Rh(III)-Catalyzed Aryl and Alkenyl C–H Bond Addition to Diverse Nitroalkenes

Abstract

The transition metal catalyzed C–H bond addition to nitroalkenes has been developed. Very broad nitroalkene scope was observed for this Rh(III)-catalyzed method, including for aliphatic, aromatic and β,β-disubstituted derivatives. Additionally, various directing groups and both aromatic and alkenyl C–H bonds were effective in this transformation. Representative nitroalkane products were converted to dihydroisoquinolones and dihydropyridones in a single step and in high yield by iron mediated reduction and in situ cyclization. Moreover, preliminary success in enantioselective Rh(III)-catalyzed C–H bond addition to nitroalkenes was achieved as was X-ray structural characterization of a nitronate intermediate.

Pentamethylcyclopentadienyl rhodium(III)–chiral disulfonate hybrid catalysis for enantioselective C–H bond functionalization

“…46,47 Realizing a similar process via C-H bond activation can circumvent the use of stoichiometric amounts of organometallic reagents. A series of racemic reactions were reported using Cp*Rh(III) [48][49][50] and Cp*Co(III) [51][52][53] catalysts, but catalytic stereocontrol was achieved only in the reaction with nitroalkenes using a chiral Cp x Rh(III) catalyst. 50…”

Rh‐Catalyzed Carboxylates Directed C–H Activation for the Synthesis of ortho‐Carboxylic 2‐Arylethenesulfonyl Fluorides: Access to Unique Electrophiles for SuFEx Click Chemistry

“…It was also notable that ortho ‐methyl‐, chloro‐, and bromo‐substituted substrates afforded mixtures of several unidentified compounds rather than the desired pure products under the standard conditions, while ortho ‐methoxy‐substituted substrate 1d gave the corresponding pure product 3d in 99 % yield. The reason that ortho ‐methyl‐, chloro‐, and bromo‐substituted substrates generated unidentified mixtures could be attributed to the conjugate addition between ortho C–H bonds of the arylcarboxylic ester and Michael acceptor ESF . The trifluoromethoxy‐substituted substrate 1j was also smoothly transformed into its corresponding product 3j .…”

C–H Functionalization of Aromatic Amides

“…In 2017, Ellman and co‐workers reported the first transition metal‐catalyzed ortho‐ C–H alkylation of aromatic amides using nitroolefins as coupling ligands (Scheme ) . The highlight of the method is that there are no strict restrictions on the directing groups and the nitroolefin substrates, and it is well tolerant to air and other ambient conditions.…”