Tetrakis titanium, reactions with amides

In 1966, Weingarten and White93 reported a simple route to simple 1,1-enediamines. Under mild conditions, aliphatic amides underwent reaction with tetrakis(dimethylami-no)titanium (60) to afford 1,1-enediamines 61. The reaction could be carried out with most of the common acid derivatives such as free acid, ester and anhydride via the amide (equation 22). A probable mechanism involving intramolecular dehydration has been proposed in Scheme 442. 

Tetrakis(dimethylamino)titanium converts DMF to tris(dimethylamino)methane (529 equation 236). This compound is also formed in the reaction of V-tetramethyloxamide with the titanium reagent, whereas amides which have a-CH bonds are converted to ketene aminals. Cyclic and spitocyclic compounds, containing the substitution pattern of a trisamino compound, are formed in the reaction of IVA -dialkylformamides or A/ -aryl-(VJV-dialkylformamidines with aryl isocyanates. Similar compounds, e.g. (530 equation 237), are produced in the reaction of imidazolines or lactamid-ines with isocyanates. 

D. Reaction of Aliphatic Amides with Tetrakis(dimethylamino)titanium. . 1318... 

A stereochemical control of the Ugi reaction can be effected with carbohydrates as chiral templates (e.g. tetrakis(O-pivaloyl)galactosylamine), which gives rise to easily separable amides. From these a variety of non-natural amino acids can be derived after acidic hydrolysis. The Passerini reaction, related to the Ugi rearrangement, gives a-hydroxyamides. A modification of this reaction using titanium tetrachloride gives a-branched amides in high yields via C-metalated imidoyl chlorides (equation 38). 

Group 4 (IV B) dithiocarbamate chemistry is constrained to the 4-4 oxidation state. The first reported example was the eight-coordinate tetrakis(dithiocarba-mate) titanium complex, [Ti(S2CNBz2)4], prepared by Dermer and Femelius in 1934 (608), while the heavier zirconium and hafnium analogues were first prepared by Bradley and Gitlitz (193) from the reaction of metal amides, [M(NR2)4] (M = Ti, Zr, Hf), with carbon disulfide. 

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