Intermolecular 1,3-dipolar cycloadditions of müchnones with acetylenic dipolarophiles: Sorting out the regioselectivity

Photogeneration and Thermogeneration of Carbonyl Ylides: 1,3-dipolar Cycloadditions of 2,3-diaryloxiranes to Dipolarophiles*

A series of symmetrically substituted 2,3-diaryloxiranes 1 4 (Fig. 1) has been studied as photoprecursors for carbonyl ylides [l 31. The stereochemistry of the adducts obtained on the interception of these 4rzn transient system with a variety of dipolarophiles provides information on the mode(s) of electrocyclic opening of the oxiranes to carbonyl ylides as well as on the mechanism of the 4n + ...

Iridium–catalyzed 1,3–dipolar cycloadditions

1,3–Dipolar cycloaddition reactions (DCR) are atom–economic processes that permit the construction of heterocycles. Their enantioselective versions allow for the creation of up to four adjacent chiral centers in a concerted fashion. In particular, well–defined half–sandwich iridium (III) catalysts have been applied to the DCR between enals or methacrylonitrile with nitrones. Excellent yield and...

Cyclizations and cycloadditions of acetylenic sulfones on solid supports.

Acetylenic sulfones attached to solid supports by means of ester linkers were employed in a variety of cyclization and cycloaddition reactions, followed by cleavage of the products from the resin by ester hydrolysis or reductive desulfonylation.

Enantioselective copper-catalyzed 1,3-dipolar cycloadditions.

Enantioselective 1,3-dipolar cycloadditions of diazoacetates with electron-deficient olefins.

[reaction: see text] A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to beta-substituted, alpha-substituted, and alpha,beta-disubstituted alpha,beta-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive alpha,beta-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyraz...