Copper-catalyzed asymmetric allylic substitution reactions with boron and silicon reagents

Our recent studies on copper catalysis revealed that arenol-N-heterocyclic carbenes were privileged chiral ligands for asymmetric copper-catalyzed allylic substitution reactions [1–4]. This presentation will focus on the... [ view full abstract ]

Our recent studies on copper catalysis revealed that arenol-N-heterocyclic carbenes were privileged chiral ligands for asymmetric copper-catalyzed allylic substitution reactions [1–4]. This presentation will focus on the reactions using allylboronates as pronucleophiles or hydrosilanes as reagents for generating formyl nucleophiles.

As for boron, Cu-catalyzed enantioselective allyl–allyl coupling between allylboronates and (Z)-allylic phosphates will be reported.[3] This reaction occurred with exceptional S_N2’-type regioselectivities and high enantioselectivities to deliver chiral 1,5-diene derivatives with a tertiary carbon stereogenic center at the allylic/homoallylic position. This reaction was enabled by a combined use of our original chiral phenol-carbene ligand as a functional Cu-supporting ligand and KOMe as a stoichiometric Lewis base for B.

As for silicon, Cu-catalyzed asymmetric three-component coupling reaction between isocyanides, hydrosilanes, and γ,γ-disubstituted primary allylic phosphates (chlorides) yielding chiral α-quaternary formimides will be reported.[4] The formimides were readily converted to the corresponding α-quaternary aldehydes. This highly selective reaction was enabled by a combined use of a chiral naphthol-carbene as a ligand for Cu and LiOtBu as a stoichiometric Lewis base for Si.

[1] Harada, A.; Makida, Y.; Sato, T.; Ohmiya, H.; Sawamura, M. J. Am. Chem. Soc. 2014, 136, 13932.

[2] Ohmiya, H.; Zhang, H.; Shibata, S.; Harada, A.; Sawamura, M. Angew. Chem. Int. Ed. 2016, 55, 4777.

[3] Yasuda, Y.; Ohmiya, H.; Sawamura, M. Angew. Chem. Int. Ed. 2016, 55, 10816.

[4] Hojoh, K.; Ohmiya, H.; Sawamura, M. J. Am. Chem. Soc. 2017, 139, 2184.