Reactions of Higher Nuclearity Chromium and Tungsten Carbenes

Reactions of Higher Nuclearity Chromium and Tungsten Carbenes 

The addition of amines to a,/3-unsaturated alkoxycarbene complexes is temperature dependent. At low temperature (-78 °C) 1,4-addition (Michael addition) is overruled by direct addition of the amine at the carbene carbon atom (aminolysis). 

Metathesis Reactions Catalyzed by Croup VI and VIII Metal Carbenes 

Compared to Grubbs catalyst 143, the Schrock-type catalysts like commercially available 142b are more sensitive to moisture and oxygen and less compatible with functional groups on the other hand, they are generally more reactive and, for instance - in contrast to 143 - allow for the formation of tri- and tetrasubsti-tuted double bonds. 

Molybdenum-catalyzed ARCM has been applied to the enantioselective synthesis of 7- or 8-membered heterocycles [83] as well as for midsized cyclic tertiary amines [84]. Chiral molybdenum catalysts allow for efficient kinetic resolution of 1,6-dienes and diallyl ethers. 

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Reactions of Higher Nuclearity Chromium and Tungsten Carbenes I 469... 

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