Metal-Free and Regioselective Synthesis of Substituted and Fused Chromenopyrrole Scaffolds via the Divergent Reactivity of α-Azido Ketones in Water.

A green and simple approach was developed for the regioselective synthesis of structurally diverse chromenopyrrole frameworks from 3-formylchromones, active methylenes, and α-azido ketones using piperidine as a catalyst in the aqueous medium through a tandem one-pot multicomponent reaction. Further, the synthesized pyrrole framework was successfully converted into biologically significant 6-azaindole derivatives in a simple synthetic transformation. An exciting feature of this synthetic protocol is that the reaction mechanism and formation of the products depend on the nature of the active methylene used. This approach has several advantages such as a transition-metal-free catalyst, a short reaction time, easy separation, an excellent yield, practically simple execution, high regioselectivity, very good atom economy, low E-factor, and no requirement of toxic solvents and chromatographic purification.

4-(4-Bromo-phen-yl)-7,7-dimethyl-2-methyl-amino-3-nitro-7,8-di-hydro-4H-chromen-5(6H)-one including an unknown solvate.

In the title compound, C18H19BrN2O4, the chromene unit is not quite planar (r.m.s. deviation = 0.199 Å), with the methyl C atoms lying 0.027 (4) and 1.929 (4) Šfrom the mean plane of the chromene unit. The six-membered carbocyclic ring of the chromene moiety adopts an envelope conformation, with the dimethyl-substituted C atom as the flap. The methyl-amine and nitro groups are slightly twisted from the chromene moiety, with C-N-C-O and O-N-C-C torsion angles of 2.7 (4) and -0.4 (4)°, respectively. The dihedral angle between the mean plane of the chromene unit and the benzene ring is 85.61 (13)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif, which stabilizes the mol-ecular conformation. In the crystal, mol-ecules are linked via N-H⋯O hydrogen bonds, forming hexa-gonal rings lying parallel to the ab plane. A region of disordered electron density, most probably disordered ethanol solvent mol-ecules, occupying voids of ca 432 Å(3) for an electron count of 158, was treated using the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. Their formula mass and unit-cell characteristics were not taken into account during refinement.

Crystal structure of 4-(4-meth-oxy-phen-yl)-7,7-dimethyl-2-methyl-amino-3-nitro-7,8-di-hydro-4H-chromen-5(6H)-one.

In the title compound, C19H22N2O5, the six-membered carbocyclic ring of the chromene moiety adopts an envelope conformation with the dimethyl-substituted C atom as the flap. The pyran ring has a flat-boat conformation. The meth-oxy-phenyl ring is orthogonal to the mean plane of the chromene moiety, with a dihedral angle of 89.97 (8)°. The amine N atom deviates from the chromene mean plane by 0.1897 (16) Å. The methyl-amine and the nitro group are involved in an intra-molecular N-H⋯O hydrogen bond which generates an S(6) ring motif. They are slightly twisted out of the plane of the chromene moiety with torsion angles of C-N-C-O(pyran) = 2.2 (3)° and O(nitro)-N-C-C = -5.6 (2)°. In the crystal, there are only C-H⋯π inter-actions present, forming inversion-related dimers.

7,7-Dimethyl-2-methyl-amino-4-(4-methyl-phenyl)-3-nitro-7,8-di-hydro-4H-chromen-5(6H)-one.

In the title compound, C19H22N2O4, the six-membered cyclo-hexenone ring of the chromene unit adopts an envelope conformation, with the dimethyl-substituted C atom as the flap, while the pyran ring has a boat conformation. These two mean planes are inclined to one another by 6.65 (13)°·The benzene ring is normal to the 4H-chromene moiety mean plane, making a dihedral angle of 89.18 (5)°. The methyl-amine and nitro groups are slightly twisted from the chromene moiety mean plane, with torsion angles C-N-C-O = 1.70 (18) and O-N-C-C = 0.15 (18)°. The mol-ecular structure is characterized by an intra-molecular N-H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked via pairs of weak C-H⋯O hydrogen bonds, forming inversion dimers. These dimers are connected by further C-H⋯O hydrogen bonds, forming sheets lying parallel to (10-1).

4-(4-Bromo-phen-yl)-2-methyl-amino-3-nitro-5,6,7,8-tetra-hydro-4H-chromen-5-one.

In the title compound, C16H15BrN2O4, the six-membered carbocyclic ring of the chromene moiety adopts an envelope conformation with the disordered methyl-ene C atom as the flap. The pyran ring is almost orthogonal to the chloro-phenyl ring, making a dihedral angle of 87.11 (12)°. The amine-group N atom deviates significantly from the pyran ring [0.238 (3) Å]. The mol-ecular structure is stabilized by an intra-molecular N-H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, which generate C(8) chains running parallel to the b axis. The chains are linked by C-H⋯π inter-actions. The methyl-ene-group C atom of the chromene system that is disordered, along with its attached H atoms and the H atoms on the two adjacent C atoms, has an occupancy ratio of 0.791 (7):0.209 (7).

(4S*)-2-Methyl-amino-3-nitro-4-(4-nitro-phen-yl)-5,6,7,8-tetra-hydro-4H-chromen-5-one.

The title compound, C16H15N3O6, is asymmetric with a chiral centre located in the pyran ring and crystallizes as a racemate. The six-membered carbocyclic ring adopts an envelope conformation with the central CH2 C atom as the flap. The amine N atom deviates from the mean plane of the pyran ring by 0.1365 (15) Å. The nitro-phenyl ring is almost orthogonal to the pyran ring and the mean plane of the six-membered carbocyclic ring, the dihedral angle between their mean planes being 88.30 (7) and 87.61 (8)°, respectively. The mol-ecular structure is stabilized by an intra-molecular N-H⋯O hydrogen bond, which generates an S(6) ring motif. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming infinite bands lying parallel to (-110) and composed of alternate R 2 (2)(24) and R 2 (4)(12) graph-set ring motifs. The crystal structure is further stabilized by C-H⋯π inter-actions, forming a three-dimensional structure.

2-Amino-6-(piperidin-1-yl)-4-p-tolyl-pyridine-3,5-dicarbo-nitrile.

In the title compound, C19H19N5, the piperidine ring adopts a chair conformation. The pyridine ring is essentially planar, with a maximum deviation of 0.039 (2) Šfor a C atom substituted with a carbonitrile group. The mean plane of the central pyridine ring makes the dihedral angles of 37.90 (14) and 56.10 (12)° with the piperidine and benzene rings, respectively. In the crystal, mol-ecules are linked via N-H⋯N and C-H⋯N hydrogen bonds, forming chains along [101], and enclosing R 2 (2)(17) ring motifs. The chains are linked by further C-H⋯N hydrogen bonds, forming two-dimensional networks lying parallel to (10-1), and enclosing inversion dimers with R 2 (2)(20) ring motifs.

rac-4-(4-Chloro-phen-yl)-2-methyl-amino-3-nitro-5,6,7,8-tetra-hydro-4H-chromen-5-one.

The title compound, C16H15ClN2O4, contains a chiral centre and crystallizes as a racemate. The methyl-ene group ß-positioned to the carbonyl group is partially (21%) disordered. It flips to the opposite sides of the corresponding six-membered carbocycle by -0.304 (3) and 0.197 (11) Å, producing alternative envelope conformations. The planes of the pyran and chloro-phenyl rings form a dihedral angle of 86.25 (9)°. The mol-ecular structure is characterized by an intra-molecular N-H⋯O inter-action, which generates an S(6) ring motif. The corresponding amino N atom deviates from the plane of the pyran ring by 0.1634 (19) Å. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming C(8) chains running parallel to the b-axis direction. The crystal structure also features C-H⋯π inter-actions.

2-Amino-4-(4-chloro-phen-yl)-6-(pyrrolidin-1-yl)pyridine-3,5-dicarbonitrile.

In the title compound, C(17)H(14)ClN(5), two C atoms and their attached H atoms of the pyrrolidine ring are disordered over two sets of sites with an occupancy ratio of 0.638 (10):0.362 (10). The benzene and pyridine rings are inclined to one another by 60.57 (8)°. In the crystal, the amino group forms an N-H⋯N hydrogen bond with one of the cyano groups, linking the mol-ecules into chains along [010].

Acetylene containing 2-(2-hydrazinyl)thiazole derivatives: design, synthesis, and in vitro and in silico evaluation of antimycobacterial activity against Mycobacterium tuberculosis.

Mycobacterium tuberculosis resistance to commercially available drugs is increasing day by day. To address this issue, various strategies were planned and are being implemented. However, there is a need for new drugs and rapid diagnostic methods. For this endeavour, in this paper, we present the synthesis of acetylene containing 2-(2-hydrazinyl) thiazole derivatives and in vitro evaluation against the H37Rv strain of Mycobacterium tuberculosis. Among the developed 26 acetylene containing 2-(2-hydrazinyl) thiazole derivatives, eight compounds inhibited the growth of Mycobacterium tuberculosis with MIC values ranging from 100 µg ml-1 to 50 µg ml-1. The parent acetylene containing thiosemicarbazones showed promising antimycobacterial activity by inhibiting up to 75% of the Mycobacterium at 50 µg ml-1. In addition, in silico studies were employed to understand the binding mode of all the novel acetylene-containing derivatives against the KasA protein of the Mycobacterium. Interestingly, the KasA protein interactions with the compounds were similar to the interactions of KasA protein with thiolactomycin and rifampicin. Cytotoxicity study results indicate that the compounds tested are non-toxic to human embryonic kidney cells.

2-Amino-6-(pyrrolidin-1-yl)-4-p-tolyl-pyridine-3,5-dicarbonitrile.

In the title compound, C(18)H(17)N(5), the pyrrolidine ring adopts an envelope conformation. The pyrrolidine ring is disordered over two sets of sites with occupancy factors of 0.648 (6) and 0.352 (6). The dihedral angles between the pyrrolidine and pyridine rings are 14.6 (3)° for the major component and 16.2 (6)° for the ninor component. The crystal structure is stabilized by inter-molecular N-H⋯N and C-H⋯N inter-actions.

Crystal structure of 2-methyl-amino-3-nitro-4-p-tolyl-pyrano[3,2-c]chromen-5(4H)-one.

In the racemic title compound, C20H16N2O5, the pyran ring adopts a shallow envelope conformation, with the stereogenic C atom displaced from the other atoms by 0.273 (2) Å. The dihedral angle between the fused-ring system and the pendant p-tolyl group is 87.62 (7)°. The mol-ecular conformation is consolidated by an intra-molecular N-H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, mol-ecules are linked by C-H⋯O inter-actions, resulting in [010] chains.