Solid-state Melt Reaction Research Articles

A one-pot, multicomponent tandem synthesis of fused polycyclic pyrrolo[3,2-c]quinolinone/pyrrolizino[2,3-c]quinolinone hybrid heterocycles via environmentally benign solid state melt reaction

Abstract Structurally diverse fused polycyclic pyrrolo[3,2-c]quinolinone/pyrrolizino[2,3-c]quinolinone hybrids were synthesized to get excellent yields via a tandem multi-component reaction sequence employing an environmentally benign solid state melt reaction involving [3+2]-cycloaddition process followed by two consecutive annulation steps. Baylis–Hillman products, used as dipolarophiles, were synthesized from various substituted aryl/heteroaryl aldehydes in the presence of DABCO and methyl acrylate, while the 1,3-dipole component was derived in situ from indoline-2,3-dione and acyclic/cyclic amino acid viz N-methylgylcine/l-proline. The structure of the unusual tandem products was unambiguously assigned by spectroscopic and XRD analysis. The products arose through the formation of three new rings, five new bonds, and three adjoining stereocenters with complete diastereomeric control.

Eco-friendly synthesis and structural determination of pyrene fused pyrroloquinolinone hybrid

Synthesis of a structurally complex hitherto unexplored novel class of pyrene fused pyrroloquinolinone was achieved in excellent yield via an environmental friendly solid-state melt reaction condition employing multicomponent cascade protocol which involves 1,3-dipolar cycloaddition and subsequent double annulation process. The 1,3-dipole component was derived in situ from diketone and α-amino acid, whereas the Baylis-Hillman adduct synthesized from pyrene-1-carbaldehyde was utilized as a dipolarophile. Structure of the compound was elucidated by 1H and 13C NMR spectroscopic analysis and further confirmed through single crystal X-ray diffraction and the molecular packing was described by using Hirshfeld surface analysis. The structure-reactivity descriptors of the synthesized compound were examined through DFT calculations. The pyrroloquinoline was evaluated for its antibacterial activity against three multi drug resistant bacterial and two fungal pathogens. The MIC value of the tested microbial pathogens were exhibited with minimum (0.156 mg/mL) and maximum (1.250 mg/mL). The antimicrobial results disclosed that compound 6 is considered as a potent candidate for effective therapeutic applications.

Environmentally friendly domino multicomponent strategy for the synthesis of pyrroloquinolinone hybrid heterocycles.

An efficient and elegant assembly of pyrene/aryl fused pyrrolo[2,3-b]quinolinone and pyrrolizino[3,2-b]quinolinone hybrid heterocycles was achieved via a domino multicomponent reaction strategy using a solid state melt reaction (SSMR) condition. The 1,3-dipole component was generated in situ from N-methylgylcine/l-proline and isatin, while the Baylis–Hillman adduct prepared from pyrene-1-carbaldehyde and various benzaldehydes is used as the dipolarophile. The domino protocol comprises 1,3-dipolar cycloaddition and a consequent double annulation reaction process. The advantages of this cascade protocol include environmentally friendly conditions, the avoidance of toxic organic solvents, simple work-up and good to excellent product yields.

Effective methods for the synthesis of hydrazones, quinazolines, and Schiff bases: reaction monitoring using a chemometric approach.

Synthesis of hydrazones (1a–4a and 1b–4b), quinazolines (3c·MeOH and 3d·MeOH), and hydrazone-Schiff bases (4c and 4d) is achieved by combining suitable aldehydes (2,3- or 2,4-dihydroxybenzaldehyde) with four hydrazides (isonicotinic, nicotinic, and 2- or 4-aminobenzoic acid hydrazide). A suite of approaches for their preparation is described: solution-based synthesis, mechanosynthesis, and solid-state melt reactions. The mechanochemical approach is generally a better choice for the quinazolines, while the solid-state melt reaction is more efficient for derivatives of (iso)nicotinic based hydrazones. Crystalline amine-functionalised hydrazones 4a and 4b undergo post-synthetic modifications in reactions with 3- or 4-pyridinecarbaldehyde vapours to form hydrazone-Schiff bases 4a-3py, 4b-3py, 4a-4py, and 4b-4py. Mechanochemical and vapour-mediated reactions are followed by ex situ powder X-ray diffraction and IR-ATR methods, respectively. The chemometric analysis of these data using principal component analysis provided an insight into the reaction profiles and reaction times. Azines (5a and 5b), achieved from aldehydes and hydrazine, reversibly change colour in response to temperature changes. The structures of all products are ascertained by a combined use of spectroscopic and X-ray diffraction methods. The cytotoxic and antimicrobial activities of all compounds against selected human cancer cell lines and bacterial strains are evaluated.

Two step, one-pot sequential synthesis of functionalized hybrid polyheterocyclic scaffolds via a solid state melt reaction (SSMR).

A new one pot assembly of highly functionalized benzo[a]phenazinone fused chromene/bicyclic scaffolds via a domino Knoevenagel intramolecular hetero-Diels–Alder (IMHDA) strategy using a solid state melt reaction (SSMR) of 2-hydroxynaphthalene 1,4-dione, o-phenylenediamine, O-allyl salicylaldehyde/O-vinyl salicylaldehyde derivatives is reported. The formation of five new bonds (two C–C bonds and three C–O bonds), three six-membered rings, and three stereogenic centers in a one-pot manner is very attractive. Ease of reaction with short time, good yields with water as the only byproduct and work up free procedure are some of the excellent features of the present protocol.

A rearrangement involving a solid-state melt reaction for the synthesis of multifunctional tetrasubstituted olefins.

A catalyst- and solvent-free intramolecular rearrangement sequence leading towards benzimidazole-tethered tetrasubstituted olefins through a solid-state melt reaction (SSMR) involving imine formation, cyclization, N-allylation and isomerization has been realized for the first time. Interestingly, only water is the byproduct in this novel quadruple domino reaction. Furthermore, the reaction is highly stereoselective, atom economical and environmentally benign in nature.

Mechanistic study of reversible solid-state melt isomerization of 2-oxindoles to 2-quinolinones and its occurrence in a mass spectrometer

An eco-friendly equilibrated rearrangement of a series of 2-oxo-3-indolyl acetic acids (1) with 2-oxo-1,2,3,4-tetrahydroquinoline-4-carboxylic acid derivatives (2) was investigated through a solid state melt reaction (SSMR). Mechanistic insight into the thermal rearrangement is provided by 13C-isotopic labeling. The standard mass spectra of 1 and 2 were virtually identical preventing their reliable identification. Reversible interconversion of 1 and 2 was evidenced to occur in the inlet system of a mass spectrometer under electron impact conditions. Relative abundances of fragment ions were found to be a function of temperature.

A robust synthesis of functionalized 2H-indazoles via solid state melt reaction (SSMR) and their anti-tubercular activity

A facile and convenient approach has been developed for the synthesis of functionalized indazoles via solid state melt reaction using easily accessible starting materials under catalyst-free conditions. This transformation involves electrocyclization via a conjugated nitrene intermediate obtained under thermal conditions. Further anti-tubercular activity screening of the molecules was undertaken, among the compounds 3a-3x screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv, compound 3u (MIC: 4.20μM) was found to be most active and are superior over existing standard drugs ciprofloxacin and ethambutol. Compounds 3c and 3x were found to equally potent as ethambutol. Among most potent compounds in the series, four compounds (3n, 3o, 3p and 3u) showed lower cytotoxicity which could be promising drug candidates for further development.

ChemInform Abstract: One‐Pot Synthesis of Benzothiazole‐Tethered Chromanones/Coumarins via Claisen Rearrangement Using the Solid State Melt Reaction.

A novel protocol has been successfully established for the efficient synthesis of benzothiazole-tethered chromanone/coumarin scaffolds via Claisen rearrangement using a solid state melt reaction in a one-pot manner. Benzothiazole formation and Claisen rearrangement involve the cleavage of S–S and C–O bonds and formation of C–S, C═N, and C–C bonds in a single operation without using a catalyst or solvent.

One-Pot Synthesis of Benzothiazole-Tethered Chromanones/Coumarins via Claisen Rearrangement Using the Solid State Melt Reaction.

A novel protocol has been successfully established for the efficient synthesis of benzothiazole-tethered chromanone/coumarin scaffolds via Claisen rearrangement using a solid state melt reaction in a one-pot manner. Benzothiazole formation and Claisen rearrangement involve the cleavage of S-S and C-O bonds and formation of C-S, C═N, and C-C bonds in a single operation without using a catalyst or solvent.

Eco-friendly construction of highly functionalized chromenopyridinones by an organocatalyzed solid-state melt reaction and their optical properties

Diverse chromenopyridinone derivatives were synthesized under organocatalytic solid-state melt conditions. The optical properties of these π-expanded chromenopyridine derivatives were examined.

ChemInform Abstract: Stereoselective Construction of Functionalized Tetracyclic and Pentacyclic Coumarinopyranpyrazole/Pyrimidinedione/Coumarin Scaffolds Using a Solid‐State Melt Reaction.

AbstractA simple and novel protocol for the facile synthesis of complex angularly substituted tetracyclic and pentacyclic hybrid molecular frameworks containing a coumarinopyranpyrazole/pyrimidinedione and coumarin ring systems via a solid‐state melt reaction (SSMR) through a domino process is developed.

Stereoselective construction of functionalized tetracyclic and pentacyclic coumarinopyranpyrazole/pyrimidinedione/coumarin scaffolds using a solid-state melt reaction.

An assembly of tetra / pentacyclic hybrid scaffolds have been synthesized for the first time using a solid-state melt reaction in a stereoselective fashion with excellent yields.

ChemInform Abstract: A Novel Synthesis of Tetra and Pentacyclic Quinolinopyran Tethered Pyrazole/Coumarin Scaffolds via a Solid State Melt Reaction.

AbstractTitle structures [e.g. (III), (V), (VII), and (VIII)] are efficiently synthesized via domino Knoevenagel intramolecular hetero‐Diels—Alder strategy in a highly diastereo and regioselective fashion.

An efficient protocol for the synthesis of benzoheterocyclic compounds via solid-state melt reaction (SSMR)

An efficient protocol for the synthesis of biologically active benzoheterocyclic compounds such as benzothiazoles, benzimidazoles, benzospirothiazoles, and quinoxaline scaffolds have been accomplished via solid state melt reaction (SSMR) with excellent yields. The new protocol does not require any catalyst, solvent, and workup. Two anti-tumor agents have been prepared to demonstrate the application of this new method.

ChemInform Abstract: Highly Stereo‐ and Chemoselective Synthesis of Tetra and Pentacyclic Frameworks Using Solid‐State Melt Reaction (SSMR).

Abstract Benzopyran fused tetra and pentacyclic frameworks have been synthesized by the domino Knoevenagel hetero Diels–Alder (DKHDA) reaction using various 1,3-diones with O-allylated salicylaldehydes and O-propargylated salicylaldehydes in a solvent and catalyst free condition via Solid-State Melt Reaction (SSMR). The reaction requires only a single step operation thus providing potentially bioactive polycyclic heterocycles in high yields.

Highly stereo and chemoselective synthesis of tetra and pentacyclic frameworks using Solid-State Melt Reaction (SSMR)

Benzopyran fused tetra and pentacyclic frameworks have been synthesized by the domino Knoevenagel hetero Diels–Alder (DKHDA) reaction using various 1,3-diones with O-allylated salicylaldehydes and O-propargylated salicylaldehydes in a solvent and catalyst free condition via Solid-State Melt Reaction (SSMR). The reaction requires only a single step operation thus providing potentially bioactive polycyclic heterocycles in high yields.

A novel synthesis of tetra and pentacyclic quinolinopyran tethered pyrazole/coumarin scaffolds via a solid state melt reaction

A new protocol has been developed for the efficient synthesis of structurally diverse tetra- and pentacyclic quinolinopyran tethered pyrazole/coumarin architectures via a domino Knoevenagel intramolecular hetero-Diels–Alder (IMHDA) strategy using a solid state melt reaction (SSMR) in a highly diastereo and regioselective fashion. Gratifyingly, these heterocyclic frameworks were synthesized under solvent and catalyst free conditions, without the aid of a work-up and column chromatography purification. The generality and functional tolerance of this convergent and environmentally benign method is very attractive.

Solid-State Melt Reaction for the Domino Process: Highly Efficient Synthesis of Fused Tetracyclic Chromenopyran Pyrimidinediones Using Baylis−Hillman Derivatives

A solid-state melt reaction (SSMR) has been demonstrated via a domino process for the synthesis of tetracyclic chromenopyran pyrimidinedione frameworks using Baylis-Hillman derivatives through in situ formation of an olefin followed by an intramolecular [4 + 2] cycloaddition reaction sequence. The tetracyclic frameworks were obtained without using catalyst and solvent in a highly stereoselective and stereospecific fashion. The isolated yield is excellent and does not require column chromatography purification to obtain the pure product.

M2(hpp)4Cl2 and M2(hpp)4, where M = Mo and W: preparations, structure and bonding, and comparisons with C2, C2H2, and C2Cl2 and the hypothetical molecules M2(hpp)4(H)2.

The reaction between M(2)Cl(2)(NMe(2))(4), where M = Mo or W, and Hhpp (8 equiv) in a solid-state melt reaction at 150 degrees C yields the compounds M(2)(hpp)(4)Cl(2) 1a (M = Mo) and 1b (M = W), respectively, by the elimination of HNMe(2) [hpp is the anion derived from deprotonation of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp]. Purification of 1a and 1b is achieved by sublimation of the excess Hhpp and subsequent recrystallization from either CH(2)Cl(2) or CHCl(3) (or CDCl(3)). By single-crystal X-ray crystallography, the structures of 1a and 1b are shown to contain a central paddlewheel-like M(2)(hpp)(4) core with Mo-Mo = 2.1708(8) A (from CH(2)Cl(2)), 2.1574(5) A (from CDCl(3)), W-W = 2.2328(2) A (from CDCl(3)), and M-N = 2.09(1) (av) A. The Cl ligands are axially ligated (linear Cl-M-M-Cl) with abnormally long M-Cl bond distances that, in turn, depend on the presence or absence of hydrogen bonding to chloroform. The quadruply bonded compounds M(2)(hpp)(4), 2a (M = Mo), and 2b (M = W), can be prepared from the reactions between 1,2-M(2)R(2)(NMe(2))(4) compounds, where R = (i)()Bu or p-tolyl, and Hhpp (4 equiv) in benzene by ligand replacement and reductive elimination. The compounds 2a and 2b are readily oxidized, and in chloroform they react to form 1a and 1b, respectively. The electronic structure and bonding in the compounds 1a, 1b, 2a, and 2b have been investigated using gradient corrected density functional theory employing Gaussian 98. The bonding in the M-M quadruply bonded compounds, 2a and 2b, reveals M-M delta(2) HOMOs and extensive mixing of M-M pi and nitrogen ligand lone-pair orbitals in a manner qualitatively similar to that of the M(2)(formamidinates)(4). The calculations indicate that in the chloride compounds, 1a and 1b, the HOMO is strongly M-Cl sigma antibonding and weakly M-M sigma bonding in character. Formally there is a M-M triple bond of configuration pi(4)sigma(2), and the LUMO is the M-M delta orbital. An interesting mixing of M-M and M-Cl pi interactions occurs, and an enlightening analogy emerges between these d(4)-d(4) and d(3)-d(3) dinuclear compounds and the bonding in C(2), C(2)H(2), and C(2)Cl(2), which is interrogated herein by simple theoretical calculations together with the potential bonding in axially ligated compounds where strongly covalent M-X bonds are present. The latter were represented by the model compounds M(2)(hpp)(4)(H)(2). On the basis of calculations, we estimate the reactions M(2)(hpp)(4) + X(2) to give M(2)(hpp)(4)X(2) to be enthalpically favorable for X = Cl but not for X = H. These results are discussed in terms of the recent work of Cotton and Murillo and our attempts to prepare parallel-linked oligomers of the type [[bridge]-[M(2)]-](n)().