Ruthenium dihydride complexes as enyne metathesis catalysts

A Dual CuH- and Pd-Catalyzed Stereoselective Synthesis of Highly Substituted 1,3-Dienes

“…Due to the utility of 1,3-dienes in organic synthesis, a variety of strategies to access these compounds have been developed. , Olefination of carbonyl compounds with stoichiometric allyl nucleophiles has been widely employed in the synthesis of conjugated dienes; − however, the products are generally obtained as inseparable E/Z mixtures (Figure A). , Although considerable advances have been made toward stereoselective olefination of carbonyl substrates, most methods to access 1,3-dienes result in the E,E- isomer. ,,, To avoid the formation of isomeric product mixtures, transition-metal-catalyzed cross-coupling utilizing preformed organometallic reagents and vinyl (pseudo)­halides has emerged as a practical route to stereoselectively synthesize dienes (Figure B). − In these processes, the geometry of the diene product is dictated by the stereochemistry of the coupling partners. Complementary approaches to prepare 1,3-dienes, including C–H activation of olefin starting materials, , rearrangements of allenes or alkynes, and ene-yne metathesis of acyclic precursors, , have also been developed. , …”

“…31−36 In these processes, the geometry of the diene product is dictated by the stereochemistry of the coupling partners. Complementary approaches to prepare 1,3dienes, including C−H activation of olefin starting materials, 37,38 rearrangements of allenes or alkynes, 39 and ene-yne metathesis of acyclic precursors, 40,41 have also been developed. 42,43 Our group and others have demonstrated the potential of CuH-catalyzed hydrofunctionalization reactions to enable unsaturated substrates to serve as surrogates for preformed organometallic reagents.…”

Modern Synthetic Methods for the Stereoselective Construction of 1,3-Dienes

“…More recently, Dolan et al described the use of ruthenium (IV) dihydride complexes as new catalysts for the metathesis of oxygenated and nitrogenated enynes ( Scheme 55 ) [ 183 ].…”

Six-Membered Ring Systems: With O and/or S Atoms

“…Cyclization reactions of allenic alcohols with aldehydes in dichloromethane at 0 C promoted by bismuth(III) trifluoromethanesulfonate leads to 3,6-dihydro-2H-pyrans while using trimethylsilyl trifluoromethanesulfonate (TMSOTf) at À45 C provides hexahydropyrano[4,3-b]pyrans (18JOC14987). Some 5,6-dihydro-2H-pyrans are obtained from enyne metathesis using ruthenium dihydride complexes as catalysts (18TL4471). A series of indolo[2,3-c]-5,6-dihydro-2H-pyrans were prepared via intramolecular oxa-PicteteSpengler reactions of 3-(2-vinyloxyethan-1-yl)indoles, under dual catalysis of urea and a chiral phosphoric acid in toluene at À40 C (18AGE17225).…”