The borrowing-hydrogen (or hydrogen autotransfer) process, where the catalyst dehydrogenates a substrate and formally transfers the H atom to an unsaturated intermediate, is an atom-efficient and environmentally benign transformation. Described here is an example of an asymmetric borrowing-hydrogen cascade for the formal anti-Markovnikov hydroamination of allyl alcohols to synthesize optically enriched γ-secondary amino alcohols. By exploiting the Ru-(S)-i PrPyme catalyst with minimal stereogenicity, a cascade process including dehydrogenation, conjugate addition, and asymmetric reduction was developed. The mild conditions, functional group tolerance, and broad substrate scope (54 examples) demonstrate the synthetic practicality of the catalytic system.
The mechanistic uniqueness and versatility of borrowing hydrogen catalysis provides an opportunity to investigate the controllability of ac ascade reaction, and more importantly,torealizeeither one or both of chiral recognition and chiral induction simultaneously.H ere we report that, in ab orrowing hydrogen cascade starting from racemic allylic alcohols,one of the enantiomers could be kinetically resolved, while the other enantiomer could be purposely converted to various targeted products,i ncluding a,b-unsaturated ketones, b-functionalized ketones and g-functionalized alcohols.B y employing ar obust Ru-catalyst, both kinetic resolution and asymmetric induction were achieved with remarkable levels of efficiency and enantioselectivity.D ensity functional theory (DFT) calculations suggest that corresponding catalyst-substrate p-p interactions are pivotal to realizet he observed stereochemical diversity.
A metal-free aerobic sulfenyllactonization of unsaturated carboxylic acids with thiols has been disclosed. This method proceeded with air as the sole oxidant, without any metal catalyst, which provides an efficient access to a wide range of sulfenylated lactones with moderate to good yields. The operational simplicity, high atom efficiency, scalability and the use of bio-based green solvent under mild conditions are the attractive features of this methodology.
The mechanistic uniqueness and versatility of borrowing hydrogen catalysis provides an opportunity to investigate the controllability of a cascade reaction, and more importantly, to realize either one or both of chiral recognition and chiral induction simultaneously. Here we report that, in a borrowing hydrogen cascade starting from racemic allylic alcohols, one of the enantiomers could be kinetically resolved, while the other enantiomer could be purposely converted to various targeted products, including α,β‐unsaturated ketones, β‐functionalized ketones and γ‐functionalized alcohols. By employing a robust Ru‐catalyst, both kinetic resolution and asymmetric induction were achieved with remarkable levels of efficiency and enantioselectivity. Density functional theory (DFT) calculations suggest that corresponding catalyst–substrate π–π interactions are pivotal to realize the observed stereochemical diversity.
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