Search

This review covers the addition of diazo compounds to ketones to afford homologated ketones, either in the presence or in the absence of promoters or catalysts. Reactions with diazoalkanes, aryldiazomethanes, trimethylsilyldiazomethane, α-diazo esters, and disubstituted diazo compounds are covered, commenting on the complex regiochemistry of the reaction and the nature of the catalysts and promoters. The recent reports on the enantioselective version of ketone homologation reactions are gathered in one section, followed by reports on the use of cyclic ketones ring expansion in total synthesis. Although the first reports of this reaction appeared in the literature almost one century ago, the recent achievements, in particular, for the asymmetric version, forecast the development of new breakthroughs in the synthetically valuable field of diazo chemistry.

Herein we show that the 3-hydroxyquinolin-2(1H)-one (3HQ) core is a suitable platform to develop new compounds with anticancer activity against MCF-7 (IC50 up to 4.82 μM) and NCI–H460 (IC50 up to 1.8 μM) cancer cell lines. The ring-expansion reaction of isatins with diazo esters catalysed by di-rhodium (II) complexes proved to be a simple and effective strategy to synthesize 4-carboxylate-3HQs (yields up to 92%). 4-Carboxamide-3HQs were more efficiently prepared using NHS-diazoacetate in yields up to 88%. This innovative methodology enabled the construction of “peptidic-like” 3HQs, with several amino acid substituents. Among this series, the L-leucine derivative induced the cell death of MCF-7 (IC50 of 15.1 μM) and NCI–H460 (IC50 of 2.7 μM) cancer cell lines without causing any appreciable cytotoxicity against the non-cancer cell model (CHOK1).

We present here the NHC-dirhodium(II)/DBU-catalyzed ring expansion reaction of isatins with ethyl diazoacetate. This new one-pot protocol yields the ethyl 3-hydroxy-2(1H)-oxoquinoline-4-carboxylate core, regioselectively and in good to excellent yields. A DFT mechanistic study indicates metallocarbene formation between the 3-hydroxyindole-diazo intermediate and the dirhodium(II) complex to be the rate-limiting step of the reaction. The synthesized ethyl 3-hydroxy-2(1H)-oxoquinoline-4-carboxylate core could be readily converted to viridicatin alkaloids, in yields up to 80 % by a microwave-assisted Suzuki–Miyaura cross coupling of the 3-hydroxy-4-bromoquinolin-2(1H)-one with arylboronic acid.

This review covers the addition of diazo compounds to ketones to afford homologated ketones, either in the presence or in the absence of promoters or catalysts. Reactions with diazoalkanes, aryldiazomethanes, trimethylsilyldiazomethane, α-diazo esters, and disubstituted diazo compounds are covered, commenting on the complex regiochemistry of the reaction and the nature of the catalysts and promoters. The recent reports on the enantioselective version of ketone homologation reactions are gathered in one section, followed by reports on the use of cyclic ketones ring expansion in total synthesis. Although the first reports of this reaction appeared in the literature almost one century ago, the recent achievements, in particular, for the asymmetric version, forecast the development of new breakthroughs in the synthetically valuable field of diazo chemistry.

A protocol for the preparation of Petasis borono-Mannich products suitable for advanced organic chemistry experiments, using water as a reaction medium, was developed. The experiment is carried out in less than 4 h (with a 30 min pre-session on the day before) using commercially available starting materials in the preparation of phenylglycine and 2-hydroxymorpholine derivatives. These experiments are useful in the organic chemistry curriculum for the introduction of multicomponent reactions and for the use of boronic acids and water as environmentally friendly reagents and solvent, respectively.

A sequential process for the Eistert ring expansion of isatins with ethyl diazoacetate is developed consisting of a DBU-promoted addition of the diazoester to the isatin 3-carboxy group followed by Rh(II)-catalyzed diazo decomposition of the isatin diazo intermediate.