Amido-derivatives

The fact that pyromeconic acid and allomaltol were only available with difficulty meant that direct synthesis of certain 3-hydroxy-4-pyridinones was not possible. However the demonstration that some of these compounds were accessible from maltol or ethylmaltol by functionalizing the position adjacent to the ring-oxygen by an aldol condensation and N-oxide intermediates led to the preparation of 2-(l -hydroxyalkyl) and 2-amido derivatives with usefully high affinities for Fe + (70). 

Methyl 6-amino-6-deoxy-a-D-glucopyranoside derivatives 2c were synthesized in our laboratory by a somewhat different procedure [31]. 6-0-Sulfonyl or 6-bromo-6-deoxy derivatives of methyl a-o-glucopyranoside were substituted at C-6 by sodium azide. The 6-azido-6-deoxy intermediate was then treated by acyl chlorides in the presence of triphenylphosphine (Staudinger reaction) to afford amido derivatives which were finally de-O-acetylated to give 2c. The same reaction pathway allowed the preparation of 6-alkylamido-6-deoxy-D-glucopy-ranose derivatives, starting from o-glucose [31]. 

R(H)N—N ], and diazenido (R—N=N ) [68, 71, 72] ligands have been isolated and characterized. Among them, the amido/imido complexes are related by a reduction step. Also, cleavage of the N=N bond of diazene or isodiazene/hydrazido(2—) ligands, to produce imido or amido derivatives, requires several Fl+/e transfer steps. 

In earlier sections it has been shown that the reaction of a magnesium dialkyl with one equivalent of a primary amine usually affords the primary amido derivative. However, it is also possible to effect elimination of the second equivalent of alkane to give magnesium imides. The reaction of MgEt2 with aniline in thf proceeded via an amido intermediate which eliminated ethane to yield the hexameric imido compound [ (thflMgNPhJg] which was the first homometallic magnesium imide to be structurally characterized. Equation (3.9). 

It will be immediately apparent from Tables 6.1 and 6.2 that amides of the groups 4-6 elements are by far the most numerous. Furthermore, the number of second and third row element amido derivatives of these groups approaches or exceeds those of the first row. It can also be seen that for the first row elements homoleptic amides in the highest oxidation... 

Other interesting anionic transition metal amido derivatives have come from the reactions of primary amido ligands with metal halides by Fenske and coworkers. This has allowed the synthesis of a range of cobalt, nickel and copper amido cluster species with unusual structures which also incorporate NPh as coligand (cf. Table... 

In a similar vein, it was shown that molybdenum amido derivatives of the isolobal terminal phosphide and carbide, " and related chalcogenide atoms,could be obtained. Detailed mechanistic studies of the Mo N(R)Ar 3/N2 system involving X-ray, EXAFS, magnetic, Raman, and isotopicaUy labelled NMR spectroscopy showed that the reaction proceeded through an intermediate involving an end-on bound N2 bridging the molybdenum centres (Scheme... 

Numerous studies involving similar amido derivatives of metals such as Ti (e.g. heterometallic cross-coupling of benzonitrile with carbon dioxide, pyridine, and benzophenone with mixed [Ti N(Bu )Ar 3] and [Mo N(Bu )Ar 3] systems), V (e.g. denitrogenation of a vanadium nitride by carbon disulfide and dioxide), Nb (e.g. the... 

In the 1980 edition of this chapter, the total number of amido derivatives of all types for the group 12 metals was less than 200 characterized compounds. These were described in ca. 90 papers in the primary literature. Detailed structural knowledge of these compounds was... 

Four-coordinate, monomeric aluminium amides. Monomeric, four-coordinate aluminium amido derivatives are now quite numerous, yet none had been structurally characterized before 1980. They may be divided into two broad categories those which are Lewis base adducts and those in which four-coordination for aluminium is a result of complexation by a chelating ligand. 

Mixed aluminium-transition metals amido derivatives are also known. The reaction of AlMe3 with [Mn N(SiMe3)2)2(thf)] afforded [(Mn(p-Me) N(SiMe3)2AlMe3 )2], which comprises manganese centered units dimerized via Mn(p-Me)2Mn interactions with... 

Upon acetylation and subsequent O-deacetylation in alkaline media, both the mono- and bis-(amido) derivatives of mono- and disaccharides always showed great stability, with high recoveries of the original amido sugar. 

The presence of alkoxide ion would enhance the rate of ammonolysis, and the formation of bis(amido) derivatives by an ortho-ester mechanism (see Section VI, p. 110) would be partially suppressed in the competitive set of reactions. Thus, ammonolysis of penta-O-benzoyl-D-glucose in the presence of 5 mmolar proportions of sodium meth-oxide showed a decrease of 11% in the yield of the bis(benzamido)-glucitol derivative as compared with the same reaction conducted without added methoxide ion.47... 

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