Tungsten complexes alkylation

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

Other derivatives can effect such functionalizations, including iron, ruthenium, rhodium, and tungsten complexes. Excellent regioselectivities were observed in catalytic thermal processes involving unfunctionalized alkanes and primary alkyl C-H bonds were functionalized (Equation (20)).31... 

A. ALKYL AND ARYL(tjs-CYCLOPENTADIENYL)DINITROSYL CHROMIUM, MOLYBDENUM, AND TUNGSTEN COMPLEXES... 

As described in many reviews, Trost and his co-workers have carried out a pioneering work on the molybdenum-and tungsten-catalyzed allylic alkylation of allylic esters regioselectivity of the reaction is often complementary to the palladium-catalyzed allylic alkylation. The first asymmetric version was disclosed by Pfaltz and Lloyd-Jones in 1995 (Equation (63)). They used a catalytic amount of a novel tungsten complex, prepared from [W(CO)3(MeCN)3] or [W(cycloheptatriene) (COIs] and optically active (diphenylphosphino)phenyloxazolines 57, for the allylic alkylation of 3-aryl-2-propenyl phosphate with dimethyl sodiomalonate to isolate the corresponding branched alkylated compounds as a major isomer with an excellent enantioselectivity (96% ee). Unexpectedly, 3-aryl-2-propenyl carbonates are shown to be unreactive. It is worth noting that an isostructural molybdenum complex does not promote the catalytic alkylation under the same reaction conditions. In contrast, Lloyd-Jones and Lehmann reported the stereocontrolled... 

The metal, M, can be Fe, Ru, Os (with n = 4) or Cr (n = 5). Substituents on silicon can vary widely, including aryl, alkyl, alkoxy and Et2N groups. With a slight modification, the same reaction is useful for silylene-tungsten complexes (equation 98). 

Comparison of the second-rate order constants for reactions of the molybdenum and tungsten analogs with a given alkyl halide shows that the tungsten complex reacts six times faster than the molybdenum counterpart (Section VI,E,2). 

Fig. 10. Molecular structure of the zirconoxycarbene tungsten complex 104 obtained by diastereoselective alkylation of 103.

K.-Y. Shih, K. Totland, S. W. Seidel, and R. R. Schrock, Spontaneous Loss of Molecular Hydrogen from Tungsten(IV) Alkyl Complexes to Give Alkylidyne Complexes, J. Am. Chem. Soc. 116, 12103-12104(1994). 

To date, low volumes of materials have been produced commercially from norbomene and cyclo-octene. Numerous products are expected to result from the materitd produced by the ROMP of dicyclopentadiene in a RIM (reaction injection molding) process. In a RIM process, two streams of a monomer are mixed in the mold where it is polymerized to the final part. In this case, one of the monomer streams contains a tungsten complex while the second contains an alkyl aluminum activator. When the two streams of dicyclopentadiene are mixed, the metathesis catalyst is formed and the monomer is ROMP polymerized (equation 12). 

---