A facile and practical methodology for the synthesis of synthetically useful diarylmethanol-based 1,4-diols and enantiomerically pure BINOL-derived diols with axial and sp(3)-central chirality has been developed through neighboring lithium-promoted [1,2]-Wittig rearrangement. The chirality transfer process shows a broad substrate scope in terms of the aromatic ether substituent, which allows access to a broad of range of chiral 1,1'-binaphthalene-2-α-arylmethanol-2'-ols with excellent enantioselectivities (>99 % enantiomeric excess) and yields (84-96 %). This should be considered as an available and attractive chiral source to design and prepare privileged ligands or catalysts.
We have demonstrated a highly diastereoselective synthesis of optically pure Ar‐BINMOL‐derived diols and their analogues. The present study demonstrates a unique cascade chirality transfer in a [1,2]‐Wittig rearrangement that leads to chiral diols with three stereogenic centers, which include a chiral sp3 center at the alcohol and C2‐axial chirality. Screening these ligands in the arylation of aromatic aldehydes with Grignard reagents shows that the naphthyl‐substituted BINMOL promotes the aryl transfer reaction in good yields (70–92 %) and moderate‐to‐good enantioselectivities (up to 72 % ee), and a series of control experiments substantiates that the axial chirality and the chiral sp3 center at the alcohol of the Ar‐BINMOLs are the pivotal enantioselectivity‐controlling structure elements. In addition, this study demonstrated the importance of the chiral sp3 center at the alcohol on Ar‐BINMOL for the aryl transfer reaction. Finally, we found that the chiral Ar‐BINMOL ligand 2h mediated the titanium‐promoted 1,2‐addition of MeMgBr to aldehydes to give the desired products in good yields with excellent enantioselectivities (up to 92 % ee).
A very simple method was developed for the direct, palladium-free catalytic a-allylic alkylation of aldehydes. The direct organocatalytic intermolecular a-allylic alkylation reaction was mediated by a simple combination of Brønsted acid and enamine catalysis which furnished a-allylic alkylated aldehydes and cyclohexanone in high yields and chemoselectivities. The reaction conditions are mild and environmental friendly, the process is conducted under an atmosphere of air without the need for dried solvents, and water is the only side product of the allylic alkylation reaction.
The catalytic activation of sp 3 -carbon-nitrogen of allylic amides is generally difficult because of the inefficient leavinggroup ability of the amide group. In this article, we have discovered for the first time that FeCl 3 -catalyzed Tsuji-Trost coupling reaction of aromatic allylic amides with active methylene compounds, cyclohexanone, and allytrimethylsilane work efficiently under mild conditions.
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