Cooperative Catalysis: Asymmetric Transformations with Unprotected Heteroatoms under Phase-Transfer Conditions
Final Report Abstract
In summary, the first alkylative kinetic resolution of vicinal diols under phase-transfer conditions could be realized. To render the anticipated reaction possible a co-catalytic approach between a borinic acid and a phase-transfer catalyst was used. The borinic acid as co-catalyst attenuated the basicity of the hydroxyl groups concomitant with the formation of a ridged borinate as intermediate, which afterwards could be recognized by the chiral phase-transfer catalyst to undergo smooth ion exchange. The reaction showed a broad scope and more than 40 compounds with ees over 80% at almost half conversion were synthesized. Additionally, a new synthetic route to phase-transfer catalyst 14 has been developed utilizing state-of-the-art ruthenium catalyzed C-H activation. Furthermore, an alkylative desymmetrization of simple diols such as cyclohexanediol was investigated, whereas the optimized reaction conditions displayed a very narrow scope and very long reaction times rendering a reinvestigation of the reaction conditions necessary. We envision that further development of this concept, for example by the use of a different cocatalyst, will render the asymmetric functionalization of mono-alcohols under asymmetric phasetransfer conditions possible.
Publications
- “Alkylative kinetic resolution of vicinal diols under phase-transfer conditions: a chiral ammonium borinate catalyst”, Chem. Sci., 2018, 9, 1231
M. Pawliczek, T. Hashimoto, K. Maruoka
(See online at https://doi.org/10.1039/c7sc04854h)
