Jan Bojanowski

In this manuscript, a novel, decarboxylative Michael reaction between α-substituted azlactones and chromone-3-carboxylic acids is described. The reaction proceeds in a sequence Michael addition followed by decarboxylative deprotonation, and it results in the formation of chromanones bearing an azlactone structural unit. The possibility of transforming an azlactone moiety into a protected α,α-disubstituted α-amino acid derivative is also demonstrated.

In the manuscript the first vinylogous, decarboxylative Michael reaction is described. It utilizes 3‐cyano‐4‐methylcoumarins as pronucleophiles undergoing Michael reaction with Michael acceptors activated by the presence of carboxylic acid moiety. Subsequent decarboxylative protonation affords interesting heterocycles in high yields with the reaction realized in the presence of Brønsted base catalyst. Attempts to develop an enantioselective variant of the decarboxylative reaction cascade are also described.

Within the performed study, a dearomatizative and decarboxylative reaction cascade for the synthesis of biologically relevant 3,4‐dihydrocoumarins has been developed. It utilizes 2‐alkyl‐3‐furfural derivatives that under aminocatalytic conditions are transformed into dienamine‐like intermediates in a process that involves dearomatization of the furan ring. Subsequent [4+2]‐cycloaddition with coumarin‐3‐carboxylic acids proceeds with rearomatization of the furan moiety. In the last step of the cascade, the aminocatalyst is released via decarboxylative deamination to give target 3,4‐dihydrocoumarins with excellent enantio‐ and diastereocontrol.

This Minireview summarizes the application of carboxylic‐acid‐activated olefins in organic synthesis. The ability of carboxylic acid moiety to increase the electrophilic character of alkenes combined with the possibility to remove it under mild reaction conditions via decarboxylation process allows for the development of new reactivity patterns. These strategies involve mainly cascade reactions consisting of either Michael addition followed by decarboxylation or cycloaddition followed by decarboxylation. New synthetic possibilities provided by these approaches are summarized and discussed within this review article.

This Communication describes the first decarboxylative trienamine-mediated cycloaddition between 2,4-dienals and coumarin-3-carboxylic acids.

An unprecedented organocatalytic cis-selective aziridination of α,β-unsaturated aldehydes is described. The strategy utilizes postreaction isomerization as a key step. Our study demonstrates that by a proper choice of structural features of reagents and the catalyst the outcome of well-established reactions can be altered, leading to the formation of normally inaccessible diastereomers. The usefulness of the developed approach has been confirmed in the syn-selective formal aminohydroxylation of α,β-unsaturated aldehydes.

A novel decarboxylative aminocatalytic strategy for the synthesis of 4,4a‐dihydroxanthones is described. It was realized by employing dienamine activation and utilizes readily available β,β‐disubstituted enals and chromone‐3‐carboxylic acids as starting materials. A decarboxylation reaction is the key step of the cascade making the aminocatalyst turnover possible. magnified image

In this manuscript, a novel approach to 3,4‐dihydrocoumarins is presented. It utilizes the aminocatalytic, trienamine‐mediated cycloaddition reaction between 2,4‐dienals and ethyl coumarincarboxylates. The reaction is promoted by a bifunctional aminocatalyst bearing a hydrogen‐bonding squaramide structural unit. As a consequence, the stereochemical outcome is governed through the double hydrogen‐bonding interactions between the hydrogen‐bonding moiety of the catalyst and the dienophile. The transformation of the obtained cycloadducts into 3,4‐dihydrocoumarins bearing a bislactone structural motif is presented.