The Michael reaction has been the subject of numerous reviews. Furthermore, the first review on anti-Michael addition has been published. The present review focuses only on the functionalization of indoles and the pyrroles via Michael additions because of the potential biological activity exhibited by these compounds.

Functionalization of Indole and Pyrrole Cores via Michael-Type Additions

The tandem Michael addition/decarboxylation of (thio)coumarin-3-carboxylic acids with indoles has been developed and the biologically important indole-3-substituted dihydrocoumarins were obtained in good to excellent yields under catalyst-free conditions.

Catalyst-free tandem Michael addition/decarboxylation of (thio)coumarin-3-carboxylic acids with indoles: facile synthesis of indole-3-substituted 3,4-dihydro(thio)coumarins

The tandem process of phenol addition to a cyclic α,β-unsaturated ester followed by intramolecular transesterification and [1,5] sigmatropic rearrangement affords a series of helical coumarins base...

Polarized Helical Coumarins: [1,5] Sigmatropic Rearrangement and Excited-State Intramolecular Proton Transfer.

The sequential three-component reaction between o-hydroxybenzaldehydes, N-(cyanomethyl)pyridinium salts and a nucleophile towards substituted chromenoimidazopyridines under oxidative conditions has been developed. The employment of Mn(OAc)3·2H2O or KMnO4 as stoichiometric oxidants allowed the use of a wide range of nucleophiles, such as nitromethane, (aza)indoles, pyrroles, phenols, pyrazole, indazole and diethyl malonate. The formation of the target compounds presumably proceeds through a domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction sequence.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-14-287.pdf

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines.

A mild method for an efficient synthesis of C3-naphthyl indoles from o-alkynylacetophenones has been developed. This Ag-catalyzed transformation is assisted by the acetal formed under the reaction condition employing trimethyl orthoformate (TMOF). The role of acetal in promoting the reaction under ambient conditions has been established with control experiments. A range of C3-naphthyl indole derivatives have been synthesized in moderate to very good yields.

Ag(I)-catalyzed cyclization of o-alkynylacetophenones facilitated through acetal formation: synthesis of C3-naphthyl indole derivatives.

Tandem Michael additions of indole derivatives to 3-nitrocoumarins 2, followed by MVK, in one pot, has been developed for the synthesis of multi-functionalized 3,4-dihydrocoumarins bearing a quaternary stereocenter. The reaction proceeds with high diastereoselectivities in good to excellent yields.

Yao-Yu Yang

Papers

Diastereoselective Tandem Michael Additions of Indoles to 3-Nitrocoumarin Derivatives and Methyl Vinyl Ketone