Iridium-Catalyzed Enantioselective Synthesis of Allylic Alcohols

Angewandte Chemie International Edition, 45, Issue 37, Pages 6204-6207

The development of efficient processes that give rapid and easy access to optically active building blocks is of great importance, particularly for the synthesis of complex molecules. The metal-catalyzed asymmetric allylic substitution reaction, which involves the addition of a range of diverse nucleophiles to an allylmetal intermediate, is one of the most studied processes.[1] The use of Ir complexes in this transformation provides access to products that are complementary to those obtained from Pd catalysis.[2], [3] The types of nucleophiles that have been employed in Ir-catalyzed processes have included enolates derived from malonates, but recently other nucleophiles such as amines, phenols, and alkoxides have been used.[4]-[6] Omitted from this list is the use of hydroxide, or its equivalent, to give the corresponding product with a free alcohol. Herein, we describe the first example of an iridium-catalyzed enantioselective allylation involving the use of silanolates as nucleophiles, which allows convenient access to chiral allylic alcohols, useful building blocks in asymmetric synthesis [Eq. (1)]. The isolated products are formed in useful yields and 92-99 % ee.