Rhodium-Catalyzed Asymmetric 1,4-Addition of Organoboronic Acids and Their Derivatives to Electron Deficient Olefins

Abstract

Asymmetric 1,4-arylation and -alkenylation was achieved by use of organoboronic acids or their derivatives in the presence of a rhodium catalyst coordinated with binap ligand. The reaction conditions are unique in that it is usually carried out in an aqueous solvent at 100°C. The scope of this asymmetric addition is very broad, a,b-unsaturated ketones, esters, 1-alkenylphosphonates, and 1-nitroalkenes being efficiently converted into the corresponding optically active 1,4-addition products with over 95% enantioselectivity. The catalytic cycle is proposed to involve the enantioselective addition of aryl-or alkenyl-rhodium intermediate to carbon-carbon double bond of the electron deficient olefins as a key step.

Synthesis and characterization of κ-2-bis-N-heterocyclic carbene rhodium(I) catalysts: Application in enantioselective arylboronic acid addition to cyclohex-2-enones

“…This suggests a small amount of water in the system is beneficial and that a fine balance between water-mediated catalyst activation and degradation exists. These results are in agreement with the findings of Hayashi [71,72].…”

Rhodium‐ and Palladium‐Catalyzed Asymmetric Conjugate Additions

“…Remarkably, in these NMR experiments all of the elementary steps readily occurred at 25 • C. This was in contrast to the reaction catalyzed by [Rh(acac)(binap)] (6), which required a temperature of 100 • C in order for it to occur. This apparent discrepancy in activity was pinpointed to the presence of acac-H in the reaction mixture when [Rh(acac)(binap)] was used.…”

“…The chapter is not intended to be comprehensive, and will include only selected examples of this powerful methodology. For more in-depth and comprehensive accounts, the reader should consult a number of excellent reviews that are available on this subject [6][7][8][9][10][11][12][13][14][15][16]. The first example of conjugate addition of an arylboronic acid to an enone catalyzed by transition metal complexes can be traced back to a report from 1995 by Uemura and coworkers [1].…”

Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones

“…Although this approach has been employed extensively in syntheses of compounds in which Y = CH 2 (tetralones) [34] it has been less frequently utilized with 4-chromones, due to the ease of phenoxide elimination after enolate formation. [6,11] Until recently, these methods for accessing flavanoids required capture of the newly formed enolate with a suitable electrophile such as benzaldehyde or chlorotrimethylsilane.…”