Synthesis 2013; 45(20): 2824-2831
DOI: 10.1055/s-0033-1338512
practical synthetic procedures
© Georg Thieme Verlag Stuttgart · New York

A Practical Synthetic Approach to Chiral (α-Chloroalkyl)boronic Esters via Iridium-Catalyzed Chemoselective Hydrogenation of Chloro-Substituted Alkenyl Boronates

Stephen J. Roseblade
a   Johnson Matthey, Catalysis and Chiral Technologies, Unit 28, Cambridge Science Park, Milton Road, Cambridge CB4 0FP, UK
,
Eva Casas-Arcé
a   Johnson Matthey, Catalysis and Chiral Technologies, Unit 28, Cambridge Science Park, Milton Road, Cambridge CB4 0FP, UK
,
Ulrike Nettekoven
b   Solvias AG, Business Unit Synthesis and Catalysis, Römerpark 2, 4303 Kaiseraugst, Switzerland
,
Ivana Gazić Smilović
c   Lek Pharmaceuticals, d.d., Sandoz Development Center Slovenia, API Development, Organic Synthesis Department, Kolodvorska 27, 1234 Mengeš, Slovenia
,
Antonio Zanotti-Gerosa
a   Johnson Matthey, Catalysis and Chiral Technologies, Unit 28, Cambridge Science Park, Milton Road, Cambridge CB4 0FP, UK
,
Zdenko Časar*
c   Lek Pharmaceuticals, d.d., Sandoz Development Center Slovenia, API Development, Organic Synthesis Department, Kolodvorska 27, 1234 Mengeš, Slovenia
d   Sandoz GmbH, Global Portfolio Management API, 6250 Kundl, Austria   Fax: +43(5338)200418   Email: zdenko.casar@sandoz.com
e   Faculty of Pharmacy, University of Ljubljana, 1000 Ljubljana, Slovenia
› Author Affiliations
Further Information

Publication History

Received: 26 June 2013

Accepted: 01 July 2013

Publication Date:
01 August 2013 (online)


Dedicated to Prof. Dr. Dominique Lorcy (University of Rennes 1, France) on the occasion of her birthday

Abstract

Chiral (α-chloroalkyl)boronic esters are obtained by homogeneous asymmetric iridium-catalyzed chemoselective hydrogenation of (1-chloro-1-alkenyl)boronic esters. P,N–Iridium catalysis provides low level of dehalogenation during the hydrogenation, while the catalyst activity and enantioselectivity essentially depends on the applied P,N ligand features. Fine tuning of P,N ligand structures enables high conversions, broad substrate acceptance, and high to excellent enantioselectivities with enantiomeric excess values up to 94% along with low levels of dechlorination. Low catalyst loading with S/C = 200 can also be achieved for the preparation of an industrially important isobutyl derivative.