Search Results (17)

1-[(4S)-4-benzyl-1,3-oxazolidin-2-one-3-yl]propyltriphenylphosphonium tetrafluoroborate was synthesized in a two-step procedure starting from (4S)-4-benzyl-3-propionyl-1,3-oxazolidin-2-one. In the first step, (4S)-4-benzyl-3-propionyl-1,3-oxazolidin-2-one was treated with DIBAL-H at −78 °C in DCM and then converted to (4S)-4-benzyl-3-(1-trimethylsilyloxy)propyl-1,3-oxazolidin-2-one with TMSOTf at −78 °C in DCM in the presence of pyridine. Next, the silylated intermediate was transformed to the expected 1-[(4S)-4-benzyl-1,3-oxazolidin-2-one-3-yl]propyltriphenylphosphonium tetrafluoroborate by reaction with Ph₃P·HBF₄ at −40 °C in DCM. The structures of the compounds obtained were confirmed by spectroscopic methods (¹H-, ¹³C{¹H}-, ³¹P{¹H}-NMR, IR) and HRMS analysis. Full article

2-methylcamalexin, a novel derivative of the phytoalexin Camalexin, was synthesized for the first time, using a convenient two-step approach. The approach realizes coupling of two aromatic heterocyclic moieties (2-methylindole and thiazole) by sequential α-amidoalkylation/oxidative re-aromatization. The target product was obtained in a cost-effective manner, with 88% yield over two steps. The structure of the synthesized product was unequivocally determined on the basis of NMR, HRMS and FTIR spectral measurments. Full article

1,3-Thiazole derivatives are of interest in pharmacy, medicine, and agriculture as potential biologically active substances. We have proposed for the first time a convenient and effective method for the synthesis of amidoalkylated derivatives of 2-amino-1,3-thiazole. This approach is based on the reaction of amidoalkylated thioureas with α-halocarbonyl compounds. The reaction was carried out under stirring at 20 °C in ethanol with the addition of an equimolar amount of triethylamine to bind the released hydrogen halide. The yield of the obtained 1,3-thiazole derivatives was 68–75%. An attempt to carry out a counter-synthesis by amidoalkylation of the corresponding 2-amino-1,3-thiazole derivative was unsuccessful due to strong resinification of the reaction mass. The structure of the compounds obtained was confirmed by ¹H and ¹³C NMR spectroscopy. The structure was finally confirmed by X-ray structural analysis performed for N-(2,2,2-trichloro-1-((4-phenylthiazol-2-yl)amino)ethyl)acetamide. Full article

Methoxycamalexins are close structural derivatives of the indolic phytoalexin Camalexin, which is a well-known drug lead with an antiproliferative and antioxidant profile. 6-methoxycamalexin, 7-methoxycamalexin, and 6,7-dimethoxycamalexin are natural bioactive products, and there is significant interest in the development of efficient methods for the synthesis of structurally related analogues. Herein, we describe an efficient and high-yielding method for the synthesis of variously substituted hydroxy-, bezyloxy, and methoxycamalexins. A set of methoxy-, hydroxy-, and benzyloxy-indoles were successfully amidoalkylated with N-acyliminium reagents derived in situ from the reaction of thiazole or methylthiazoles with Troc chloride. Eleven novel N-acylated analogues were synthesized, with yields ranging from 77% to 98%. Subsequent oxidative reactions with o-chloranil or DDQ led to 10 novel oxy-camalexins in 62–98% yield. This two-step approach allowed the synthesis of two 4,6-dimethoxy camalexins, which are difficult to obtain using published methods. The structure of the obtained products was unequivocally determined by ¹H-, ¹³C{¹H}-, HSQC-NMR, FTIR, and HRMS spectral analyses. An in silico assay was carried out on the obtained products to assess their general toxicity and physicochemical properties, including their compliance with Lipinski’s rule of five. The results indicate that all compounds have good potential to be developed as drugs or agrochemicals. Full article

The Thymus vulgaris and Origanum vulgare essential oils (contained thymol and carvacrol in a range of 35–80%) are used in various products in the fields of medicine, cosmetics, and foods. Molecular hybridization between benzothiazole (BT) and phenolic monoterpenoids is a promising method for the development of biologically active compounds. New benzothiazole–monoterpenoid hybrids were synthesized through a regioselective α-amidoalkylation reaction of thymol and carvacrol with high yields (70–96%). This approach is both simple and cost-effective, employing easily accessible and inexpensive reagents to produce target molecules. The structure of the synthesized compounds was characterized spectrally using ¹H-, ¹³C-NMR, FT-IR, and HRMS data. The newly obtained compounds are structural analogues of the UVB filter PBSA, which is used in cosmetics. The spectral properties of the aromatic products thymol hybrid (2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole) and carvacrol hybrid (2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole) were successfully examined, using a validated spectrophotometric method. SPF values varied from 31 to 36, compared to the PBSA (30), and were observed at concentrations of 1–0.25 mM. 2-Hydroxyphenylbenzothiazoles are known antimicrobial and antioxidant agents that have potential applications in the food industry and cosmetics as preservatives and antioxidants. In this context, antimicrobial activity of the hybrid compounds was evaluated using the agar diffusion method against E. coli, S. aureus, P. aeruginosa, and C. albicans. Compounds of methyl-2-(4-hydroxy-2-isopropyl-5-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate containing carvacrol fragments showed high activity against Staphylococcus aureus ATCC 25923 (with 0.044 μmol content). The radical scavenging activity was determined using ABTS and DPPH assays, the highest activity was exhibited by the thymol hybrids ethyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—133.70 ± 10 µM) and methyl-2-(4-hydroxy-5-isopropyl-2-methylphenyl)benzo[d]thiazole-3(2H)-carboxylate (IC₅₀—157.50 ± 10 µM), defined by ABTS. The aromatic benzothiazole–monoterpenoid hybrids are classified using in silico analyses as non-mutagenic, with low toxicity, and they are non-irritating to the skin. These compounds were identified as new hit scaffolds for multifunctional molecules in cosmetics. Full article

In this study, [(N-benzamidomethyl)(N-benzoyl)amino]methyltriphenylphosphonium tetrafluoroborate was synthesized at 80 °C, starting from N-benzoylaminomethyltriphenylphosphonium tetrafluoroborate, by a specific α-amidoalkylation reaction using Hünig’s base as a catalyst. N-benzoylaminomethyltriphenylphosphonium tetrafluoroborate acts as both an amidoalkylating agent and a nucleophile precursor. The structure of the compound obtained was confirmed by spectroscopic methods (¹H-, ¹³C-, ³¹P-NMR, IR) and HR-MS analysis. Full article

Mechanochemistry has emerged as a potential alternative for organic transformations, leveraging substrate availability, stability, and reduced solvent use. Its high efficiency and eco-friendly profile have garnered significant attention, particularly in the pharmaceutical industry, where it is hailed as the most promising environmentally friendly method for organic synthesis. This approach harnesses mechanical energy to stimulate or accelerate chemical changes, offering a green and effective means to obtain organic molecules. We employed an innovative green and eco-friendly approach—mechanochemical, solvent-free, and heterogeneously catalyzed—to synthesize a series of new biofunctional hybrid molecules, specifically derivatives of biologically active 1,2,3,4-tetrahydroisoquinoline alkaloids. Our method involves a mechanochemically driven intramolecular α-amidoalkylation reaction. To facilitate this reaction under acidic conditions, we successfully utilized polyphosphoric acid on silica as a heterogeneous catalyst. This approach enables the rapid and straightforward synthesis of novel compounds without the generation of byproducts or waste. All newly obtained bio-functional hybrid compounds were fully characterized via ¹H, ¹³C NMR, UV, and mass spectral data. In our quest for environmentally sustainable synthesis methods, we made a significant breakthrough by synthesizing a series of innovative N-ibuprofen-substituted 1,2,3,4-tetrahydroisoquinolines through solvent-free mechanosynthesis. These novel derivatives offer exciting prospects for studying their biological properties and investigating correlations between structure and activity. Full article

Isoquinoline alkaloids constitute a substantial category of natural products, among which 1,2,3,4-tetrahydroisoquinoline (THIQ) holds significance. THIQ-based compounds, whether natural or synthetic, showcase a wide array of biological activities, demonstrating efficacy against diverse infectious pathogens and neurodegenerative disorders. Consequently, THIQ heterocyclic structures have garnered considerable interest within the scientific realm, driving the exploration and synthesis of novel THIQ derivatives with notable biological potential. In contrast, flurbiprofen falls under the category of nonsteroidal anti-inflammatory drugs (NSAIDs) and demonstrates both antipyretic and analgesic effects. Its potential extends beyond mere pain relief; it has been suggested for both local and systemic applications, such as inhibiting colon tumor growth and platelet aggregation. In our research, we focus on synthesizing novel N-flurbiprofen-substituted 1,2,3,4-tetrahydroisoquinolines. We explore novel methods for the amide cyclization, investigating the feasibility of utilizing new environmentally friendly reagents. Specifically, we examine the efficacy of strong protic acids that are immobilized on a silica gel as heterogeneous acid catalysts in intramolecular α-amidoalkylation reactions. These acid-supported silica gel systems are pivotal in acid-catalyzed synthetic processes, emerging as preferred options for producing novel organic compounds, aligning with eco-friendly practices. Our interest lies in applying this heterogeneous acid system on a silica gel as a “heterogeneous catalyst” to synthesize isoquinoline derivatives of flurbiprofen and elucidate the relationship between their structure and activity. When investigating the intramolecular α-amidoalkylation reaction, we conduct multiple experiments to determine the ideal reaction conditions. This involves altering solvents and acid reagents while considering the acid-catalyzed nature of the reaction. The novel compounds were successfully synthesized through an intramolecular α-amidoalkylation reaction. This synthesis method involved heating the reactants at 80 °C in dichloroethane, supplemented with a heterogeneous acid catalyst, PPA/SiO₂. The obtained compounds underwent full spectral characterization using ¹H and ¹³C NMR, IR spectroscopy, and mass analysis. Full article

N-acyliminium-type cations are examples of highly reactive intermediates that are willingly used in organic synthesis in intra- or intermolecular α-amidoalkylation reactions. They are usually generated in situ from their corresponding precursors in the presence of acidic catalysts (Brønsted or Lewis acids). In this context, 1-aminoalkyltriarylphosphonium derivatives deserve particular attention. The positively charged phosphonium moiety located in the immediate vicinity of the N-acyl group significantly facilitates C_α-P⁺ bond breaking, even without the use of catalyst. Moreover, minor structural modifications of 1-aminoalkyltriarylphosphonium derivatives make it possible to modulate their reactivity in a simple way. Therefore, these types of compounds can be considered as smart synthetic equivalents of N-acyliminium-type cations. This review intends to familiarize a wide audience with the unique properties of 1-aminoalkyltriarylphosphonium derivatives and encourage their wider use in organic synthesis. Hence, the most important methods for the preparation of 1-aminoalkyltriarylphosphonium salts, as well as the area of their potential synthetic utilization, are demonstrated. In particular, the structure–reactivity correlations for the phosphonium salts are discussed. It was shown that 1-aminoalkyltriarylphosphonium salts are not only an interesting alternative to other α-amidoalkylating agents but also can be used in such important transformations as the Wittig reaction or heterocyclizations. Finally, the prospects and limitations of their further applications in synthesis and medicinal chemistry were considered. Full article

An convenient one-pot approach for the synthesis of new (E)-2-(2-oxo-4-phenylbut-3-en-1-yl)benzo[d]thiazole-3(2H)-carboxylates is demonstrated. The method is based on a three-component reaction of benzylideneacetone with electrophilic N-alkoxycarbonylbenzothiazolium species formed in situ. The newly synthesized compounds were fully characterized by 1D ¹H, ¹³C- NMR, IR and MS. Full article

Herein we describe the development and optimization of a two-step procedure for the synthesis of N-protected 1-aminomethylphosphonium salts from imides, amides, carbamates, or lactams. Our “step-by-step” methodology involves the transformation of amide-type substrates to the corresponding hydroxymethyl derivatives, followed by the substitution of the hydroxyl group with a phosphonium moiety. The first step of the described synthesis was conducted based on well-known protocols for hydroxymethylation with formaldehyde or paraformaldehyde. In turn, the second (substitution) stage required optimization studies. In general, reactions of amide, carbamate, and lactam derivatives occurred at a temperature of 70 °C in a relatively short time (1 h). On the other hand, N-hydroxymethylimides reacted with triarylphosphonium salts at a much higher temperature (135 °C) and over longer reaction times (as much as 30 h). However, the proposed strategy is very efficient, especially when NaBr is used as a catalyst. Moreover, a simple work-up procedure involving only crystallization afforded good to excellent yields (up to 99%). Full article

α-Aminophosphonic acids are phosphorus analogues of α-amino acids. Compounds of this type find numerous applications in medicine and crop protection due to their unique biological activities. A crucial factor in these activities is the configuration of the stereoisomers. Only a few methods of stereoselective transformation of α-amino acids into their phosphorus analogues are known so far and all of them are based on asymmetric induction, thus involving the use of a chiral substrate. In contrast, we have focused our efforts on the development of an effective method for this type of transformation using a racemic mixture of starting N-protected α-amino acids and a chiral catalyst. Herein, a simple and efficient stereoselective organocatalytic α-amidoalkylation of dimethyl phosphite by 1-(N-acylamino)alkyltriphenylphosphonium salts to enantiomerically enriched α-aminophosphonates is reported. Using 5 mol% of chiral quinine- or hydroquinine-derived quaternary ammonium salts provides final products in very good yields up to 98% and with up to 92% ee. The starting phosphonium salts were easily obtained from α-amino acid derivatives by decarboxylative methoxylation and subsequent substitution with triphenylphosphonium tetrafluoroborate. The appropriate self-disproportionation of enantiomers (SDE) test for selected α-aminophosphonate derivatives via achiral flash chromatography was performed to confirm the reliability of the enantioselectivity results that were obtained. Full article

α-Vinyl or α-acetylenyl azacycles were easily synthesized from 7- to 9-membered lactams and 6- to 9-membered lactams via N,O-acetal trimethylsilyl (TMS) ethers. Organocopper and organostannane reagents afforded reasonable yields for the respective N-acyliminium ion vinylation and acetylenylation intermediates generated from N,O-acetal TMS ethers in the presence of a Lewis acid. Full article

The α-amidoalkylating properties of 1-(N-acylamino)alkyltriarylphosphonium salts with weakened C_α-P⁺ bond strength are discussed and examined. It is demonstrated that such type of phosphonium salts reacts smoothly with a diverse array of carbon- and heteroatom-based nucleophiles, including 1-morpholinocyclohexene, 1,3-dicarbonyl compounds, benzotriazole sodium salt, p-toluenesulfinate sodium salt, benzylamine, triarylphosphines, and other P-nucleophiles. Reactions are conducted at room temperature, in a short time (5–15 min) and mostly without catalysts. Simple work-up procedures result in good or very good yields of products. The structures of known compounds were established by spectroscopic methods and all new compounds have been fully characterized using ¹H-, ¹³C-, ³¹P-NMR, IR spectroscopy, and high-resolution mass spectrometry. Mechanistic aspects of described transformations are also performed and discussed. It was demonstrated that unique properties make 1-(N-acylamino)alkyl-triarylphosphonium salts with weakened C_α-P⁺ bond strength interesting building blocks with great potential, especially in α-amidoalkylation reactions. Full article