An Aged Precatalyst Solution Leads to High Catalytic Activity: Oxidative Cyclization of 1,5-Dienes Using ppm Amounts of Ruthenium

Nickel-catalyzed allyl–allyl coupling reactions between 1,3-dienes and allylboronates

A nickel-hydride catalysis has been developed to facilitate the allyl–allyl cross-coupling reactions between 1,3-dienes and allyl-B(pin) in excellent regioselectivity.

Regioselective dehydration of α-hydroxymethyl tetrahydrofurans using Burgess' reagent under microwave irradiation

We here present a highly efficient and high yielding procedure for the preparation of 2-vinyl tetrahydrofurans starting from α-hydroxymethyl tetrahydrofurans. Best results for this dehydration were achieved using Burgess' reagent in dioxane under microwave irradiation. A range of functional groups as well as different cyclic and bicyclic frameworks were found to be compatible with the reaction conditions. The desired products were obtained within minutes in good to high yields and excellent regioselectivity.

The direct oxidative diene cyclization and related reactions in natural product synthesis

The direct oxidative cyclization of 1,5-dienes is a valuable synthetic method for the (dia)stereoselective preparation of substituted tetrahydrofurans. Closely related reactions start from 5,6-dihydroxy or 5-hydroxyalkenes to generate similar products in a mechanistically analogous manner. After a brief overview on the history of this group of transformations and a survey on mechanistic and stereochemical aspects, this review article provides a summary on applications in natural product synthesis. Moreover, current limitations and future directions in this area of chemistry are discussed.