1,3-Dicarbonyl compounds in stereoselective domino and multicomponent reactions

Asymmetric transformations involving 1,2-dicarbonyl compounds as pronucleophiles

This article concentrates on the versatile nucleophilic reactivity of 1,2-dicarbonyl compounds in various asymmetric transformations. Although underexploited in comparison to their 1,3-dicarbonyl homologues, the presence of adjacent multiple reactive centres allows the selection of specific activation modes for enhancing the reactivity of these important ambident pronucleophiles. They can be involved in selective formation of C-C, C-O or C-N bonds leading to various optically active targets in the acyclic and cyclic series including three- to seven-membered ring systems. Recent contributions in the field of biochemical, organometallic and organic catalytic transformations as well as some relevant stoichiometric approaches are discussed from synthetic and mechanistic point of views highlighting some important stereochemical issues.

A microwave-assisted bismuth nitrate-catalyzed unique route toward 1,4-dihydropyridines

The classical Hantzsch reaction is one of the simplest and most economical methods for the synthesis of biologically important and pharmacologically useful 1,4-dihydropyridine derivatives. Bismuth nitrate pentahydrate under microwave irradiation is proven to act as a very efficient catalyst for a one-pot, three-component synthesis of 1,4-dihydropyridines in excellent yields from diverse amines/ammonium acetate, aldehydes and 1,3-dicarbonyl compounds within 1–3 min under solvent-free conditions. The present environmentally benign procedure for the synthesis of 1,4-dihydropyridines is suitable for library synthesis and it will find application in the synthesis of potent biologically active molecules. The excellent yield and extreme rapidity of the method is due to a concurrent effect of the catalyst and microwave irradiation.

Diversity oriented syntheses of conventional heterocycles by smart multi component reactions (MCRs) of the last decade

A collection of smart multicomponent reactions (MCRs) with continuative post condensation cyclizations (PCCs) is presented to construct conventional three- to seven-membered heterocyclic compounds in diversity oriented syntheses (DOS). These will provide a high degree of applying economical and ecological advantages as well as of practicability. Water, ionic liquids, and solvent-less syntheses as well as use of various forms of energy as microwave and ultrasonic irradiation are examined and discussed.

One-pot four-component synthesis of pyrimidyl and pyrazolyl substituted azulenes by glyoxylation-decarbonylative alkynylation-cyclocondensation sequences

A novel one-pot four-component synthesis of pyrimidyl- and pyrazolylazulenes through the use of glyoxylation-decarbonylative alkynylation-cyclocondensation sequences starting from azulene or guaiazulene as substrates, gives rise to the formation of the target compounds in moderate to good yields.

Synthesis of functionalized 2-aminohydropyridines and 2-pyridinones via domino reactions of arylamines, methyl propiolate, aromatic aldehydes, and substituted acetonitriles

An efficient and practical synthetic method for the functionalized 2-amino hydropyridines and 2-pyridinones was successfully developed via the domino reactions of arylamines, methyl propiolate, aromatic aldehydes and the substituted acetonitriles with triethylamine as base catalyst. Reactions involving malononitrile and cyanoacetamide gave exclusively the 2-aminohydropyridines. On the other hand ethyl cyanoacetate resulted in the 2-pyridinones as main products.

Synthesis of 3,4-dihydropyridin-2(1H)-ones and 3,4-dihydro-2H-pyrans via Four-component reactions of aromatic aldehydes, cyclic 1,3-carbonyls, arylamines, and dimethyl acetylenedicarboxylate

A protocol has been developed for the efficient synthesis of structurally diverse 3,4-dihydropyridin-2(1H)-ones and 3,4-dihydro-2H-pyrans via four-component reactions of arylamines, acetylenedicarboxylate, aromatic aldehydes and cyclic 1,3-diketones. The selective formation of the very different pyridinone or pyran derivatives depends on the structure of cyclic 1,3-diketone. The key steps are proposed to involve Michael addition of the enamino ester formed in situ from the reaction of arylamine with dimethyl acetylenedicarboxylate to arylidine cyclic 1,3-diketones.

Highly diastereo- and enantioselective organocatalytic michael addition of α-ketoamides to nitroalkenes

The first organocatalytic enantio- and diastereoselective conjugate addition of α-ketoamides to nitroalkenes has been achieved using a bifunctional amino thiourea catalyst. In this new approach, the substrate amide proton plays a critical role in the formation of the Michael anti-adducts in high yields and high stereoselectivities. To illustrate the high synthetic potential of this methodology, the diastereo- and enantioselective synthesis of a hexasubstituted cyclohexane via a Michael-Michael-Henry cascade reaction is described.