1,3-Dipolar cycloaddition constitutes powerful means for the synthesis of five-membered heterocycles. Recently, the potential of this field of chemistry has been expanded by the employment of organocatalytic activation strategies. One...

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.[a] J.

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 dienaminelike 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 enantioand diastereocontrol.