Methods of formation of the ether linkage

Enantioselective synthesis of hindered cyclic dialkyl ethers via catalytic oxa-Michael/Michael desymmetrization

“…Limitations of classical methods for the preparation of tertiary ethers, such as the Williamson ether synthesis, include undesirable racemization and elimination pathways. 1 Current C–O bond forming methodologies to address these limitations include metal-mediated alkene functionalizations, 2 carbonyl ylide cycloadditions, 3 among others; 4 intramolecular C–O bond formation with creation of a single α-stereocenter is common. A more powerful method for complexity-building synthesis could arise from intermolecular C–O bond formation allowing the preparation of α-tertiary ethers where both α-stereocenters are set in a single operation, but examples of these are rare.…”

“…11 Gaunt demonstrated the potential to perform direct enantioselective dearomatization reactions of phenols employing PhI(OAc) 2 in conjunction with enamine catalysis (Scheme 2a), 11 d while Rovis developed enantioselective synthesis of endoperoxide acetals by desymmetrization of the achiral hydroperoxides (Scheme 2b). 11 j p -Quinol 1 possesses both a tertiary alcohol capable of participating in intermolecular oxa-Michael addition and enantiotopic π-electrophiles for subsequent intramolecular desymmetrization. We proposed that these attributes could establish p -quinol 1 as a competent substrate class for iminium/enamine oxa-Michael/Michael cascade reactions under secondary amine catalysis.…”

The Regio‐ and Stereospecific Intermolecular Dehydrative Alkoxylation of Allylic Alcohols Catalyzed by a Gold(I) N‐Heterocyclic Carbene Complex

“…[1] As a result, considerable effort has been directed toward the development of efficient and selective methods for the synthesis of allylic ethers. [2,3] The transition metal-catalyzed alkoxylation of allylic alcohol derivatives represents an attractive route to allylic ethers with the potential to form C–O bonds under mild conditions and with high levels of regio- and stereocontrol. [3,4] Indeed, Pd 0 , [5] Rh II , [6] Ru, [7] and Ir I [8] complexes catalyze the alkoxylation of allylic carboxylates, carbonates, and related substrates with metal alkoxides, silanoates, alcohols, and phenols, and a number of these transformations occur with high enantioselectivity.…”

DendriMacs. Well-Defined Dendritically Branched Polymers Synthesized by an Iterative Convergent Strategy Involving the Coupling Reaction of AB2 Macromonomers

“…Other solvents that meet requirement b) include acetone, acetonitrile and dimethylsulphoxide all of which are non solvents for polystyrene. The 'textbook' good solvents for polystyrene, toluene and benzene, both have very low dielectric constants and therefore the only other viable solvent we could investigate was tetrahydrofuran (THF 40 . In contrast to DMF, the reaction in THF proceeded very slowly, after 150 minutes at reflux there was no apparent reaction and even after 5 days at reflux the extent of reaction was only a fraction of that observed in DMF.…”