Molybdenum-catalysed

Barrett and Gibson also reported the application of the molybdenum catalysed cross-metathesis reaction to the elaboration of (3-lactams [31,32]. Protected allyloxy p-lactams 16 were successfully cross-metathesised with a selection of substituted styrenes to yield trans cross-metathesis products (Eq. 16). 

It is worth noting that the reactions with the unsubstituted styrene gave noticeably higher yields than the corresponding cross-metathesis reactions with the substituted styrenes. This appears to be quite a common characteristic of the molybdenum catalysed cross-metathesis reaction. 

Molybdenum-catalysed oxidation of alcohols by sodium percarbonate (Table 10.20)... 

Scheme 2.27 Enantioselective molybdenum-catalysed allylic alkylation of linear arylpropenyl carbonates (BSA = N, O-bis(trimethylsilyl)acetamide).

Scheme 2.28 Enantioselective molybdenum-catalysed allylic alkylation of branched phenylpropenyl carbonate.

Kaiser, N.F.K., Bremberg, U., Larhed, M., Moberg, C. and Hallberg, A., Fast, convenient, and efficient molybdenum-catalysed asymmetric allylic alkylation under noninert conditions an example of microwave-promoted fast chemistry Angew. Chem., Int. Ed. Engl., 2000,39, 3596-3598. 

In a related study Hallberg el al. also investigated molybdenum-catalysed allylic alkylations in solution and on solid phase33 demonstrating that microwave irradiation could also be applied to highly enantioselective reactions (Scheme 7.13). 

Scheme 7.13 Solid-phase molybdenum-catalysed allylic alkylation.

Most recently, Yoshihiro Yamamoto published a novel, outstanding one-pot synthesis of indigo from indole via a molybdenum-catalysed oxidation. [25] The... 

The pro-nucleophile (5-H -oxazol-4-ones) was first reported by Trost and coworkers as nucleophile for a molybdenum-catalysed allylation. The direct asymmetric aldol reaction of Masaki and coworkers has an atom economy of 69.8% (Scheme 23.4, due to the loss of HNEtj acetate salt during the acetylation) and an E-factor of 13.1. If the synthesis of catalyst is considered. 

Although molybdenum catalyses the reaction, its effect is much less pronounced than that of tungsten in small amounts, it hardly interferes. Moreover, the presence of molybdenum is revealed by the appearance of a yellow-brown color, which fades rapidly when Ti is added to 0.01 N HCl solution containing molybdenum. When molybdenum and phosphate are both present, a permanent dark red-brown appears on adding Ti to the acid solution. However, the reduction of malachite green hardly proceeds more rapidly than in the absence of phosphate. 

Two separate reports on the vanadium-catalysed epoxidation of allylic alcohols have appeared. In the case of secondary acyclic E -allylic alcohols opposite stereospecificity to peracid and molybdenum-catalysed systems is observed. This... 

An interesting study involving the controlled-potential oxidation of tetraphenylborate ion was carried out by Geske (271, 272) who showed how coulometric data can be used to elucidate the mechanisms of secondary reactions following the primary electrode process. Rechnitz and Laitinen (273) also used controlled-potential coulometry to confirm the mechanism of the molybdenum-catalysed reduction of perchlorate ion. An attempt by Kennedy (274) to study the kinetics of the reduction of phosphotimgstic acids was unsuccessful owing to interference by secondary reactions. 

---