Rh₂(ii)-catalyzed enantioselective intramolecular Büchner reaction and aromatic substitution of donor–donor carbenes

Abstract

Chiral dirhodium(II) tetracarboxylate-catalyzed the enantioselective intramolecular Büchner reaction of donor/donor-carbenes was reported and a series of valuable chiral polycyclic products were synthesized. Both aryloxy enynones and diazo compounds were efficient...

Asymmetric Three-Component Reaction of Enynal with Alcohol and Imine as An Expeditious Track to Afford Chiral α-Furyl-β-amino Carboxylate Derivatives

“…The versatile reactivity of carbene species has made it one of the most important and useful synthons in synthetic chemistry since it was first discovered . Recently, enynones/enynals have been applied to different carbene reactions as reliable and stable non-diazo carbene precursors. , In these transformations, the key step is the catalytic 5-exo-dig cyclization to in-situ generate the α-furyl carbene species, which has been disclosed as a typical donor–donor-type metal carbene intermediate and applied to the expeditious synthesis of furan derivatives with structural diversity and atom economy (Scheme a). − However, in this area, the catalytic asymmetric versions using this in-situ-generated α-furyl carbene species are very rare, including X-H insertion, C-H insertion, cyclopropanation, and few others, , providing the chiral furan derivatives with a stereocenter on the benzylic position. On the other hand, the multicomponent reactions (MCRs) through interception of the in-situ-generated ylide intermediate (or its enolate and enol analogues) derived from diazo compounds and nucleophiles (RXH) have become a powerful method for the rapid construction of molecule complexity (Scheme b). − Moreover, by introduction of the metal and organocatalyst cooperative catalysis strategy, a variety of asymmetric metal carbene gem -bifunctionalization reactions have been realized for the direct assembly of chiral poly-functionalized carbonyl compounds .…”

A ligand-enabled, copper(ii)-catalyzed, highly selective and efficient synthesis of 2E-alkenylfurans from ynenones

“…Ynenones have been reported for the synthesis of furan derivatives 4 in the presence of transition-metal catalysts such as gold, palladium, silver, rhodium, and copper. 5–10 Most of the reported reactions have been proposed to proceed after carbene insertion or dimerization of α-furyl metal carbene intermediates, during which an air-free environment is required (Scheme 1A). Moreover, the in situ -generated α-furyl carbene complexes A from ynenones can be oxidized readily to 2-acyl furan 9 b ,10 c in an air atmosphere, and even an alkyl group can be installed at the end of an alkyne (Scheme 1A).…”

Divergent synthesis of benzazepines and bridged polycycloalkanones via dearomative rearrangement

“…From the perspective of arene substrates, most methods typically rely on low aromaticity arenes, such as phenol 6 , 7 , π-extended (hetero)arenes 8 , 9 , and hapto-coordinated arenes 10 . In terms of the thermodynamic profiles, highly active species such as cation 11 , carbene 12 – 15 , radical 16 , photoexcited intermediates 17 , 18 , and allyl organometallics; 19 , 20 were usually applied in order to compensate the enthalpic penalty in breaking an aromatic system. In this vein, catalytic asymmetric dearomatization has become a powerful method in achieving optically pure molecules from arenes 2 , 21 – 24 .…”