1.1- Enediamines from amines

As we have mentioned above, ketene N9S- and N,0-acetals are the intermediates in the preparation of 1,1-enediamines from ketene dithioacetals and ketene acetals, respectively, and they can be isolated from the reactions5,51,52,72. Further substitution of the methylthio or the alkoxy groups by amines yields 1,1-enediamines. 

The reaction of amines and ketene acetals was used as a main synthetic approach to 1,1-enediamines in earlier years72. Both simple and conjugated 1,1-enediamines can be obtained by this route. Displacement reaction of ketene acetal 34 with two equivalents of piperidine furnishes 1,1-dipiperidinoethene (35) in 62% yield (equation 9)73. Primary amines and ammonia react with 34 to give amidine derivatives. Cyano-74 and trifluor-oacetyl-substituted enediamines75 have been synthesized from the corresponding ketene acetals in good to excellent yields (e.g. equation 10). 

Ketene N, O-acetals are converted to 1,1-enediamines when reacted with amines. For example, compound 45 has been prepared by substitution of the methoxy with amine (equation 16)79. Symmetric 1,1-enediamines are obtained when both the alkoxy and the amino substituents are displaced by the amine employed81. In this way, the reaction between ketene N, O-acetals 50 and piperidine leads to 1,1-dipipefidinoethylene (35) (equation 17)81. Alternatively, 35 can be prepared from the reaction of piperidine with triethyl orthoacetate82,83 or with ethoxyacetylene84, reactions which probably proceed via a ketene TV, 0-acetal intermediate. 

Condensation reaction between active methyl and methylene compounds and S-alkylated thioureas provides another useful synthetic pathway to the 1,1-enediamines. Rajappa and coworkers20 reported that nitromethane condensed with S-methylated thioureas 72, prepared from the reaction of amines and methyl isothiocyanate followed by S-methylation, to form asymmetric nitro 1,1-enediamines 73 (Scheme 5). 

A few asymmetric 1,1-enediamines, i.e. with different a-amino substituents, have been prepared from ketene iV.S -acetals and amines For example, the primary 1,1-enediamines 45 are obtained by treating ketene 7V,5-acetals 44 with ammonia... 

Similarly, urea A, 0-acctal 64 undergoes condensation reaction with weak carbon acids to afford acyclic 1,1-enediamines with the elimination of alcohol and amine , A number of active methyl compounds such as an aliphatic ketone, acetophenone, imino ester and thioacetoamide has been successfully converted to 1,1-enediamines. Lactones, lactams and thiolactams condense with 64 to give enediamines 65 in moderate yields (equation 24). Very weakly activated methyl groups are also reactive towards urea A(,<9-acetal 64, and 1,1-enediamines 66-71 are prepared from the corresponding re-actants ". ... 

Reduction of dinitrotoluenes is carried out industrially with Raney-nickel or palla-dium/carbon catalysts, under a hydrogen pressure of 70 bar and at a temperature of up to 150 °C, in a cascade or loop reactor. The concentration of dinitrotoluene in the reaction mixture is kept very low to achieve yields of over 99%. The reaction mixture is divided into a recycle stream and a residue, from which the catalyst is separated in a filter or cyclone. Distillation of the reaction product then yields the components methanol, water, diamines and a residue. Distillation of the water-free amines is carried out under vacuum (approx. 50 mbar), with 2,3- and 3,4-tolu-enediamine being separated in a fronts column. A tar-like residue is removed as a bottom product in the main column, while a mixture containing 2,4- and 2,6-tolu-enediamine is collected as an overhead fraction. 

Apart from proteins and amino acids, there are other nitrogenous compounds in the latex. These compounds are mainly amines and the corresponding derivatives, such as choline, methylamine, tetramethylenediamine, pentamethyl-enediamine, ethanolamine and trigonelline. These amine compounds, such as choline, a quaternary saturated amine, have been reported to be an accelerator, and antioxidant for the raw rubber. ... 

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