Formation of medium-ring heterocycles by diene and enyne metathesis

Recent progress in the synthesis of oxepanes and medium ring ethers

“…82 Therefore, while there have been recent reports employing RCM for the preparation of medium ring oxacycles, we will not review those examples, but direct the reader to several lead references. 83 Herein,…”

Ring-Closing Metathesis Synthesis of Medium and Large Rings: Challenges and Implications for Sustainable Synthesis

“…Examples abound in recent reviews of important macrocyclic [2,3,[29][30][31][32][33][34][35] and medium-ring [28,30,[36][37][38][39] targets prepared by RCM, including natural products [40][41][42][43], compounds of biological and medicinal relevance [37,44,45], and topologically interesting molecules, including "molecular machines" [32,[46][47][48]. As the discussion of Section 2 suggests, however, RCM competes with oligomerization reactions (often described as "acyclic diene metathesis", ADMET), and observation of oligomers (in macrolide synthesis) [26] or cyclodimers (in attempted synthesis of cyclooctanoids) [49] dates back to the earliest reports.…”

Synthesis of Natural Products Containing Medium‐Size Oxygen Heterocycles by Ring‐Closing Alkene Metathesis

“…In contrast to Nicolaou's Tebbe reagent protocol, evidence is suggestive of an olefin metathesis, carbonyl-olefination cyclization mechanism [63a,b,f], [64d], [66]. 1) Subsequently, this reaction has been used by the Rainier 1) Grubbs has proposed a related mechanism for ring-opening metathesis, carbonylolefination reactions. group to generate subunits of adriatoxin, in a two-directional approach to libraries of polycyclic ethers and in olefinic-lactone cyclizations to medium rings [67][68][69].…”