Organic photocatalysts are emerging as viable and more sustainable tools than metal complexes. Recently, the field of organo‐photocatalysis has experienced an explosion in terms of applications, ...redesign of well‐established systems, and identification of novel scaffolds. A rational approach to the structural modification of the different photocatalysts is key to accessing unprecedented reactivity, while improving their catalytic performances. We herein discuss the concepts underpinning the scaffold modification of some of the most recently used photocatalysts and analyze how specific structural changes alter their physicochemical and redox properties.
No more trial and error! This Minireview outlines how a careful physicochemical properties analysis is instrumental towards the rational selection of a photocatalyst while delineating future applications and structural evolution.
The Front Cover illustrates methods for the synthesis of thiocarboxylates which play important roles in biologically and pharmaceutically active compounds, providing general ideas for achieving more ...effective thioester drugs. More information can be found in the Review by X. Wang and Z.‐B. Dong.
The first catalytic asymmetric Piancatelli reaction is reported. Catalyzed by a chiral Brønsted acid, the rearrangement of a wide range of furylcarbinols with a series of aniline derivatives provides ...valuable aminocyclopentenones in high yields as well as excellent enantioselectivities and diastereoselectivities. The high value of the aza‐Piancatelli rearrangement was demonstrated by the synthesis of a cyclopentane‐based hNK1 antagonist analogue.
A chiral Brønsted acid catalyzes the asymmetric Piancatelli rearrangement of a wide range of furylcarbinols with aniline derivatives, affording valuable 4‐aminocyclopentenones in high yields and with high enantio‐ and diastereocontrol. Challenging alkyl‐substituted tertiary furylcarbinols gave the corresponding products with a chiral quaternary stereocenter with excellent enantioselectivity.
A novel alkyl functionalization of unactivated alkyl quinolines has been developed combining InCl3 activation with organocatalytic activation of α,β‐unsaturated aldehydes in a synergistic fashion. ...The reaction proceeds in a highly stereoselective manner as a sequence involving two consecutive synergistic catalytic cycles (Lewis acid‐ and iminium ion‐catalyzed) and requires neither pre‐activated alkyl quinoline substrates with electron‐withdrawing substituents nor highly activated electrophiles. The reaction provides selectively double‐ or mono‐addition products in good yields and high to excellent stereoselectivities. Furthermore, based on spectroscopic and labelling experiments, the mechanisms for the reactions are discussed.
A fruitful partnership: InCl3 activation of unactivated alkyl quinolines has been combined with organocatalytic activation of α,β‐unsaturated aldehydes. The reaction involves two consecutive synergistic catalytic cycles and provides selectively double‐ or mono‐addition products in good yields and high to excellent stereoselectivities. Based on spectroscopic and labeling experiments, the reaction mechanisms are discussed.
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A method that facilitates the construction of valuable chiral products exploiting simple high energy intermediates in an atom- and sustainable fashion could prove highly enabling for ...asymmetric synthesis. Free carbenes are one kind of such high energy intermediates and their utilization in catalytic asymmetric reactions is still elusive, due to the existence of severe racemic background reaction. In our pursuit to develop catalytic asymmetric NH insertion reaction of free carbene, a general chiral Brønsted acid-catalyzed enantioselective protonation of the in situ generated ammonium ylide was discovered under visible-light irradiation of diazo compound in the presence of arylamine, furnishing the desired α -amino esters with moderate to high enantioselectivity and yield. More importantly, it was found there is a remarkable correlation between the enantioselectivity of product and substituent electronic parameter (σpara) of substrates. This work not only demonstrates chiral phosphoric acid catalysis is compatible with free carbene insertion reactions without disturbing deactivation OH insertion side reactions, but also indicates the pKa of arylamine is also a significant parameter for turning the enantioselectivity of the reaction. The method disclosed herein is expected to bring new insights into the use of free carbene in the catalytic asymmetric reactions under metal free conditions.
Being direct: A Brønsted acid catalyzed α alkylation of ketones is described. The phosphoric acid 1 promotes this reaction to afford the desired products with high yields, high ...diastereoselectivities, and good to excellent enantioselectivites.
The facile elaboration of optically active α‐sulfanyl‐substituted aldehydes makes their direct preparation from unmodified aldehydes and 1‐benzylsulfanyl‐1,2,4‐triazole particularly valuable. The ...substituted aldehydes are formed with excellent enantioselectivities in the presence of sterically demanding chiral pyrrolidine derivatives as organocatalysts (see scheme). R, R′=H, alkyl, allyl, benzyl, Ph.
