Tungsten carbonyl olefination

Similarly, neither zirconium, tantalum, molybdenum, nor tungsten carbene complexes have been applied extensively by organic chemists for carbonyl olefination [609,727-729], probably because of the difficulty of their preparation and the high price of some of these compounds. These reagents can, however, have appealing chemo- and stereo-selectivity (Table 3.11). 

Another example of a stoichiometric carbonyl-olefination reaction facilitated by a reagent which may be assumed to generate an intermediate tungsten carbene complex is shown in eqns. (7) and (8). The ketone can be added as soon as methane evolution has subsided (Kaufftnann 1986). 

Carbonyl Olefination Using Zirconium, Tantalum, Niobium, Molybdenum, and Tungsten Carbene Complexes... 

Besides the carbene complexes, the tungsten alkyUdynes 62 [135] are also employed for carbonyl olefination. The complexes 62 react with carbonyl compounds to give 0x0 vinyl complexes 63, which are hydrolyzed with 1 N NaOH to form the... 

Tab. 4.20. Carbonyl olefination with tungsten alkylidene complexes 60 and 61.

The M(C0)6 (M = Cr, Mo, W) stable carbonyls have been used to prepare metal supported catalysts of elements of group 6 that have been used as catalysts in several reactions, such as metathesis, water-gas shift, CO hydrogenation and olefin hydrogenation and polymerization [15-24]. Table 8.2 compiles several examples in which M(CO)s (M = Cr, Mo, W) compounds are used as an alternative for preparing chromium-molybdenum or tungsten-based catalysts. 

Both homogeneous and heterogeneous catalysts can be used in olefin metathesis.6 26 28 29 31 In general, tungsten or molybdenum halides or carbonyl complexes... 

In organic chemistry one surely thinks at once of the construction of cyclopropane derivatives from olefins and carbenes. Indeed, it has been shown that this also is possible with our complexes and with C=C double bonds that are electron-poor and arc either polarized or easily polarizable (77-81). As an example of this, I would like to cite the reaction of penta-carbonyl[methoxy (phenyl) carbene]chromium (0), -molybdenum (0), or -tungsten(0) with ethyl vinyl ether (79). One obtains the corresponding cyclopropane derivatives in this case, however, only when one removes... 

Fujiwara, Y., Ishikawa, R., Akiyama, F., Teranishi, S. Reductive coupling of carbonyl compounds to olefins by tungsten hexachloride-lithium aluminum hydride and some tungsten and molybdenum carbonyls. J. Org. Chem. 1978,43, 2477-2480. 

This reagent [M] reacts with carbonyl compounds in the ratio TiCls 3THF/ Mg/RiR2C=0 = 1 2.5 2 to form olefins or coupled vic-diols, often in high yield. Compare Tungsten hexachloride, 4, 569-570. 

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