O–H Activation and Addition to Unsaturated Systems

Mechanism Investigations of the Endo Cycloisomerization of Alkynols through Isolation and Characterization of Ruthenium Complexes from the Reactions of Alkynes with a Ruthenium Complex

“…Endocyclic enol ethers are very useful synthetic starting materials for the construction of diverse oxygen-containing heterocycles which are important structural units in a number of naturally occurring and biologically active molecules. − Catalytic endo cycloisomerization of alkynols represents the most straightforward approach to obtain endocyclic enol ethers, with the advantages of high efficiency and 100% atom economy . In the pioneering work in this area, McDonald and his co-workers discovered that molybdenum ,, and tungsten ,,− carbonyl complexes can effectively catalyze the endo cycloisomerization of a range of alkynols.…”

Efficient Intramolecular Hydroalkoxylation/Cyclization of Unactivated Alkenols Mediated by Lanthanide Triflate Ionic Liquids

“…The regioselective intramolecular addition of an O−H bond across C−C unsaturation is an atom-economical route to constructing both simple and complex oxygen-containing heterocycles, including important structural components of a wide array of naturally occurring and biologically active molecules, such as acetogenins and polyether antibiotics . Currently, cyclic ethers are accessible either by direct catalytic Wacker oxidative cyclization or intramolecular hydroalkoxylation (HO), − with the latter being a relatively unexplored area involving a limited number of reported catalysts. − Catalytic approaches to intramolecular HO processes have implemented Brønsted acid, transition metal, and metal triflate catalysts with varying degrees of success.…”

Atom-Efficient Carbon−Oxygen Bond Formation Processes. DFT Analysis of the Intramolecular Hydroalkoxylation/Cyclization of Alkynyl Alcohols Mediated by Lanthanide Catalysts

“…In this context, the catalytic addition of alcohols to alkynes represents a direct route for the synthesis of enol ethers and diverse oxygen-containing heterocycles via inter- or intramolecular reaction modes, respectively. Since addition reactions of this type can be performed, in principle, with total atom efficiency and with negligible waste formation, such processes fulfill green chemical requirements more satisfactorily than do byproduct-producing substitution reactions leading to the same products . Thus, in principle, many important and useful oxygen-containing organic compounds should be accessible via catalytic hydroalkoxylation, and straightforward and efficient routes to numerous oxygen-containing heterocycles should be accessible by specific intramolecular variants of this reaction.…”

“…Nevertheless, although catalytic intramolecular hydroalkoxylation offers many attractions compared to traditional heterocycle synthetic methodologies, efficient catalytic transformations remain a challenge because of several factors, such as the relatively large bond enthalpies of typical O−H σ-bonds and the modest reactivity of electron-rich olefins with nucleophiles. These problems have stimulated growing efforts to develop more efficient and selective hydroalkoxylation catalysts. − …”