Iridium‐Catalyzed Asymmetric Hydrogenation of 3,3‐Disubstituted Allylic Alcohols in Ethereal Solvents

Abstract

Ir-phosphinomethyl-oxazoline complexes have been identified as efficient, highly enantioselective catalysts for the asymmetric hydrogenation of 3,3-disubstituted allylic alcohols and related homoallylic alcohols. In contrast to other N,P ligand complexes, which require weakly coordinating solvents, such as dichloromethane, these catalysts perform well in more ecofriendly THF or 2-MeTHF. Their synthetic potential was demonstrated with the formal total synthesis of four bisabolane sesquiterpenes.

Synthetic Approaches to Mono- and Bicyclic Perortho-Esters with a Central 1,2,4-Trioxane Ring as the Privileged Lead Structure in Antimalarial and Antitumor-Active Peroxides and Clarification of the Peroxide Relevance

“…(E)-3-(2-Naphthyl)but-2-ene-1-ol ( 3c ) [ 53 ]. Following GP-2, 2.50 g (10.5 mmol) of ester 2c was reduced with 1.11 g (29.2 mmol, 2.8 eq) of LiAlH 4 in 16 mL of diethylether.…”

Direct Conversion of Aldehydes and Ketones into Azides by Sequential Nucleophilic Addition and Substitution

“…5 %. [11e], , Starting from the same initial precursor, the method reported here allows a direct synthesis, increases the overall yield by >10‐fold, and reduces the step count from 3 to 1.…”

Iridium‐Catalyzed Enantioselective Hydrogenation of Vinylsilanes

“…The range of substrates that have been successfully hydrogenated with these catalysts comprises a wide variety functionalized and unfunctionalized olefins. 11,[19][20][21][22][23][24] Even purely alkyl-substituted alkenes were found to react with excellent enantioselectivities and high turnover numbers. Therefore, we thought that alkenes bearing a silyl instead of an alkyl group should be feasible substrates as well.…”

“…As part of our long-term studies of Ir-catalyzed asymmetric hydrogenation, [11][12][13][14][15][16][17][18][19][20][21][22][23][24] we explored the potential of various classes of chiral Ir N,P-ligand complexes for the enantioselective hydrogenation of vinylsilanes. Ir complexes of this type have considerably enhanced the scope of asymmetric hydrogenation of olefins because they do not require the assistance of a coordinating group in vicinity of the C=C bond like Rh and Ru diphosphine complexes.…”

“…The latter clearly performed best, affording the desired product 8b with full conversion and 96% ee. The corresponding methyl-substituted vinylsilanes 7c and 7d as well gave high enantioselectivities with pyridine-based ligands 6a-c (entries [15][16][17][18][19][20]. The chloroalkyl-substituted vinylsilane 7e reacted with lower but still respectable enantioselectivity.…”