Active Methylene-based Multicomponent Reactions under Microwave Heating

The use of emerging multicomponent reactions (MCRs) in conjunction with microwave (MW)-assisted chemistry techniques is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. MW-assisted active methylene-based multicomponent reactions serve as a rapid and efficient tool for the synthesis of versatile heterocycles, particularly those containing structural diversity and complexity via a one-pot operation. This minireview covers our recent advances on multicomponent reactions involving active methylene compounds for the construction of bioactive molecule skeletons. In many cases, MW-assisted MCRs offer considerable improvements in selectivity, chemical yield and purity and constitutes a very simple and extremely rapid method to access a diverse range of heterocyclic motifs

3-(4-Chloro­phen­yl)-1-(4-nitro­phen­yl)benzo[f]quinoline

In the title compound, C25H15ClN2O2, the pyridine ring is inclined at angles of 6.89 (7), 4.24 (9) and 66.98 (4)° with respect to the naphthalene, chloro­phenyl and nitro­phenyl rings, respectively. The two substituent aromatic rings make a dihedral angle of 71.1 (1)° with one another. C—H⋯π and π–π stacking are present in the crystal structure; the π–π stacking [centroid–centroid distance between the pyridyl rings of adjacent mol­ecules= 3.7838 (11) Å] links the mol­ecules into dimers, while the C—H⋯Cg type π–ring inter­actons link the mol­ecules into a chain structure along c

N-Cyclo­hexyl-3-(4-hydr­oxy-6-oxo-1,6-dihydro­pyrimidin-5-yl)-3-p-tolyl­propanamide

In the mol­ecule of the title compound, C20H25N3O3, the aromatic rings are oriented at a dihedral angle of 88.36 (3)°. The cyclo­hexane ring adopts a chair conformation. In the crystal structure, inter­molecular N—H⋯O and O—H⋯N hydrogen bonds link the mol­ecules. C—H⋯π inter­actions are also present

2-Amino-4-(4-bromo­phen­yl)-6-ferro­cenyl­pyridine-3-carbonitrile

The title compound, [Fe(C5H5)(C17H11BrN3)], was synthesized by the reaction of 4-bromo­benzaldehyde, acetyl­ferrocene and ammonium acetate in an aqueous medium. The crystal packing is stabilized by inter­molecular N—H⋯N hydrogen bonds. The dihedral angles between the phenyl ring and the pyridine and cyclopentadienyl rings are 51.67 (13) and 12.12 (21)°, respectively

2,2,7,7-Tetra­methyl-1,2,3,6,7,8-hexa­hydro­cinnolino[5,4,3-cde]cinnoline

The asymmetric unit of the title compound, C16H20N4, contains two half-mol­ecules, which are completed by crystallographic inversion symmetry. The pyridazine rings are conjugated and the cyclo­hexane rings adopt envelope conformations

(E)-2-(4-Nitro­benzyl­ideneamino)benzamide

The title compound, C14H11N3O3, adopts an E conformation, with a dihedral angle of 41.8 (1) ° between the mean planes of the two benzene rings. One of the amino H atoms forms an intra­molecular hydrogen bond with the amide N atom, while the other H atom forms an inter­molecular hydrogen bond with the carbonyl O atom of an adjacent mol­ecule, forming dimers about inversion centers. A non-classical inter­molecular C—H⋯O hydrogen bond also links adjacent mol­ecules into dimers

4,4′-Dianilino-3,3′-(4-chloro­benzyl­idene)bis­[furan-2(5H)-one]

In the mol­ecule of the title compound, C27H21ClN2O4, the dihedral angle between the furan rings is 67.00 (3)°. The chloro­phenyl ring is oriented at dihedral angles of 76.61 (3) and 69.36 (3)° with respect to the furan rings. An intra­molecular N—H⋯O inter­action results in the formation of an eight-membered ring with a twisted conformation. In the crystal structure, inter­molecular N—H⋯O and C—H⋯O inter­actions link the mol­ecules into a three-dimensional network, forming R 2 2(16) ring motifs. Three weak C—H⋯π inter­actions are also found

N-Cyclo­pentyl-3-(4-hydr­oxy-6-oxo-1,6-dihydro­pyrimidin-5-yl)-3-p-tolyl­propanamide

In the mol­ecule of the title compound, C19H23N3O3, the six-membered rings are oriented at a dihedral angle of 73.06 (3)°. The cyclo­pentyl ring adopts an envelope conformation. In the crystal structure, inter­molecular N—H⋯O and O—H⋯N hydrogen bonds link the mol­ecules. In the tolyl ring, the H atoms and all but one of the C atoms are disordered over two positions and were refined with occupancies of 0.51 (3) and 0.49 (3)