A chemical placebo: NaCl as an effective, cheapest, non-acidic and greener catalyst for Biginelli-type 3,4-dihydropyrimidin-2(1H)-ones (-thiones) synthesis

Efficient Synthesis of Dihydropyrimidines Using a Highly Ordered Mesoporous Functionalized Pyridinium Organosilica

A Brönsted acidic ionic solid pyridinium-functionalized organosilica network (PMO-Py-IL) was demonstrated to efficiently catalyse one-pot Biginelli condensation reaction. The green synthesis of 3,4-dihydro-2(H)-pyrimidinones (DHPMs) with high yield was carried out via one-pot three component condensation of β- dicarbonyls, aldehydes, and urea in the presence of a catalytic amount of PMO-Py-IL nanomaterial as an efficient nanocatalyst under solvent free conditions. Furthermore, the catalyst showed outstanding stability and could be easily separated and reused for at least ten reaction runs without significant loss of activity and product selectivity. The green protocol features simple set-up, cost-effectiveness, easy work-up, eco-friendly and mild reaction conditions.

Advanced Mechanochemistry Device for Sustainable Synthetic Processes

Mechanochemistry is an alternative for sustainable solvent-free processes that has taken the big step to become, in the near future, a useful synthetic method for academia and the fine chemical industry. The apparatus available, based on ball milling systems possessing several optimizable variables, requires too many control and optimization experiments to ensure reproducibility, which has limited its widespread utilization so far. Herein, we describe the development of an automatic mechanochemical single-screw device consisting of an electrical motor, a drill, and a drill chamber. The applicability and versatility of the new device are demonstrated by the implementation of di- and multicomponent chemical reactions with high reproducibility, using mechanical action exclusively. As examples, chalcones, dihydropyrimidinones, dihydropyrimidinethiones, pyrazoline, and porphyrins, were synthesized with high yields. The unprecedented sustainability is demonstrated by comparison of EcoScale and E-factor values of these processes with those previously described in the literature.

1, 1'-Sulfinyldiethylammonium Bis (Hydrogen Sulfate) as a Recyclable Dicationic Ionic Liquid Catalyst for the Efficient Solvent-free Synthesis of 3, 4-Dihydropyrimidin-2(1H)-ones via Biginelli Reaction

OBJECTIVE

A facile and efficient method for synthesis of 3, 4-dihydropyrimidin-2(1H)-ones via Biginelli reaction catalyzed by a novel dicationic Brönsted acidic ionic liquid, [(EtNH2)2SO][HSO4]2, has been successfully developed.

MATERIALS AND METHODS

3, 4-Dihydropyrimidin-2(1H)-ones were synthesized through one-pot condensation of aromatic aldehydes, ethyl acetoacetate, and urea under solvent-free conditions using [(EtNH2)2SO][HSO4]2 as a novel catalyst. The progress of the reaction was monitored by thin-layer chromatography (ethyl acetate / n-hexane = 1 / 5). The products have been characterized by IR, 1H NMR, 13C NMR, and also by their melting points.

RESULTS

In this research, a library of dihydropyrimidinone derivatives was synthesized via Biginelli reaction under solvent-free conditions at 120oC using [(EtNH2)2SO][HSO4]2 as a catalyst. Various aromatic aldehydes, as well as heteroaromatic aldehydes, were employed, affording good to high yields of the corresponding products and illustrating the substrate generality of the present method. In addition, the prepared dicationic Brönsted acidic ionic liquid can be easily recovered and reused.

CONCLUSION

1, 1'-Sulfinyldiethylammonium bis (hydrogen sulfate), as a novel dicationic ionic liquid, can act as a highly efficient catalyst for the synthesis of 3, 4-dihydropyrimidin-2(1H)-ones under solvent-free conditions.

The Effects of Different Catalysts, Substituted Aromatic Aldehydes on One-Pot Three-Component Biginelli Reaction

AIM AND OBJECTIVE

The Biginelli reaction, first reported in 1893, is one great example of the important multicomponent reactions reported from 1893. Under the same conditions, the influence of the common catalysts on the yield of the Biginelli reaction was investigated.

MATERIALS AND METHOD

To a round-bottom flask equipped with a spherical condenser were added 1,3- dicarbonyl compound (1.0 eq), urea (1.45 eq), aromatic aldehyde (1.0 eq), catalyst and methanol. The mixture was heated at reflux for 16 h. After cooling off, the mixture was filtered and washed with cold methanol to give DHPMs. Reaction solution was further purified by recrystallization with petroleum ether and ethyl acetate. Six catalytic systems, different 1,3-dicarbonyl compounds and different substituted aromatic aldehydes with varied substitutions are described for the Biginelli reaction. An analysis was also performed to study the factors that affect the yield of the reaction.

RESULTS

When 1,3-dicarbonyl compound was ethyl acetoacetate, the CuCl/ conc.H2SO4 system gave the highest yield (90.5%). While when acetoacetamide was used, the yields of DHPMs in presence of PTSA/conc. HCl, conc. HCl or FeCl3•6H2O were all over 90%. Nine DHPMs with different substituents were obtained.

CONCLUSION

The Lewis acid or mixed catalyst had no significant advantage over a single protonic acid as catalyst. Conc. HCl as the catalyst was found to be the most effective condition for the preparation of DHPMs. The aromatic aldehyde with weak electron-withdrawing substituent such as Br resulted in the best yield.

An efficient synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one via a cesium carbonate-promoted direct condensation of 1-aryl-2-propanone with 1,1′-(arylmethylene)diurea

An efficient method for the synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one by using 1,1′-(arylmethylene)diurea and 1-aryl-2-propanone as substrates was developed. The reactions proceeded efficiently in the presence of Cs₂CO₃ to give the desired products in moderate to good yields with wide substrate scope and good functional group tolerance, serving as an attractive alternative or complement to the previously reported methods for the facile assembly of biologically and pharmaceutically active 3,4-dihydropyrimidin-2(1H)-ones.

A Cs₂CO₃-promoted efficient method for the synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one by using 1,1′-(arylmethylene)diurea and 1-aryl-2-propanone as substrates was developed.

Palygorskite-anchored Pd complexes catalyze the coupling reactions of pyrimidin-2-yl sulfonates

In this work, an anchored Pd complex (PGS–APTES–Pd(OAc)₂) was prepared via simple and green steps from the natural clay mineral palygorskite and was well characterized by XPS, XRD, IR, SEM, and EDX. This complex was further utilized as a fine catalyst for the C–C/C–N coupling reactions of pyrimidin-2-yl sulfonates. Subsequently, the cyclic utilization test indicated the high stability and sustainability of this PGS–APTES–Pd(OAc)₂ catalyst, and no activation was required in the recycling process, providing an applicable and reusable catalyst in organic synthesis.

PGS–APTES–Pd(OAc)₂ was prepared through simple and green steps from the natural clay mineral palygorskite. Obviously, the stability and reusability of PGS–APTES–Pd(OAc)₂ were superior to those of the PGS–Pd catalyst (prepared by the impregnation method) in recycling test.

Pre-emergence application of (thio)urea analogues compromises the development of the weed species Bidens pilosa, Urochloa brizantha, and Urochloa decumbens

Invasive species (weeds) contribute to great losses in crop productivity, and one of the strategies for controlling their distribution in the field involves the use of herbicides. However, the development of new formulations for the control of weeds is challenged by environmental issues, increases in the resistance of weeds to herbicides, and poor selectivity of herbicides towards invasive species. Here, by using pre-emergence experiments, we assessed the phytotoxicity of two (thio)urea analogues (2A10 and 2B2) against the weed species Bidens pilosa (a dicot), Urochloa brizantha and Urochloa decumbens (monocots). Similar to diuron (400 µM), which is a commercial urea analogue herbicide, the urea analogue 2A10 (>200 µM) was lethal to B. pilosa. Although 2A10 failed to disrupt the germination of U. brizantha seeds, this compound (≥600 µM) inhibited the accumulation of chlorophyll a and b and carotenoids and resulted in the development of seedlings that presented relatively short roots and small, chlorotic leaves. Moreover, the thiourea analogue 2B2 (≥600 µM) reduced the germination percentage of U. decumbens seeds and delayed their germination, and at a concentration of 800 µM, this analogue impaired root growth and blocked the formation of lateral roots. The presence of an oxygen atom in the urea moiety of the 2A10 structure is critical for its marked activity against B. pilosa seeds, as 2B2 bears a sulphur atom instead and marginally inhibits seed germination. Neither 2A10 nor 2B2 was toxic to the non-weed species Lactuca sativa (lettuce; a dicot), and the latter even exerted beneficial effects by stimulating leaf expansion. Therefore, the evaluated (thio)urea analogues are promising for the design and development of new phytotoxic compounds for the pre-emergent control of the spread of B. pilosa (2A10) or the post-emergence control of U. brizantha (2A10) and U. decumbens (2B2).

A Cu(ii) metal–organic framework with significant H2 and CO2 storage capacity and heterogeneous catalysis for the aerobic oxidative amination of C(sp3)–H bonds and Biginelli reactions

1 exhibits significant H₂, CO₂ storage capacity and heterogeneous catalytic activity for oxidative amination of C(sp³)–H bonds and Biginelli reactions.

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids.

Nucleophile-Mediated Ring Expansion of 5-Acyl-substituted 4-Mesyloxymethyl-1,2,3,4-tetrahydropyrimidin-2-ones in the Synthesis of 7-Membered Analogues of Biginelli Compounds and Related Heterocycles

A general six-step approach to alkyl 2-oxo-2,3,6,7-tetrahydro-1H-1,3-diazepine-5-carboxylates and 5-acyl-2,3,6,7-tetrahydro-1H-1,3-diazepin-2-ones based on the nucleophile-mediated ring expansion reaction of 5-functionalized 4-mesyloxymethyl-1,2,3,4-tetrahydropyrimidin-2-ones has been developed. Synthesis of the latter involved nucleophilic substitution of tosyl group in readily available N-[(2-benzoyloxy-1-tosyl)ethyl]urea with sodium enolates of β-oxoesters or 1,3-diketones, followed by dehydration or heterocyclization-dehydration of resulting products, removal of benzoyl protection, and conversion of hydroxymethyl group into mesyloxymethyl group. Conformations of the obtained tetrahydro-1H-1,3-diazepin-2-ones in solid state and solutions were established using X-ray diffraction and NMR spectroscopy. A plausible mechanism of tetrahydropyrimidine ring expansion based on DFT calculation at B3LYP/6-31+G(d,p) level and NMR monitoring experiments was discussed. The ring contraction reaction of methoxy- or phenylthio-diazepinones under acidic conditions resulted in the corresponding 3-functionalized 1-carbamoyl-1H-pyrroles.

New Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Catalyzed by Benzotriazolium-Based Ionic Liquids under Solvent-Free Conditions

An efficient synthesis of novel 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) and their derivatives, using Brønsted acidic ionic liquid [C₂O₂BBTA][TFA] as a catalyst, from the condensation of aryl aldehyde, β-ketoester and urea was described. Reactions proceeded smoothly for 40 min under solvent-free conditions and gave the desirable products with good to excellent yields (up to 99%). The catalyst could be easily recycled and reused with similar efficacies for at least six cycles.

Synthesis and fluorescence of pyrazolines substituted with pyrimidine and ferrocene subunits

1,3,5-Trisubstituted 2-pyrazolines were synthesized by the reaction of chalcones with hydrazine in hot ethanol. Their structures were elucidated by 1H NMR, 13C NMR, IR, MS and elemental analysis. The fluorescence spectra were measured in different organic solvents. The emission wavelength is blue shifted with the increase in solvent polarity.

An Efficient Amide-Aldehyde-Alkene Condensation: Synthesis for the N-Allyl Amides

The allylamine skeleton represents a significant class of biologically active nitrogen compounds that are found in various natural products and drugs with well-recognized pharmacological properties. In this personal account, we will briefly discuss the synthesis of allylamine skeletons. We will focus on showing a general protocol for Lewis acid-catalyzed N-allylation of electron-poor N-heterocyclic amides and sulfonamide via an amide-aldehyde-alkene condensation reaction. The substrate scope with respect to N-heterocyclic amides, aldehydes, and alkenes will be discussed. This method is also capable of preparing the Naftifine motif from N-methyl-1-naphthamide or methyl (naphthalene-1-ylmethyl)carbamate, with paraformaldehyde and styrene in a one-pot manner.

Potential antitumoral 3,4-dihydropyrimidin-2-(1H)-ones: synthesis, in vitro biological evaluation and QSAR studies

The search for novel anticancer agents with higher selectivity and lower toxicity remains a medical need.

Catalyst-free Biginelli-type synthesis of new functionalized 4,7-dihydropyrazolo[1,5-a]pyrimidines

New pyrazolopyrimidines and pyrazoloquinazolines were synthesized through the uncatalyzed reaction of 5-amino-3-arylpyrazole-4-carbonitriles with aldehydes and 1,3-dicarbonyl compounds.

Convenient NaCl-Catalysed Multicomponent Synthesis of Spiro[indoline-3,4′-Pyrano[2,3-c]Pyrazole]-3′-Carboxylate Derivatives in Aqueous Medium

A series of alkyl 6′-amino-5′-cyano-2-oxo-1′H-spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-3′-carboxylates has been synthesised in the presence of sodium chloride as catalyst in water. The green synthesis shows attractive green characteristics such as, using water as the reaction medium, very short reaction time, easy work up, and reduced waste.

4-Aryl-Pyrimidin-2-Yl Tosylates as Efficient Reaction Partners: Application to the Synthesis of Pyrimidines Functionalised with Propargyloxy and 1,2,3-Triazolo Groups

The 4-arylated pyrimidin-2-yl tosylate derivatives, easily prepared from cheap commercial materials, reacted efficiently with propargyl alcohol/NaOBut to give the corresponding 4-arylated 2-propargyloxy-pyrimidine derivatives which, in a one-pot reaction catalysed by CuSO4·5H2O/sodium ascorbate, reacted with NaN3 and hexyl or benzyl bromide to give a series of 2-(1-hexyl- or 1-benzyl-1,2,3-triazol-4-yl)methoxy-pyrimidine derivatives in good yields.