Synthesis and antiproliferative activity evaluation of steroidal imidazo[1,2-a]pyridines

Insights into medicinal attributes of imidazo[1,2-a]pyridine derivatives as anticancer agents

Cancer ranks among the most life-threatening diseases worldwide and is continuously affecting all age groups. Consequently, many research studies are being carried out to develop new cancer treatments, but many of them experience resistance and cause severe toxicity to the patients. Therefore, there is a continuous need to design novel anticancer agents that are target-based, have a higher potency, and have minimal toxicity. The imidazo[1,2-a]pyridine (IP) pharmacophore has been found to be a prominent moiety in the field of medicinal chemistry due to its vast biological properties. Also, it holds immense potential for combating cancer with minimal side effects, depending on the substitution patterns of the core structure. IPs exhibit significant capability in regulating various cellular pathways, offering possibilities for targeted anticancer effects. The present review summarizes the anticancer profile of numerous IP derivatives synthesized and developed by various researchers from 2016 till now, as inhibitors of phosphoinositide-3-kinase/mammalian target of rapamycin (PI3K/mTOR), protein kinase B/mammalian target of rapamycin (Akt/mTOR), aldehyde dehydrogenase (ALDH), and tubulin polymerization. This review provides a comprehensive analysis of the anticancer activity afforded by the discussed IP compounds, emphasizing the structure-activity-relationships (SARs). The aim is also to underscore the potential therapeutic future of the IP moiety as a potent partial structure for upcoming cancer drug development and to aid researchers in the field of rational drug design.

Design and synthesis of phosphoryl-substituted steroidal pyridazines (Pho-STPYRs) as potent estrogen receptor alpha inhibitors: targeted treatment of hormone-dependent breast cancer cells

Estrogen receptor alpha (ERα) is an important target for the discovery of new therapeutic drugs against hormone-dependent breast cancer. A series of phosphoryl-substituted steroidal pyridazines (Pho-STPYRs) were synthesized and biologically evaluated as potent ERα inhibitors. Pho-STPYRs showed cytotoxicity against breast cancer cells with IC50 values of 5.9 μM and higher. Pho-STPYRs 33 and 34 [IC50 (MCF7) = 6.5 and 5.9 μM, respectively] were found to block the expression of ERα, the main driver of breast cancer growth, and modulate the ERK, cyclin D1, and CDK4 pathways. Compound 34 showed selectivity, anti-estrogenic potency and high antiproliferative efficacy in combination with the AKT inhibitor. Molecular docking was used to more accurately define the binding mode of lead compounds 33 and 34 to ERα. The selectivity analysis showed that lead compounds 33 and 34 produce no effects on cytochromes P450, including CYP7A1, CYP7B1, CYP17A1, CYP19A1, and CYP21A2. In a word, Pho-STPYRs 33 and 34 are promising ERα inhibitors for the treatment of hormone-dependent breast cancer.

Exploration and biological evaluation of 20-vinyl pregnenes: A step forward toward selective modulators of the estrogen receptor α signaling for breast cancer treatment

A series of D-ring modified steroids bearing a vinyl ketone pendant were synthesized and evaluated for antiproliferative activity against breast cancer cell line and cytochromes P450. The lead compound, 21-vinyl 20-keto-pregnene (2f) (IC50 = 2.4 µM), was shown to be a promising candidate for future anticancer drug design, particularly against estrogen receptor α (ERα)-positive breast cancer. The lead compound was found to have a significant effect on the signaling pathways in parental and 4-hydroxytamoxifen-resistant cells. Compound 2f modulated the ERK, cyclin D1, and CDK4 pathways and blocked the expression of ERα, the main driver of breast cancer growth. Compound 2f significantly reduced 17β-estradiol-induced progesterone receptor expression. Accumulation of cleaved poly(ADP-ribose) polymerase in cells treated with compound 2f indicated induction of apoptosis. The selectivity analysis showed that lead compound 2f produces no significant effects on cytochromes P450, CYP19A1, CYP21A2, and CYP7B1.

Synthesis and biological activities of bicyclic pyridines integrated steroid hybrid

Reports on structural modification of heterosteroids through various reactions, and developed synthetic routes have considerably increased over the last decade. The present review encompasses the applicable approaches dealing with the utility of reactive moieties in various steroids for the synthesis of fused bicyclic pyridines, and binary bicyclic pyridines all over the years. The different sections include the synthesis of steroids-fused, and binary quinolines, pyridopyrimidines, imidazopyridines, spirocyclic imidazopyridines, pyrazolopyridines, thienopyridines, pyridinyl-thiazoles, and tetrazolopyridine hybrids, as well as, the diverse biological applications of these heterocyclic steroids. The researchers' interest was principally focused on investigating the flexibility of synthetic strategies for various derivatives of natural steroids and building proposals based on heterocyclic steroids for drug discovery, biological assessments, and synthetic applications.

Synthesis, biological activities, and future perspectives of steroidal monocyclic pyridines

Steroidal pyridines are a class of compounds that have been the subject of extensive research in recent years due to their potential biological activities. The introduction of a pyridine ring into the steroid skeleton can significantly alter the chemical and biological properties of the compound, making it more potent and/or selective for a particular target. Different synthetic methods have been developed for the preparation of steroidal pyridines. This review provides an overview of the synthesis, biological activities, and future perspectives of steroidal monocyclic dihydropyridines, tetrahydropyridines, and pyridines from 2005 to the present. The different synthetic methods that have been developed for the preparation of these steroids are discussed, as well as the proposed mechanisms and the biological activities that have been reported. Finally, the potential of steroidal monocyclic pyridines for the development of new drugs is discussed. This review is intended to provide a comprehensive overview of the field of steroidal monocyclic pyridines for researchers and scientists who are interested in this area of research. It is also hoped that this review will stimulate further research into the synthesis and biological activities of steroidal pyridines to develop new and improved drugs for the treatment of diseases.

Discovery of highly potent proapoptotic antiestrogens in a series of androst-5,16-dienes D-modified with imidazole-annulated pendants

Heterocyclic derivatives of steroid hormones are potent anticancer agents, which are used in the chemotherapy of breast and prostate cancers. Here, we describe a novel series of androstenes, D-modified with imidazole-annulated pendants, with significant anticancer activity. Novel C17-linked imidazole-annulated heterocyclic derivatives of dehydropregnenolone acetate were synthesized by the cyclocondensation with amidines using 3β-acetoxy-21-bromopregna-5,16-dien-20-one as the substrate. The antiproliferative potency of all the synthesized compounds was evaluated against human prostate (22Rv1) and human breast (MCF7) cancer cell lines and cytochromes P450. The lead compound, imidazo[1,2-a]pyridine derivative 3h, was revealed to be a promising candidate for future anticancer drug design, particularly against ERα-positive breast cancer. Lead compound 3h was found to be selective against MCF7 cells with IC₅₀ of 0.1μM and to act as both a potent selective agent blocking estrogen receptor α, which is involved in the stimulation of breast cancer growth, and an effective apoptosis inducer. The potential ability of compound 3h to bind to ERα was studded using molecular docking and molecular dynamics simulation. The selectivity analysis showed that lead steroid 3h produces no effects on cytochromes P450 CYP17A1, CYP7A1, and CYP21A2.

Oxazolinyl derivatives of androst-16-ene as inhibitors of CYP17A1 activity and prostate carcinoma cells proliferation: Effects of substituents in oxazolinyl moiety

Steroid derivatives modified with nitrogen containing heterocycles are known to inhibit activity of steroidogenic enzymes, decrease proliferation of cancer cells and attract attention as promising anticancer agents. Specifically, 2'-(3β-hydroxyandrosta-5,16-dien-17-yl)-4',5'-dihydro-1',3'-oxazole 1a potently inhibited proliferation of prostate carcinoma cells. In this study we synthesized and investigated five new derivatives of 3β-hydroxyandrosta-5,16-diene comprising 4'-methyl or 4'-phenyl substituted oxazolinyl cycle 1 (b-f). Docking of compounds 1 (a-f) to CYP17A1 active site revealed that the presence of substitutents at C4' atom in oxazoline cycle, as well as C4' atom configuration, significantly affect docking poses of compounds in the complexes with enzyme. Testing of compounds 1 (a-f) as CYP17A1 inhibitors revealed that the only compound 1a, comprising unsubstituted oxazolinyl moiety, demonstrated strong inhibitory activity, while other compounds 1 (b-f) were slightly active or non active. Compounds 1 (a-f) efficiently decreased growth and proliferation of prostate carcinoma LNCaP and PC-3 cells at 96 h incubation; the effect of compound 1a was the most powerful. Compound 1a efficiently stimulated apoptosis and caused PC-3 cells death, that was demonstrated by a direct comparison of pro-apoptotic effects of compound 1a and abiraterone.

Photostability and Antiproliferative Activity of Furan Analogues of Combretastatin A-4

Cancer is one of the most serious health problems that usually require heavy medical treatment. It is important to ensure that no additional burden is placed on patients due to the modes of administration and/or poor quality of pharmaceuticals. In this regard, understanding, quantifying, and improving the photostability (resistance to UV light or sunlight) of drugs is among the important elements that can improve the patient's quality of life. In this work, the photochemical properties of a wide range of furanone analogues of combretastatin A-4 and their antiproliferative activity against A-431 epidermoid carcinoma cells were studied in a search for compounds with improved photostability and antiproliferative activity. It was found that the incorporation of an arylidene moiety led to a significant improvement in photostability, while the antiproliferative activity strongly depends on the nature of the aryl residue in the arylidene moiety. The high photostability of arylidenes was achieved due to the delocalization of the central double bond of the 1,3,5-hexatriene system, which limited the 6π-electrocyclization. The best results in terms of antiproliferative activity were obtained for thiophene arylidene (IC₅₀ = 0.6 μM) and 3,4-diarylfuran (IC₅₀ = 0.047 μM). The obtained results address the lack of data available now in scientific literature on the photodegradation of combretastatin A-4 analogues and should be taken into account in studies of the side effects of pharmaceuticals based on them.

Synthesis and crystal structures of D-annulated pentacyclic steroids: looking within and beyond AR signalling in prostate cancer

Carbocyclic steroids D-annulated at 16α and 17α positions with a 5-membered ring E are easily accessible via the interrupted Nazarov cyclization. Three steroid series have been structurally studied: chlorine-containing D-annulated...

Gas-phase fragmentation of protonated 3-phenoxy imidazo[1,2-a] pyridines using tandem mass spectrometry and computational chemistry

Imidazo[1,2-a] pyridine is one of the pharmaceutically important scaffolds and has been widely studied due to its extensive biological activities. In this work, electrospray ionization tandem mass spectrometry (ESI-MS/MS) in positive mode was used to study the gas-phase fragmentation behavior of a series of 3-phenoxy imidazo[1,2-a] pyridines. Proposed fragmentation pathways were supported by ESI-MS/MS data and computational thermochemistry. Homolytic cleavage of the 3-phenoxy C-O bond was the characteristic fragmentation of 3-phenoxy imidazo [1,2-a] pyridines. The eliminations of the one substituted phenoxy radical and CO produced other diagnostic ions for 3-phenoxy imidazo [1,2-a] pyridines, which were useful to identify the 3-phenoxy group and imidazo [1,2-a] pyridine scaffold. The results contribute to the further understanding of the gas-phase fragmentation of 3-phenoxy imidazo [1,2-a] pyridines and the identification of other analogs using tandem mass spectrometry techniques.

Secosteroidal hydrazides: Promising scaffolds for anti-breast cancer agents

A convenient and selective approach to 13,17-secoestra-1,3,5(10)-trien-17-oic acid hydrazides and their N'-(het)arylmethylene derivatives was disclosed and these novel types of secosteroids were screened for cytotoxicity against hormone-dependent human breast cancer cell line MCF-7. A number of 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N'-(het)arylmethylene]hydrazides show significant cytotoxic effect comparable or superior to that for reference drug cisplatin. Compound 3l exhibits the highest activity with the IC₅₀ value of about 2 μM and is 2.8 times more active than cisplatin. Hit 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N'-(het)arylmethylene]hydrazides 3d, 3l and 3q are characterized by high cytotoxicity and good selectivity towards MCF-7 breast cancer cells. The synthesized secosteroids may be considered as new promising antitumor agents.

Investigation of the effect of steroidal imidazoheterocycles hormone derivatives on JEG-3 trophoblast cells of choriocarcinoma

This study aimed to examine the biological activities of unique steroid hormone derivatives-steroidal imidazoheterocycles. The activity synthesized steroidal compounds were tested for the viability of JEG-3 trophoblast cells of choriocarcinoma. The results of the MTT cytotoxicity test showed that most of the examined steroidal imidazoheterocycles act proliferatively on the JEG-3 cell line, except (E, F, and J). Antiproliferative activity of these derivates is probably influenced by different substituents at position 17-C atom in the chemical structure of the hormone and by different substituents on the oxygen atom of acetamide group in the hormone molecule. In order to better confirm the antiproliferative activity of these derivatives, it is necessary to performed complex research on a large panel of cancer cell lines and by different assay.

Fe(iii)-Catalyzed synthesis of steroidal imidazoheterocycles as potent antiproliferative agents

An efficient and practical method has been developed for the synthesis of steroidal imidazoheterocycles via cost-effective and environmentally benign FeCl₃-catalyzed oxidative amination. A library of steroidal imidazo[1,2-a]pyridines was directly synthesized from readily available 2-aminopyridines and steroidal ketones in aerobic conditions. The synthesized compounds were screened for activity on human microsomal cytochrome P450s CYP7, CYP17 and CYP21. Antiproliferative activity of two lead compounds 3ia and 3la was additionally evaluated against the human MCF-7 (breast cancer), SKOV3 (ovarian cancer), and 22Rv1 (prostate cancer) cell lines. Steroidal imidazo[1,2-a]pyridine 3la which is a substrate molecule for CYP17A1 with IC₅₀ = 1.7 μM (MCF-7), 3.0 (SKOV3), and 6.0 μM (22Rv1) has proved to be more active than reference drug cisplatin.

Design, synthesis, and biological evaluation of imidazopyridine-linked thiazolidinone as potential anticancer agents

In this study, two series of imidazopyridine-linked thiazolidinone rings (5a-h and 6a-h) constituting 16 new compounds were synthesized and tested for their antiproliferative activity against a panel of three human cancer cell lines, that is, MCF-7 (human breast cancer), A549 (human lung cancer), and DU145 (human prostate cancer). Three compounds, 5h, 6f, and 6h, exhibited remarkable results against all three cell lines, but compound 6h was found to be the most active one against the breast cancer cell line. Among all the synthesized compounds, 6h displayed the highest antioxidant results. Furthermore, the potent compounds 5h, 6f, and 6h showed no signs of toxicity at doses ranging from 50 to 500 mg/kg of animal body weight. The biochemical parameters (SGOT and SGPT) of compound 6h nearly matched the control in hepatotoxicity studies. The molecular docking and MM-GBSADG binding studies are in agreement with the in vitro anticancer and antioxidant activity results. The most promising compound 6h was found to have the highest docking score and binding energy, and its absorption, distribution, metabolism, and excretion (ADME) parameters are in the acceptable range. Thus, it can be concluded that 6h, an imidazopyridine derivative endowed with a thiazolidinone ring system, has the potential to be developed as an anticancer agent.

Copper-imidazo[1,2-a]pyridines induce intrinsic apoptosis and modulate the expression of mutated p53, haem-oxygenase-1 and apoptotic inhibitory proteins in HT-29 colorectal cancer cells

Metastatic colorectal cancer responds poorly to treatment and is a leading cause of cancer related deaths. Worldwide, chemotherapy of metastatic colorectal cancer remains plagued by poor efficacy, development of resistance and serious adverse effects. Copper-imidazo[1,2-a]pyridines were previously shown by our group to be selectively active against several cancer cell lines, with three complexes, JD46(27), JD47(29), and JD88(21), showing IC₅₀ values between 0.8 and 1.8 μM against HT-29 cells. Here, we report that treatment with the copper complexes resulted in fragmented nuclei suggestive of apoptotic cell death, which was confirmed by increased annexin V binding and caspase-3/7 activity. The copper complexes caused a loss of mitochondrial membrane potential and increased caspase-9 activity. The absence of caspase-8 activity indicated activation of the intrinsic pathway. Proteomic analysis revealed that copper-imidazo[1,2-a]pyridines decreased the expression of phosphorylated forms of p53 [phospho-p53(S15), phospho-p53(S46) and phospho-p53(S392)]. The expression of inhibitor of apoptosis proteins, XIAP, cIAP1, livin, and the antiapoptotic proteins, Bcl-2 and Bcl-x, was decreased. HO/HMOX/HSP32, expression was notably increased, which suggested the accumulation of reactive oxygen species. Increased expression of TRAIL-R2/DR5 death receptor indicated the possible dual activation of both the extrinsic and intrinsic apoptotic pathways; however, caspase-8 activation could not be demonstrated. In conclusion, the copper-imidazo[1,2-a]pyridines were effective inducers of apoptotic cell death at low micromolar concentrations and changed the expression levels of proteins important for cell survival and cell death. These copper complexes may be useful tools to better understand the complexity of signalling networks in cancer cell death in response to cell stress.

Novel steroidal 1,3,4-thiadiazines: Synthesis and biological evaluation in androgen receptor-positive prostate cancer 22Rv1 cells

A flexible approach to previously unknown spirofused and linked 1,3,4-thiadiazine derivatives of steroids with selective control of heterocyclization patterns is disclosed. (N-Arylcarbamoyl)spiroandrostene-17,6' [1,3,4]thiadiazines and (N-arylcarbamoyl)17-[1',3',4']thiadiazine-substituted androstenes, novel types of heterosteroids, were prepared from 16β,17β-epoxypregnenolone and 21-bromopregna-5,16-dien-20-one in good to high yields by the treatment with oxamic acid thiohydrazides. The synthesized compounds were screened for antiproliferative activity against the human androgen receptor-positive prostate cancer cell line 22Rv1. Most of (N-arylcarbamoyl)17-[1',3',4']thiadiazine-substituted androstenes exhibit better antiproliferative potency (IC₅₀ = 2.1-6.6 µM) than the antiandrogen bicalutamide. Compounds 7d with IC₅₀ = 3.0 μM and 7j with IC₅₀ = 2.1 μM proved to be the most active in the series under study. Lead synthesized compound 7j downregulates AR expression and activity in 22Rv1 cells. NF-κB activity is also blocked in 7j-treated 22Rv1 cells. Apoptosis is considered as a possible mechanism of 7j-induced cell death.

[Design and synthesis of imidazo-fused heterocycles derivatives and their anti-tumor activity against breast cancer in mice]

OBJECTIVE

To synthesize compounds based on imidazo-fused heterocycles and evaluate their anti-tumor activity against breast cancer.

METHODS

The compounds 1a-1e, 2a and 2b were synthesized by aerobic copper-catalyzed halocyclization of methyl N-heteroaromatics with aliphatic amines; 3a and 3b were generated by sonogashira reaction and Suzuki reaction, respectively; the compounds 4a-4c were obtained by Buchwald-Hartwig reaction of the corresponding amines and 1e. The effects of these compounds against breast cancer cells and their nephrotoxicity were determined using MTT assay. Annexin VFITC/PI apoptosis detection kit was used to assess the apoptosis-inducing effects of these compounds in breast cancer cells. With normal saline as the control, the safety and anti-tumor activity of the compound 2a (daily dose of 10 mg/kg for 14 days) was tested in a mouse model bearing human breast cancer xenografts.

RESULTS

The compounds 2a, 4a, 4b and 4c all showed obvious anti-tumor activities. Among these compounds, 2a showed the most potent anti-tumor effect against breast cancer cells with an IC₅₀ of 9.77 ± 2.32 μmol/L, similar to that of cisplatin (IC₅₀=8.96 ± 2.35 μmol/L); 2a also showed a slightly lower nephrotoxicity than cisplatin, and their CC₅₀ was 10.79±0.87 μmol/L and 8.45±0.68 μmol/L, respectively. 2a obviously promoted apoptosis of breast cancer cells in vitro and caused a moderate suppression of the breast cancer growth in the tumor-bearing mouse models without producing serious adverse effects.

CONCLUSIONS

Four compounds synthesized based on imidazo-fused heterocycles have anti-tumor activities against breast cancer. The compound 2a is capable of dose-dependently promoting apoptosis of breast cancer cells in vitro and has a good safety and a moderate efficacy for suppressing tumor growth in mouse models bearing human breast cancer xenografts.

Synthesis and evaluation of the antiproliferative activity of benzylidenes of 16-dehydroprogesterone series

Novel benzylidenes (chalcones) of the 16-dehydroprogesterone series have been characterized and their antitumor activity against two breast cancer cell lines was evaluated. Benzylidenes exhibit significant antiproliferative effect on cells and inhibit cell growth in hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cell lines. Compound 3d exhibits the highest activity against two breast cancer cell lines, with the IC₅₀ value of about 2 µM. Compounds 3e,m,n display considerable selectivity for hormone-dependent breast cancer cells, with the IC₅₀ value lower than 6 µM. Moreover, these steroidal benzylidenes regulate ERα signaling and reveal p53-independent mechanism of pro-apoptotic action in MCF-7 cells. The new class of antitumor compounds holds promise as the basis for the design of agents for cancer therapy.

Synthesis and biological evaluation of estrone 3-O-ether derivatives containing the piperazine moiety

A series of new estrone derivatives were designed and synthesized, and their structures were confirmed by spectroscopic methods. All new estrone derivatives were investigated for their in vitro cytotoxic efficacies against a panel of three human prostate cancer cell lines (PC-3, LNCaP, and DU145). The derivatives 6, 7, 10, 15, 16, 20, 21, 22, 24 and 26 showed important cytotoxic actions against individual carcinoma cell line collections. Moreover, antagonistic activities of compounds (7, 15, 16 and 21) towards a₁-ARs (α_1A, α_1B, and α_1D) were further evaluated using dual-luciferase reporter assays, and the compounds 16 and 21 exhibited better a₁-ARs subtype selectivity. The structure-activity relationship (SAR) suggested that the substitute's type and position on the phenyl group leads to the interesting variations within pharmacological effects of resultant molecular systems.

An Acid-Catalyzed Addition and Dehydration Sequence for the Synthesis of Heteroarylated Steroidal Dienes

Additions of heteroarenes to hormone steroids containing an α,β-unsaturated ketone are reported. Additions of a range of electron-rich heteroarene nucleophiles, including indoles, a pyrrole, and a thiophene, to a variety of commercially available steroids and subsequent dehydration formed 3-heteroarylated steroidal dienes in up to 93% yield. This atom-economical reaction sequence occurs under mild reaction conditions in the presence of catalytic bismuth triflate.

Steroidal Pyrimidines and Dihydrotriazines as Novel Classes of Anticancer Agents against Hormone-Dependent Breast Cancer Cells

Most breast and prostate tumors are hormone-dependent, making it possible to use hormone therapy in patients with these tumors. The design of effective endocrine drugs that block the growth of tumors and have no severe side effects is a challenge. Thereupon, synthetic steroids are promising therapeutic drugs for the treatment of diseases such as hormone-dependent breast and prostate cancers. Here, we describe novel series of steroidal pyrimidines and dihydrotriazines with anticancer activities. A flexible approach to unknown pyrimidine and dihydrotriazine derivatives of steroids with selective control of the heterocyclization pattern is disclosed. A number of 18-nor-5α-androsta-2,13-diene[3,2-d]pyrimidine, androsta-2-ene[3,2-d]pyrimidine, Δ^{1, 3, 5(10)}-estratrieno[16,17-d]pyrimidine, and 17-chloro-16-dihydrotriazine steroids were synthesized by condensations of amidines with β-chlorovinyl aldehydes derived from natural hormones. The synthesized compounds were screened for cytotoxicity against breast cancer cells and showed IC₅₀ values of 7.4 μM and higher. Compounds were tested against prostate cancer cells and exhibited antiproliferative activity with IC₅₀ values of 9.4 μM and higher comparable to that of cisplatin. Lead compound 4a displayed selectivity in ERα-positive breast cancer cells. At 10 μM concentration, this heterosteroid inhibited 50% of the E2-mediated ERα activity and led to partial ERα down-regulation. The ERα reporter assay and immunoblotting were supported by the docking study, which showed the probable binding mode of compound 4a to the estrogen receptor pocket. Thus, heterosteroid 4a proved to be a selective ERα modulator with the highest antiproliferative activity against hormone-dependent breast cancer and can be considered as a candidate for further anticancer drug development. In total, the synthesized heterosteroids may be considered as new promising classes of active anticancer agents.

Triaryl-Substituted Divinyl Ketones Cyclization: Nazarov Reaction versus Friedel-Crafts Electrophilic Substitution

The acid-catalyzed cyclization of a wide range of triaryl-substituted divinyl ketones has been studied. It was found that the reaction pathway strongly depends on the nature of the aryl substituent at the α-position to the carbonyl group. An electron-rich aromatic substituent promotes the reaction to proceed through the intramolecular Friedel-Crafts electrophilic substitution giving dihydronaphthalene derivatives. In contrast, the presence of an electron-deficient substituent is favorable for the Nazarov 4π-conrotatory cyclization yielding triaryl-substituted cyclopentenones. The electrophilic substitution reaction was applied to thiophene and thiazole derivatives.