A Putatively Unfeasible Heck Reaction − From Cyclopentenones to Annulated Ring Systems

Abstract

2‐Iodocyclopentenones undergo a Heck reaction with allylic and homoallylic alcohols, in acceptable yields, to give dicarbonyl compounds useful for the construction of annulated cyclopentanones. In contrast, the corresponding iodo‐substituted cyclohexenones, cycloheptenones and acyclic α,β‐unsaturated ketones are far less or even unsuitable for Heck reactions of this type.

Cascade Reactions during Coronafacic Acid Biosynthesis: Elongation, Cyclization, and Functionalization during Cfa7-Catalyzed Condensation

“…Unfortunately, due to the heterogeneity of the reaction mixture, detailed kinetics of the cyclization could not be performed. Nonetheless, the observation that the 6- endotrig cyclization rapidly occurs in the absence of Cfa7 indicates that the enzyme does not necessarily lower the energy barrier for cyclization. Rather, the formation of multiple stereoisomers in the absence of Cfa7 suggests that Cfa7 plays a role in controlling the stereochemistry of the cyclization.…”

Application of Aryl Siloxane Cross-Coupling to the Synthesis of Allocolchicinoids

“…This result is particularly noteworthy because it constitutes only the second example of the cross-coupling of an α-chloroenone. The coupling of iodides and bromides has been studied previously, but until recently, there was not an example of the coupling of a chloride substrate …”

Stereoselective Synthesis of the ABC Ring System of Aspterpenacids

“…The reaction was then warmed to 0 °C and stirred for 30 min. A solution of compound 17 (2 g, 13.1 mmol) in THF (10 mL) was then added dropwise via syringe, and the mixture was warmed to room temperature and stirred for 4 h. The reaction mixture was quenched with saturated aqueous NH 4 Cl (20 mL) and extracted with EtOAc (50 mL). The combined organic extracts were washed with water, dried over MgSO 4 , and concentrated in vacuo.…”

“…These unsuccessful Conia–ene cyclization attempts forced us to reconsider our strategy (Scheme ). From readily available diketone 17 , an olefination and reduction sequence afforded compound 19 in the racemic form. Following the same transformations described earlier, 19 was acylated, diazolated, and subjected to Cu-catalyzed cyclopropanation conditions to successfully afford tricyclic compound 22 .…”