Carbonyl metathesis

Metal oxide species with acid or basic properties as efficient catalysts for alkylation and related reactions have been discussed in Section 5.2. An alternative approach is based on reactions of covalent metal-to-carbon (M-C) bonds. Transition metals are well-suited for this task, as they form directional bonds using hybrid orbitals, and undergo low-energy electron promotion and transfer processes. There are now many industrial processes involving transition metal-catalyzed carbon-carbon bond formation (for example, carbonylation, metathesis, and polymerization reactions, see Chapters 4, 6 and 7, respectively). In sections 5.3-5.4 we deal with other C-C bond forming reactions that can lead to fine chemicals (see Chapter 1). 

In our previous book on domino reactions [4h], we have classified domino reactions according to the mechanism of the different steps. This organizing principal will also be used in this book, and you will find chapters about transition metal catalysis including carbonylation, metathesis and CH-activation, nucleophiHc substitutions, radical reactions, pericyclic reactions, Michael reactions, aldol reactions, oxidations, and reductions. 

Olefin metathesis Carbonyl-olefin Carbonyl metathesis (OM) metathesis (COM) (CM)... 

We named this mechanism carbene mechanism because of the transition metal carbene complexes present in the three cycles. If it is true, then the reactions can be named metathesis reactions -OM, carbonyl-olefin metathesis (COM) and carbonyl metathesis (CM), respectively. All of them are double bond formation reactions. It is easy to recognize in this chart not only the catalytic cycle of OM but the Grubbs strategy for the synthesis of cycloalkenes via alkylidene-mediated OM and carbonyl olefination [15] as well (Chart 4a). 

A catalytic metathesis reaction between an alkyne and a carbonyl compound provides an attractive method for the construction of highly substituted enones, as a result of an efficient and atom-economical manner as an alternative to the Wittig reaction (Scheme 24.70). The conventional procedure of alkyn-carbonyl metathesis requires excess BF3 x OEt2-... 

Intermolecular Alkyne-carbonyl Metathesis The catalytic intermolecular version of the alkyne-carbonyl metathesis provided a synthetic procedure for the... 

We found SbFs in the presence of alcohol-catalyzed alkyne-carbonyl metathesis of substituted phenylalkyne with aldehyde, and it was extended to the cascade reaction combined with the Nazarov cyclization of the formed alkenyl phenyl ketones such as 305 (Scheme 24.75). " In this sequence, an appropriate choice of alcoholic additive is critical for the efficient formation of indanone 306. A combination of intramolecular alkyne-carbonyl metathesis with Nazarov cyclization has been independently reported for the construction of polycyclic enone by Yamamoto et al. "... 

We also reported on the synthesis of 2,3-dihydroquino-lin-4(lfl)-one derivatives 309, which are expected to possess attractive pharmacological properties and serve as important synthetic intermediates. Thus, the catalytic alkyne-carbonyl metathesis of arylalkyne 307 followed by intramolecular addition of heteroatom nucleophile afforded... 

SCHEME 24.74. Alkyne-carbonyl metathesis of 1-phenyl-1-propyne and aldehydes. 

SCHEME 24.75. Formation of indanone via alkyne-carbonyl metathesis. 

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