Alkene metathesis medium rings synthesis

Macrolactone synthesis 6,51, 71, 72, 94, 124,131,163,187,195 McMurry coupling 43 Medium ring synthesis 43,45,75, 77 Metathesis, Alkene (see Grubbs) Metathesis, Alkyne (see alkyne metathesis) Michael addition Intramolecular 166,166, 167,201 Intermolecular 57,84, 153, 166,204... 

In cases where metathesis with the catalyst 84 is unsuccessful or very sluggish, then the Schrock catalyst 85 or catalysts such as 86 are often effective. This is particularly the case for the formation of tri- or tetrasuhstituted alkenes, which are normally too hindered to he formed using the catalyst 84. For example, ringclosing metathesis of the diene 91 is unsuccessful with the Grubbs catalyst 84, but the cyclohexene 92 can be formed in excellent yield with the catalyst 86 (2.113). An efficient synthesis of the medium-ring terpene dactylol 94 was accomplished with the Schrock catalyst 85 (2.114). Attempted metathesis of 93 with the catalyst 84 failed to give any of the medium-ring trisubshtuted alkene product. 

Synthesis of Natural Products Containing Medium-size Carbocycles by Ring-closing Alkene Metathesis... 

We will focus on the development of ruthenium-based metathesis precatalysts with enhanced activity and applications to the metathesis of alkenes with nonstandard electronic properties. In the class of molybdenum complexes [7a,g,h] recent research was mainly directed to the development of homochi-ral precatalysts for enantioselective olefin metathesis. This aspect has recently been covered by Schrock and Hoveyda in a short review and will not be discussed here [8h]. In addition, several important special topics have recently been addressed by excellent reviews, e.g., the synthesis of medium-sized rings by RCM [8a], applications of olefin metathesis to carbohydrate chemistry [8b], cross metathesis [8c,d],enyne metathesis [8e,f], ring-rearrangement metathesis [8g], enantioselective metathesis [8h], and applications of metathesis in polymer chemistry (ADMET,ROMP) [8i,j]. Application of olefin metathesis to the total synthesis of complex natural products is covered in the contribution by Mulzer et al. in this volume. 

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