Selenoureas amines

There are amines such as A-methylnitroamine, that are too weakly nucleophilic to be able to form covalent adducts with arenediazonium ions. The products of the latter appear to be those of salts ArNJ N(N02)CH3, as found by Baranchik et al. (1957). Amides also appear not to be sufficiently nucleophilic, but thioamides are, as is shown by the reaction of A-phenylthiourea in the presence of NaOH (Scheme 13-12 Nesynov et al., 1970). First a (probably homolytic) phenylation-de-diazoniation takes place, followed by A-coupling. Selenourea also reacts a mixture of products is formed, which indicates a reaction of the same type as with thiourea (Nesynov and Aldokhina, 1976). 

Selenoureas are prepared by reaction of isoselenocyanates with amines, or by reaction of carbodiimides with a mixture of LiAlH4/Se and by reaction of cyanamides with LiAlH4/Se.267 272 The tyrosinase inhibitory activity and superoxide radical scavenger effect of selenoamides and selenoureas have been investigated (Scheme 84).273 275... 

The synthesis of 1,3-selenazoles from A -phenylimidoyl isoselenocyanates has been reported. N-phenylimidoyl isoselenocyanates 94 are prepared from N-phenylbenzamides 92. Treatment of 92 with thionyl chloride affords N-phenylbenzimidoyl chlorides 93, which yield imidoyl isoselenocyanates 94 on reaction with potassium isoselenocyanate. The imidoyl isoselenocyanates 94 were transformed into selenoureas 95 with either ammonia or primary or secondary amines. Reaction of 95 with an activated bromomethylene compound such as bromoacetophenone in the prescence of a base gave the 1,3-selenazole 97 via the salt 96 <00HCA1576>. 

A similar selenium insertion proceeds with lithium amides of secondary amines. In the presence of an isocyanide, lithium selenocarbamidates 2 are produced, which can be trapped with butyl iodide to give the corresponding iso-selenoureas 3 in good yields (Scheme 3) [5]. When the reaction is carried out under carbon monoxide atmosphere, the corresponding selenocarbamates are obtained [5]. 

The naphthoselenazole derivative (42 R = NHj) may be prepared by a Hantzsch-type synthesis from selenourea and 2-bromo-3,4-dihydronaphthalen-l(2 )-one-3-sulphonic acid followed by fusion of the product with sodium hydroxide. This amine (42 R = NHj) is ring-opened by sequential treatment with sodium borohydride and acetic anhydride to give compound (43), which may be cyclized to give the naphthoselenazole (42 R = Me). 

More exotic thioureas were the products of interesting reactions of isothiocyanates with ketimines, enamines imino-esters/ amidines, amidrazones, and substituted ammonium salts. Some selenoureas have been synthesized by the reaction of isoselenocyanates with amines, and the phosphorus compounds (300) were obtained analogously by treatment of w-mercaptoalkylphenylphosphines with phenyl isothiocyanate. The action of primary amines on (300) resulted in the formation of N-alkyl-lsT-phenylthioureas in high yields with simultaneous regeneration of the w-mercaptoalkylphenylphosphine. ... 

Examples of well-established 1,3,4-thiadiazole syntheses have been extended to the production and study of their selenium analogues." 1,4-Disubstituted selenosemicarbazides (191 R = Aik, Ar, or Ac) are readily accessible in good yield by the addition of isoselenocyanate esters (including benzoyl isoselenocyanate) to acylhydrazines." Their cyclization in acidic media affords the stable crystalline 1,3,4-selenadiazoles (192 R = Aik, Ar, or Ac) " the members of the aroylamino-series are stable to alkalis, but are hydrolysable by acids to the parent amines (192 R = H) these are convertible into conventional derivatives, as expected." Bis-selenoureas of type (194) are similarly accessible, but usually cyclize spontaneously to the substituted 2,5-dianilino-1,3,4-selenadiazoles (195). The action of acetic anhydride on (194) yields diacetyl derivatives of (195)... 

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