Calcium chloride with one drop of conc. HCl was found facile and efficient catalyst for the synthesis of aryl 14H-dibenzo[a,j] xanthenes via one-pot condensation of  various substituted benzaldehydes and β-naphthol under microwave and solvent-free conditions. The present protocol offers several advantages such as shorter reaction time, good to excellent yields, simple to operate, inexpensive and easily available catalyst.

Riolozatrione is a natural diterpene isolated form Jatropha dioica to which anti-viral activity is attributed. In this work we report the synthesis of 5 new derivatives and its anti-herpetic evaluation. Riolozatrione posses a unique diterpene core attractive for chemical modification. Conjugate ketone was selectively hydrogenated whereas sodium borohydride draws for three different riolozatrione analogues. 

Nanoporous heterogeneous catalysts have been applied in many reactions due to the high contact area and orderly porous structures with thermal, chemical and mechanical stability [1]. Pyrroles and their derivatives are one of the most important classes of heterocyclic compounds [2]. A four-component coupling reaction (4cr) consisted of aldehydes 1, amines 2, 1, 3 -dicarbonyl compounds 3 and nitromethane 4 afforded substituted pyrroles 5, using MCM-41-SO3H as heterogeneous catalyst. We investigated the synthesis of pyrrole derivatives in the solvent-free conditions. Products were obtained in good yields and short times.

4a-Methyl-2,3,3,4a-tetrahydro-1H-carbazole (3), obtained from phenylhydrazinium chloride and 2-methylcyclohexanone, was regioselectively reduced with sodium borohydride to 4a-methyl-2,3,4,4a,9a-hexahydro-1H-carbazole (4).

Cyclocondensation of hexahydrocarbazole 4 with 2 molecules of diethyl malonate 5a gives 7-hydroxy-13a-methyl-9a,10,11,12,13,13a-hexahydro-5H,8H-pyrano[2',3':4,5] pyrido[3,2,1-jk]carbazole-5,8-dione (6), which affords in a 2-step degradation 5-unsubstituted 4-hydroxy-11a-methyl-7a,8,9,10,11,11a-hexahydro-6H-pyrido[3,2,1-jk]carbazol-6-one (9). Nitration of 9 forms the 5-nitro compound 12, which cyclized after chlorination and azidation at position 4 on thermolysis to the 12a-methyl-7-oxo-8a,9,10,11,12,12a-hexahydro-7H-[1,2,5]oxadiazolo[3',4':4,5]pyrido[3,2,1-jk] carbazol-6-oxide 15.

Cyclocondensation of hexahydrocarbazole 4 with phenylmalonate 5b forms 4-hydroxy-11a-methyl-5-phenyl-7a,8,9,10,11,11a-hexahydro-6H-pyrido[3,2,1-jk]carbazol-6-one (16a), which cyclized after chlorination and azidation at position 4 on thermolysis to the 3b-methyl-3b,4,5,6,7,7a-hexahydroindolo[2',3':4,5]pyrido[3,2,1-jk]carbazol-9(14H)-one derivative 19. The conditions in the thermolytical decomposition and cyclization of the azido compounds were investigated by differential thermal analysis (DSC).

Naphthoquinones are natural pigments that widely distributed in nature and have important biological activities. Lawsone (2-hydroxy-1,4-naphthoquinone) and its synthetic derivatives, and especially those containing nitrogen, have promising potential for the treatment of different diseases due to their antibacterial, antifungal, antiviral, antitumor and antiparasitic effects [1].

     The Mannich reaction is one of the most widely used three component reactions which utilizes a non-enolizable aldehyde, a primary or secondary amine and an enolizable carbonyl compound resulting -amino carbonyl compounds [2]. In this work, we used carboxymethyl cellulose (CMC) as heterogeneous catalyst for multicomponent mannich reaction. CMC is a cellulose derivative with carboxymethyl groups, it is widely used, and inexpensive, biodegradable.

     Synthesis of 2-hydroxy-1,4- naphtoquinone derivatives were performed by simple reaction between 2-hydroxy-1,4- naphtoquinone, aromatic aldehydes and amines in the presence of CMC. The advantages of this procedure are excellent yields within short times, green catalyst and mild reaction conditions.

Our research group was focused on the synthesis of a novel library of thiazolo[5,4-f]quinazolines  and thiazolo[5,4-f]quinazolin-9(8H)-one as potential kinase inhibitors involved to some extent in Alzheimer's disease.¹ We previously reported that 4-N-alkylated/arylated thiazolo[5,4-f]quinazolines displayed single-digit nanomolar IC₅₀ values and are among the most potent DYRK1A/1B inhibitors disclosed to date.² Following our effort for the construction of a broad range of substituted thiazoloquinazolin-4-one derivatives,³ the synthesis of an array of C2 and/or C7 arylated compounds was further envisioned. In this context, transition-metal-catalyzed C-C coupling of heteroarene through C-H arylation represents an extremely attractive approach.⁴ This methodology has emerged as an important tool for incorporating structural diversity into complex nitrogen containing heterocycles, without the need for prefunctionalized starting materials, useful in drug discovery.

Following our previous study on C-H arylation of quinazolinone skeleton,⁵ a selective palladium-catalyzed and copper-assisted direct C-H (hetero)-arylation of thiazolo[5,4-f]quinazolin-9(8H)-one has been developed with aryl iodides and bromides as coupling partners under microwave irradiation.⁶ This innovative sequential C-H functionalization tolerates a broad range of heteroaryl and aryl halides substituted by electronically different groups.⁷ Differently substituted N⁸-benzylated-2,7-diaryl-thiazoloquinazolin-9(8H)-ones were thereby obtained in a facile manner. A one-pot procedure has also been performed. b-bromostyrene was also an effective coupling partner as demonstrated by the alkenylation reaction leading exclusively to the corresponding (E)-isomer. These protocols provide a synthetically useful route for late-stage functionalization of this high valuable scaffold, required in drug discovery.

References

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A new ligand H₃L, with internal compartments for allocating 3d metal ions and external donors to bind 4f ions, was synthesized and completely characterized. Reaction of H₃L with zinc(II) and gadolin ium(III) salts allows isolating the heteronuclear complex {[ZnGd(HL)(NO₃)(OAc)(CH₃OH)](NO₃)}∙6H₂O (1·6H₂O). The ability of 1·6H₂O to act as a magnetic resonance imaging (MRI) contrast agent was evaluated and this study shows that both the transversal and longitudinal relaxivities are quite high but the T₁/T₂ ratio of 7.9 indicates that it could have even greater potential as a T₂ contrast agent.

1,3–dipolar cycloaddition reactions are the ones which have been widely used for  many years in the synthesis of five–membered heterocyclic compounds, take an important place in organic chemistry. Even though they are very useful, they have been used in the synthesis of significant natural products since early 1980s. In this study, we examined intramolecular synthesis of tricyclic products with the Click Reaction mechanisms, theoretically. The use of azide substituted five and six membered cyclic starting materials and provided obtaining heterotricyclic compounds in one step. Derivatization was performed by changing the ring size (m) and varying substitüent (R). The reaction coordinates for all reactions were formed upon  finding intermediates and transition states.

In this study, a series of eight 1-[(2-nitrophenyl)carbamoyl]naphthalen-2-yl alkylcarbamates was prepared and characterized. The discussed compounds were prepared by microwave-assisted and conventional synthesis. The compounds were tested for their activity related to inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. The PET-inhibiting activity of the compounds was relatively low; the corresponding IC₅₀ values ranged from 0.233 to 0.487 mmol/L and the highest activity within the series of compounds was observed for 1-[(2-nitrophenyl)carbamoyl]naphthalen-2-yl pentylcarbamate. The compounds were found to inhibit PET in photosystem II.

Synthetic flavylium salts possess the same basic structure as anthocyanins and their color and physical-chemical properties are notably dependent on the nature and position of the functional groups attached to the skeleton. Influence of position C-4 is very dominant in the stabilization of these molecules and the presence of substituent at that position is highly desirable for a food colorant because it would be stable over a wide range of pH values. Flavylium salts substituted at 4-position with bulky hydroxyphenyl substituents were synthesized by acidic condensation according to a slightly modified procedure described by Robinson and Walker. Their thermodynamic properties and conformational analysis have been studied at DFT level.