resulting amino nitrile 317 with LiAlH4 furnished 318, which underwent reduction with sodium in liquid ammonia to provide unnatural (+)-galanthamine. 

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). 

Aromatic nitriles are also prepared by heating amides with phosphorus pentoxide, phosphorus oxychloride, phosphorus pentachloride, thionyl chloride, and ammonium sulfamate. In addition, the action of a double salt of aluminum and sodium chlorides, NaCl- AlClj, gives excellent yields of nitriles from both aliphatic and aromatic amides. Heating an amide with phthalic anhydride causes dehydration. A novel synthesis consists in treating a mixture of an aromatic acid and p-toluene-sulfonamide with phosphorus pentachloride the yields of nitriles range from 63% to 79%. ... 

Sodium cyanoborohydride (10) produces mainly 1,4-dihydropyridines (11) in the reduction of 3,5-di-cyano- and 3,5-diethoxycarbonyl-pyridines, diborane produces more of the 1,2-isomer. With NBH, mixtures of 1,2- and 1,4-dihydro adducts are produced, the latter predominating when carried out in pyridine solution. Nicotinamide (13) in ethanol can be reduced to (8) in moderate yield at 140 C in diglyme the tetrahydropyridine (8) was isolated in admixture with the piperidine (14), presumably via dehydration of the amide. 3-Nitropyridine affords 3-nitropiperidine in moderate yield when reduced in ethanol. The carboxylic acid and halo derivatives of pyridine are generally not reactive toward NBH. 

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