Chemoselective Aromatic C–H Insertion of α-Diazo-β-ketoesters Catalyzed by Dirhodium(II) Carboxylates

Abstract

The ability of α-diazo-β-ketoesters bearing a substituent on the benzylic position to undergo aromatic C-H insertion is described. Good to excellent yields of the aromatic C-H insertion products were observed with Rh(2)(tpa)(4) or Rh(2)(esp)(2) catalysts. This is an attractive strategy to prepare tetralins carrying a methyl group on the benzylic position, a structural motif found in several types of natural products.

Synthetic Applications of Sulfur-based Chiral Auxiliaries in Asymmetric Syntheses

“…[39] The β-keto ester 20 was obtained by malonate displacement/decarboxylation of the oxazolidinethione in imide 19 utilizing potassium salt of monoethyl malonate and MgCl2 in the presence of imidazole (Scheme 7). [40] The corresponding α-diazo-β-ketoester 21 was prepared from the β-ketoester 20 and underwent an aromatic C-H insertion in the presence of Rh(II) catalyst.…”

Rhodium-Catalyzed Intramolecular Cyclopropanation of α-Diazo β-Keto Nitriles Containing an Unsaturated Substituted Cycloalkyl Group

“…In view of the observed instability of 4e and 4e′, we assume that these compounds might have resulted from spontaneous ring opening of the intermediates generated by cyclopropanation to release the strain of the twisted tetracyclic ring system (Scheme 10). 22 Nevertheless, the possibility of another pathway involving aromatic C-H insertion followed by in situ epimerization 23 has not been excluded. Regardless of which mechanism operates, it is noteworthy that this finding represents an unprecedented route for producing hexahydrophenanthrene or tetrahydrocyclopentanaphthalene derivatives, which have received much attention in synthetic endeavors, owing to their interesting biological profiles and broad utility in organic synthesis.…”

Selective Functionalization of Aromatic C(sp2)−H Bonds in the Presence of Benzylic C(sp3)−H Bonds by Electron‐Deficient Carbenoids Generated from 4‐Acyl‐1‐Sulfonyl‐1,2,3‐Triazoles

“…An intramolecular reaction successfully occurred with the 4‐(3‐phenylpropanoyl)‐1,2,3‐triazole ( 18 ; Scheme a) . A six‐membered‐ring product ( 19 ) was formed in 94 % yield through intramolecular insertion at the aromatic C(sp 2 )−H bonds.…”