Mannich bases, hydrogenolysis

By-products can be formed in the synthesis of phosphines 263 with the iodome-thylatcs of ferroccnyl Mannich bases, as they tend also to give phosphonium salts 267 in amounts that depend on the duration of the reactionFurthermore, in the reaction with arsines, due to the reducing properties of such reagents, hydrogenolysis of the CH2—N bond may occur with the formation of a propiophenone derivative instead of the expected product 263 (X = As). 

Reducing agents have two main effects on Mannich bases, namely, hydrogenolysis of a bonds and reduction of unsaturated functional groups. 

The hydrogenolysis product of the Mannich base is also obtained through the formation of a suitable intermediate, in some cases not isolated or purified, which is subsequently subjected to hydrogenation. This may be an unsaturated derivative (R=CH2) produced by deamination of Mannich base, - - or the R—CH2—X (X = 0-Acyl or S-Alkyl -) product deriving from amino group replacement. 

Debenzylation of a Mannich base by hydrogenolysis is widely adopted. - It has been used, for example, in the synthesis - of aminomethylphosphonic acid (H0)2P0—CH2NH2. 

In the hydrogenolysis of acetylenic Mannich bases, rearrangement with double bond migration, accompanying the elimination of the amine, may take place with formation of an alicne derivative instead of the expected methyl alkyne. 

A typical example of hydrogenolysis is given by the synthesis of 2,4-dimethyl estradiol 465, obtained in gO(xl yield from the dimcthylamino Mannich base of the corresponding 2-mcthyl derivative. ... 

The CHj group can be similarly introduced into compounds of the same type by direct hydrogenolysis of the Mannich base (Fig. 108, Chap. II). 

The functionalization of porphyrins is performed by introducing a methyl group into dicyanocobaltheptamethylcorrin through hydrogenolysis of the corresponding ami-nomethyl derivative (Ref. 176 for Chaps. I and II). An appreciable number of replacement reactions on the amino group of etioporphyrin Mannich bases has also been tried (Ref. 832 for Chaps. I and II). 

Replacement of hydrogen by methyl via tert. amines Hydrogenolysis of Mannich bases... 

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