Carbene complexes synthetic applications

Abstract For many years after its discovery, olefin metathesis was hardly used as a synthetic tool. This situation changed when well-defined and stable carbene complexes of molybdenum and ruthenium were discovered as efficient precatalysts in the early 1990s. In particular, the high activity and selectivity in ring-closure reactions stimulated further research in this area and led to numerous applications in organic synthesis. Today, olefin metathesis is one of the... 

The synthetic principles underlying the preparation of the 1 1 carbene complexes (above) are also applicable to products with a 2 1 ligand/metal ratio . The carbene components may be introduced as free carbenes or their dimers, or generated in situ from the onium salts. A second major pathway uses anionic hetero-... 

Another synthetic application of olefin metathesis using a thioacetal-titanocene(II) system is the ring-closing olefin metathesis (RCM) of carbene complexes possessing an olefin moiety, e. g. 33 (Scheme 14.17). The success of the RCM apparently depends on the substituents at the carbon—carbon double bond (i. e. the substituent(s) on the resulting carbene complex 34). 

Synthetic Applications of Heteroatom-Substituted Carbene Complexes... 

There are only a few reactions in which substituted benzenes are constructed in one step and with predictable regioselectivity. Carbene-complex-mediated benzannulations are one of these. Because of the scarcity of reliable benzannulation reactions, the use of carbene complexes for this purpose has become one of the most valuable synthetic applications of these organometallic reagents. 

Synthetic Applications of Non-Heteroatom-Substituted Carbene Complexes 105... 

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