Variation 3 Ring-Closing Metathesis

An elegant traceless linker variation on the ring-closing metathesis strategy resulted in the preparation of the tetrahydroazepine 201 from the immobilized diene 200, although the yield of 201 was only moderate (Equation 26) <1998EJ02583>. 

Attention paid to olefin metathesis in organic synthesis has increased over recent years because of the progress in ring-closing metathesis [3]. This metathesis variation consists of the cycliza-tion of an acyclic (a, cu)-diene 5 and formation of... 

Recently, chiral molybdenum catalysts such as 11 have been synthesized, giving access to asymmetric ring-closing metathesis [7]. Water-soluble variations of catalyst 10, like catalyst 12, perform metathesis in water or methanol [8], extending the scope of the reaction to substrates which are poorly soluble in organic solvents. 

Another important variation of a metathesis reaction is Ring-Closing Metathesis or RCM, a simplified generic example of which is shown in Eq. 

Fig. 4.12. Another variation of the olefin metathesis reaction ring-closing metathesis (RCM).

Fig. 4.23. A variation of the alkyne metathesis reaction ring-closing alkyne metathesis (RCAM).

Olefin metathesis [35] regioselectively ligates two olefinic sp -hybridized carbon atoms in an inter- or intramolecular sense and represents the most unusual carbon-carbon bond coupling for the synthesis of complex molecules. The latter variation is called ring-closing olefin metathesis [36] and has received considerable... 

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