Subscribe to RSS
DOI: 10.1055/s-0033-1340445
Enantioselective Hydrogenation of Chloro-Substituted Alkenyl Boronates
A Practical Synthetic Approach to Chiral (α-Chloroalkyl)boronic Esters via Iridium-Catalyzed Chemoselective Hydrogenation of Chloro-Substituted Alkenyl Boronates.
Synthesis 2013;
45: 2824-2831
Publication History
Publication Date:
13 December 2013 (online)
![](https://www.thieme-connect.de/media/synfacts/201401/i_l155_s1_10-1055_s-0033-1340445.gif)
Significance
Enantioenriched (α-chloroalkyl)boronic esters represent an important class of building blocks frequently used in organic synthesis. These chiral halogenated compounds are most commonly synthesized via Matteson-type rearrangements which use stoichiometric lithiated reagents, leading to stoichiometric waste streams. Transition-metal-catalyzed asymmetric hydrogenation has become the premier method for setting diversely substituted stereocenters with high enantiomeric excess under more environmentally friendly conditions. The authors report the synthesis of enantioenriched (α-chloroalkyl)boronic esters via the iridium-catalyzed asymmetric hydrogenation of chloro-substituted alkenyl boronates.
#
Comment
The authors present a protocol for the enantioselective iridium-catalyzed hydrogenation of chloro-substituted alkenyl boronates using a ferrocenyl phosphinoimidazoline ligand. Good to excellent yields and enantioselectivities were obtained for both alkyl- and aryl-bearing substrates. Substrate-to-catalyst ratios (S/C) of up to 25 and hydrogen pressures as low as 5 bar are reported. This catalytic system benefits from a low amount of dechlorinated products resulting from over-reduction.
#
#
![](https://www.thieme-connect.de/media/synfacts/201401/i_l155_s1_10-1055_s-0033-1340445.gif)