Pseudourea

Addition of alcohols and phenols ia the presence of anhydrous hydrogen chloride gives 0-substituted pseudourea salts (17). The reaction is sluggish except with the lower alcohols, and long reaction time and temperatures up to 100°C are requited to obtain good yields. 

Pseudo-homsaure, /. pseudouric acid, -hsm-stoff, in. pseudourea. -katalysator, m. pseudocatalyst. -katalyse, /. pseudocatalysis. 

Etbylaminoetbyl-pseudourea, mw 131.17 Refs 1) Beil, not found 2) CA, not found 2-EthyI- (2-nitram inoethyI) 3-nitropseudourea, NH... 

Ref 2,4). More recently, ethylene diamine was reacted with 2-methyI-l-nitro-2-thio-pseudourea (also a prepn for ethylenegnani-dine without the nitro)(Ref 8). Treatment with sulfuric or perchloric acids converts this compound to the nitric acid salt of 2- amino-imidazole, mp 112-13°(Ref 7)... 

E. Reaction of Various Reagents with Pseudoureas to Give Substituted Pseudoureas. 180... 

In 1894 the first oxygen ether of a urea, a pseudourea, was quantitatively prepared by the reaction of ethanol with diphenylcarbodiimide at 180°C in a sealed tube [1] (Eq. 1). Shortly thereafter it was shown that sodium ethylate... 

Recently cyanates have been also shown to react with amines to give pseudoureas [13]. 

The best methods for preparing pseudoureas are based on these earlier methods they are summarized in Eqs. (7)—(13). 

Pseudoureas undergo some of the additional reactions [14,16, 26] shown in Scheme 1. 

Some of the commercial uses that pseudoureas have found are herbicides [27, 28] inhibitors for discoloration of color photographic layers [29] monomers for the preparation of some novel copolymers [30, 31] and dyes [32,33]. A survey of the recent decennial indexes of Chemical Abstracts should be made to see the large number of pseudoureas reported for varied uses. Pseudothioureas have also been found useful as radiation protective agents [34]. 

To date no general review of pseudoureas or pseudothioureas has appeared, but there is a recent review [14] which is limited to 0,N,N -trisubstituted pseudoureas. 

This pseudourea reacts with oxalic acid and mercuric chloride to give addition compounds useful for identification purposes. 

Cyanamide and substituted cyanamides react with alcohols to give pseudoureas. Cyanamide reacts with alcohols in the presence of anhydrous hydrogen chloride, whereas disubstituted cyanamides require slightly more than an equivalent of sodium alkoxide for reaction with the alcohol. (See Tables III and IV.) Catalytic amounts of sodium alkoxides are sufficient to induce the reaction of a cyanamide with primary, secondary, or tertiary alcohols [21] (Eq. 17). When both R groups are secondary alkyl groups, alkaline catalysts... 

This procedure is essentially the same for the other pseudoureas shown in Table III using either 1.1 or 0.1 equivalent of sodium alkoxide. 

Preparation of Pseudoureas by the Reaction of Cyanamides with Alcohols< in the Presence of Anhydrous Hydrogen Chloride [2,4]... 

Werner [10] suggested that, on heating, urea tautomerizes to the pseudourea structure which, on reaction with methyl sulfate, allows the isolation of 2-methylpseudourea (Eq. 22). The product was difficult to crystallize and it was isolated as the picric acid derivative. 

Recently Piasek and Urbanski [47] gave further proof of the pseudourea structure of urea by showing that diazomethane reacts at room temperature with urea dissolved in methanol or ethanol to give 2-methyl- or 2-ethylpseudo-urea, respectively, in 11-12% yield. 

The active hydrogens of pseudoureas react with various reagents, such as sodium hypochlorite [72], acyl halides [73], sulfonyl halides [19], isocyanates [26], isothiocyanates [26, 74] cyanamide, [75] and esters [76], to give linear or cyclic derivatives as shown in Scheme 2. 

Transalkylation of Pseudourea Preparation 2-Cyclohexyl-3,3-di-n-butyl-pseudourea [21]... 

Werner [10] later found that urea reacts with methyl sulfate to give 2-methyl-pseudourea, but the isolation of the product from the syrup is difficult and is usually done via the picrate. The reaction is usually carried out at about 40°C (7 hr) because at temperatures above 100°C the reaction is too violent [11] (Eq. 5). 

Chemical Abstracts uses the name pseudourea rather than isourea, which was widely used in the older literature. The numbering of substituents is shown in (I). An analogous system is used with pseudothioureas. 

Before the synthesis of the pseudoureas was published, Bernthsen and Klinger [6] reported a pseudothiourea synthesis involving the reaction of thioureas with alkyl halides. This reaction was briefly reviewed by Dains [16] and Stieglitz [49, 50], and it found many commercial applications [51-53]. The preparation of isothiouronium salts by the direct action of thiourea and halogen acids on alcohols (primary, secondary, and tertiary) was reported by Stevens [8] and further developed by Johnson and Sprague [54, 55] (Eq. 25). 

Transalkylation of the 2-Methyl or 2-Ethyl Group of a Trisubstituted Pseudourea with 0.1 Equivalent of Sodium Alkoxide... 

Reaction of Ar-(4-chlorophenylimino)chloroformic acid 2,4-dichloro-phenyl ester with dialkylamines at room temperature in benzene solution to give Ar-(4-chlorophenyl)-2-(2,4-dichlorophenyl)-1,3-dimethylpseudourea. Other pseudoureas were prepared similarly [27, 77]. 

Reaction of cyanates with primary and secondary amines to give 2-substituted pseudoureas [13]. 

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