Molybdenum amides

Tsai Y-C, Cummins CC. Base-catalyzed dinitrogen cleavage by molybdenum amides. Inorg Chim Acta. 2003 345 63-69. 

Tsai Y-C, Johnson MJA, Mindiola DJ, Cummins CC, Klooster WT, Koetzle TF. A cyclometalated resting state for a reactive molybdenum amide favorable consequences of p-hydrogen elimination including reductive cleavage, coupling, and com-plexation. J Am Chem Soc. 1999 121 10426-10427. 

Ketones and carboxylic esters can be a hydroxylated by treatment of their enolate forms (prepared by adding the ketone or ester to LDA) with a molybdenum peroxide reagent (MoOs-pyridine-HMPA) in THF-hexane at -70°C. The enolate forms of amides and estersand the enamine derivatives of ketones can similarly be converted to their a hydroxy derivatives by reaction with molecular oxygen. The M0O5 method can also be applied to certain nitriles. Ketones have also been Qc hydroxylated by treating the corresponding silyl enol ethers with /n-chloroperoxy-... 

The ruthenium carbene catalysts 1 developed by Grubbs are distinguished by an exceptional tolerance towards polar functional groups [3]. Although generalizations are difficult and further experimental data are necessary in order to obtain a fully comprehensive picture, some trends may be deduced from the literature reports. Thus, many examples indicate that ethers, silyl ethers, acetals, esters, amides, carbamates, sulfonamides, silanes and various heterocyclic entities do not disturb. Moreover, ketones and even aldehyde functions are compatible, in contrast to reactions catalyzed by the molybdenum alkylidene complex 24 which is known to react with these groups under certain conditions [26]. Even unprotected alcohols and free carboxylic acids seem to be tolerated by 1. It should also be emphasized that the sensitivity of 1 toward the substitution pattern of alkenes outlined above usually leaves pre-existing di-, tri- and tetrasubstituted double bonds in the substrates unaffected. A nice example that illustrates many of these features is the clean dimerization of FK-506 45 to compound 46 reported by Schreiber et al. (Scheme 12) [27]. 

The total syntheses of these pepper alkaloids are not those of pyrrolidines but rather syntheses of their acid parts. Thus dihydrowisanidine (137) has been prepared by a series of reactions, the key step of which is the formation of the carbon-carbon double bond by a Wittig-Homer reaction (217, 218). Schemes 41 and 42 summarize two syntheses of okolasine from sesamolmethyl ether (279) of course, routes to okolasine also yield the corresponding piperidine alkaloid wisanine. Molybdenum-catalyzed elimination of allylic acetate (149) yielded (E,E)-diene ester 150 en route to trichonine (220) worthy of note is the use of an aluminum amide in the preparation of amide 143 from ester 150 (Scheme 43). 

Following resolution with (—)-quinine, (+)-465 was transformed into the (-l->2-formamido derivative which was condensed with the acid chloride of (+)-465 to give the secondary amide 468. From this point, the cyclic imidate salt 469 was prepared, but cyclization to the dodecahedrane nucleus could not be realired With Thiele s add as starting material, several routes to triquinacene and 2,3-dihydrotriquinacen-2-one 462) have been developed Triquinacene reacts with Mo(CO)g to give tricarbonyl(triquinacene)molybdenum (470) and with (CHjCI -... 

An important recent development in the area of the monodentate amido metal chemistry has come from the group of Cummins who introduced ligands of the type —N(R)Ar (for example, R = Bu , 1-adamantyl (I-Ad), 2-adamantyl (2-Ad), —C(CD3)2(CH3) Ar = Ph, C6H3Me2-3,5, C6H4F-4).These allowed the isolation of an Mo N(R)Ar 3 species having three-coordinate molybdenum as well as three-coordinate derivatives of several other metals. Apart from [M N(SiMe3)2 3] (M = Y," La), the molybdenum compounds are the only examples of structurally characterized open shell, three-coordinate homoleptic amides... 

Oxodi peroxymolyhdenum(hexamethy1phosphori c tri amide) Molybdenum, (hexamethylphosphoric tr1am1de)oxod1peroxy- (8) Molybdenum,... 

In the same way, dipyridyl amide-functionalized supports suitable for the SPE of metal ions from aqueous solutions can be prepared. The resins are synthesized via the copolymerization of the functional monomer endo-norbornene-5-yl-N,N-di-2-pyridyl carboxylic amide with a molybdenum-based catalyst (42). Essentially no loss of performance was observed after extensive use over more than twenty cycles. After exposure to air for at least 2 months, a change in color from bright white to yellow was observed. However, this change in color did not influence the characteristic properties of the resins. 

Monomeric non-oxo molybdenum(V) complexes have been isolated with nitride (N3 ), imide (NR2-) and amide (NRR -) ligands, which may act as models for intermediates in the degradation of dinitrogen in nitrogenase. However, no molybdenum(V) compounds are yet known which correspond to the diazenide or hydrazide analogues of the molybdenum(IV) complexes described in Section 36.4.2.3. 

In liquid NH, solution, potassium amide reacts with MoO to form the sail K3M0O1N. completely hydrolyzed by H.O. in which the molybdenum atom is Ihe center of a monomeric tetrahedral anion, being surrounded by three oxygen and one nitrogen atoms. 

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