Imino ester

Amidines are best made in two stages a nitrile reacts with dry HCl and anhydrous alcohols to give an imidic ester (imino-ether) which yields an amidine with NH3. 

Acyl carbonates (234), alkoxyquinones (235) as vinylogous esters, imino ethers (236), and diketene (237) react with ethyleneimine to give the corresponding acylated ethyleneimines. 

The addition of dry HCl to a mixture of a nitrile and an alcohol in the absence of water leads to the hydrochloride salt of an imino ester (imino esters are also called imidates and imino ethers). This reaction is called the Pinner synthesisThe salt can be converted to the free imino ester by treatment with a weak base such as sodium bicarbonate, or it can be hydrolyzed with water and an acid catalyst to the corresponding carboxylic ester. If the latter is desired, water may be present from the beginning, in which case aqueous HCl can be used and the need for gaseous HCl is eliminated. Imino esters can also be prepared from nitriles with basic catalysts. ... 

Mercaptoalkylamines (353) give Az-thiazolines (354) on reaction with esters, imino esters or thioesters. This method has been particularly successful with cysteine and its derivatives (Scheme 224) (16B1110). 

Note The addition of alcohols to pyrazinecarbonitriles gives pyrazinecarbox-imidic esters ( imino esters ) these undergo facile hydrolysis864 1068 1127 1256 to regular esters and/or amides. 

IMINO ESTERS (IMINO ETHERS) AND AMIDINES TABLE 77. AMIDINES... 

Imino esters—Continued preparation, 483, 634 preparations listed in table 76, 637 pyrolysis to amides, 376 Imino ethers, see Imino esters Imino ketones, preparation, 730 jS-Iminonitriles, hydrolysis, 351 preparation, 730 Indoles, alkylation, 836... 

If we put two of these functions on the same carbon, in principle, one may be able to produce a maximum of two C-C bonds in reactions with appropriate carbon nucleophiles. Which functions are these Acetals, thioacetals, aminals, a-dihalidcs, and so on. Then, all of them should be FN = 2 groups. This analogy continues with triheterosubstituted (FN = 3) and tetraheterosubstituted (FN = 4) carbon functions. Unsaturated systems are also classifiable in these terms. Every one knows that a ketone can yield two C-C bonds. This circumstance evolves into the realization that the tt and the a bonds of C=X both serve their individual purpose as potential precursors of C-C bonding. This allows the inclusion of imines, thioketones, and diazocompounds as functions capable of forming a maximum of two (FN = 2) C-C bonds. Similarly, esters, imino- and thioesters, and acyl halides display central carbons with FN = 3, while carbonates, carbamates, ureas, and carbon dioxide are all FN = 4 groupings. 

Pseudo PoIy(Amino Acids) Composed of Amino Acids Linked by Nonamide Bonds such as Esters, Imino Carbonates, and Carbonates... 

Th Conversion of Ketones to Imido Esters. Imino esters may be pr pared by the reaction of hydrazoic add with ketones in the presence of alcohol. - ... 

Examples of cyclic units are 1,4-phenylene, 2,6-naphthalene and fr s-1,4-cyclohexylene rings. The linking group connects the cyclic units on each side to give the chain a linear character. The preferred confirmation is planar (linear). A number of different groups fulfil these requirements direct bond, ester, imino, azo, azoxy, and methylol groups (semiflexible). 

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