Tungsten complexes amides

Tungsten complexes, 3, 973-1015 alkoxy carbonyl reactions, 2, 355 alkyl alkoxy reactions, 2, 358 amides... 

The aminocarbonylation of alkynes has been less explored as compared to that of alkenyl and (hetero)aryl halides. Nevertheless, several noteworthy applications of this reaction have been reported, including the syntheses of 2-ynamides, chiral 2-carbamoyl-7r-allylic tungsten complexes, angular triquinanes, 2-(carbamoylmethylene)tetrahydrofurans, alle-nyl amides, and others. ... 

Introduction.—Reviews on the molecular structure of co-ordination compounds and organometallic compounds containing molybdenum and tungsten as determined by X-Tdiy diffraction have appeared. Structural aspects of Mo , Mo, and Mo complexes have been examined and molybdenum complexes themselves have also been specifically reviewed. A discussion of molybdenum and tungsten dialkyl-amides and disilylamides has been included in a recent review and the co-ordination chemistry of aryldiazonium cations (ArNj) of molybdenum and tungsten has been discussed. ... 

Tungsten aryloxo complexes have been shown to catalyze the intramolecular metathesis reactions of di- and tri-substituted co-unsaturated glucose and glucosamine derivatives to yield bicyclic carbohydrate-based compounds containing 12- and 14-membered rings [108,214,215]. An example is shown in Eq. 37. The tolerance for amides and esters is noteworthy, as are the yields and the size of the rings that are formed. 

Although the structure of the complex arising from I52/CH2CI2 is not clear, this catalyst is excellent in terms of ease of preparation. The catalyst is very active for formation of cycloalkynes with ring sizes different from those of diynes (Table 6.5). In contrast to tungsten alkylidyne complex 150, catalyst 152/ CH2CI2 is sensitive toward an acidic proton such as amide proton and exhibited remarkable tolerance towards many polar functional groups (Table 6.5). 

The metathesis of symmetrical aliphatic carbodiimides is also catalyzed by tungsten imido complexes above 140 Other carbodiimide metathesis catalysts include Cr(ll)/Si02/ iminophosphoranes, imido circonocenes, guanidine supported titanium complexes and group 14 amide complexes. ... 

Treatment of the complexes NMe4[Cr(CO)5) =C(0)Me ] with iodine in the presence of base and alcohols affords carboxylic acid esters in reasonable yield. Use of water or an amine in place of the alcohol provides the carboxylic acid or the amide. The molybdenum and tungsten derivatives... 

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