Chain walking of allylrhodium species towards esters during rhodium-catalyzed nucleophilic allylations of imines

Allylrhodium species derived from δ-trifluoroboryl β,γ-unsaturated esters undergo chain walking towards the ester moiety.The resulting allylrhodium species react with imines to give products containing two new stereocenters and a Z-alkene. By using a chiral diene ligand, products can be obtained with high enantioselectivities, where a pronounced matched/mismatched effect with the chirality of the allyltrifluoroborate is evident

Enantioselective Rhodium-Catalyzed Allylation of Cyclic Imines with Potassium Allyltrifluoroborates

This Article presents further examples of the enantioselective rhodium-catalyzed addition of potassium allyltrifluoroborates to cyclic imines. A wide range of substituted allyltrifluoroborates are compatible with this process, and provide protected homoallylic amines with high levels of diastereo- and enantioselection. The reactions display a strong preference for carbon‒carbon bond formation at the more substituted terminus of the allyl fragment of the allyltrifluoroborate, regardless of the position of the boron atom. Representative examples of manipulation of the products are also described

Enantioselective Synthesis of Sealutomicin C

The sealutomicins are a family of anthraquinone antibiotics featuring an enediyne (sealutomicin A) or Bergman-cyclized aromatic ring (sealutomicins B–D). Herein we report the development of an enantioselective organocatalytic method for the synthesis of dihydroquinolines and the use of the developed method in the total synthesis of sealutomicin C which features a transannular cyclization of an aryllithium onto a γ-lactone as a second key step

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

Brønsted acid-catalysed conjugate addition of photochemically generated a-amino radicals to alkenylpyridines

The conjugate addition of a-amino radicals to alkenylpyridines has been accomplished by the synergistic merger of Brønsted acid and visible light photoredox catalysis. Key to reaction development was the protonation of the alkenylpyridines that transiently generated a highly reactive, electrophilic pseudo-iminium ion intermediate. Initial investigations using chiral phosphoric acids provide clues on the feasibility of an enantioselective catalytic variant

Light-triggered Enantioselective Organocatalytic Mannich-type Reaction

Abstract Disclosed herein is a photochemical organocatalytic strategy for the direct enantioselective Mannich-type reaction of 2-alkyl-benzophenones and cyclic imines. The chemistry exploits the light-triggered enolization of 2-alkyl-benzophenones to generate transient hydroxy-o-quinodinomethanes. These fleeting intermediates can be stereoselectively intercepted by imines upon activation with a chiral organic catalyst, derived from natural cinchona alkaloids. The developed method uses mild conditions, simple sources of illumination and easily available substrates and catalysts, affording enantioenriched chiral amines that are difficult to synthesize by other approaches. &nbsp;</p

Direct Stereoselective Installation of Alkyl Fragments at the β‑Carbon of Enals via Excited Iminium Ion Catalysis

The direct introduction of sp³ carbon fragments at the β position of α,β-unsaturated aldehydes is greatly complicated by competing 1,2-addition manifolds. Previous catalytic enantioselective conjugate addition methods, based on the use of organometallic reagents or ground-state iminium ion activation, could not provide general and efficient solutions. We report herein that, by turning them into strong oxidants, visible light excitation of chiral iminium ions triggers a stereocontrolled radical pathway that exclusively affords highly enantioenriched β-substituted aldehydes bearing a variety of alkyl fragments