Fast Synthesis of Benzofluorenes by Selenium‐Mediated Carbocyclizations

Shahzad, Sohail Anjum; Wirth, Thomas

doi:10.1002/anie.200806148

Cited by 55 publications

(13 citation statements)

References 32 publications

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“…During the development of a new approach towards the synthesis of isocoumarins and dihydroisocoumarins, stilbenecarboxylic acids were synthesized by coupling ofstyrenes with methyl 2‐iodobenzoate 1 using a Mizoroki–Heck reaction providing stilbene esters 2 in good yields 1c,20. The subsequent hydrolysis with lithium hydroxide in the presence of aqueous methanol provided the corresponding carboxylic acids 3 in high yields (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…GP1: General Procedure for the Synthesis of 2‐Substituted Benzoates 2: 1c,20 A mixture of methyl 2‐iodo benzoate (15 mmol, 4.0 g), styrene (18 mmol, 2.1 mL), triethylamine (32 mmol, 4.4 mL), palladium acetate (0.48 mmol, 323 mg) and triphenylphosphane (0.96 mmol, 251 mg) were heated under reflux at 100 °C for 5 h. Solid products were isolated by diluting the reaction mixtures with 10 % hydrochloric acid (200 mL) with stirring to dissolve the salts and excess amine. Finally, the residue was purified by column chromatography (EtOAc/hexane, 1:12) to give products in good yields.…”

Section: Methodsmentioning

confidence: 99%

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Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

2010

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Cyclizations of stilbenecarboxylic acids to the corresponding isocoumarin derivatives using diselenide or disulfide reagents have been developed. By employing bis(triflouroacetoxy)iodobenzene as oxidant for the 6‐endo‐trig cyclizations a variety of dihydroisocoumarins have been prepared in good yields. This method is capable of forming isocoumarins and dihydroisocoumarin derivatives by a cyclization–elimination route.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

2010

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“…Additionally, organoselenium compounds are full of diversity and specialized wide applications such as selenium‐based safety‐catch linkers [13a] for the solid‐phase semisynthesis of vancomycin, asymmetric carboselenylation, [13b] selenocyclizations, [13c] selenium promoted carbocyclization [13d] and acts as catalysts in organic synthesis [13e,f] . Isoselenourea derivatives also show encouraging effects on the antitumor activity (Figure 1).…”

Section: Figurementioning

confidence: 99%

BF₃ ⋅ OEt₂ Catalyzed Synthesis of 1,3‐Thiazines/‐Selenazines

2020

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An efficient strategy for the synthesis of 3,4dihydro-2H-1,3-thiazines / 3,4-dihydro-2H-1,3-selenazines from propargylic alcohols and thioamides/thiosemicarbazones/selenamides is described. The reaction is accomplished in moderate to excellent yield under mild conditions that did not require the exclusion of air or moisture and offers an operationally simplistic and convenient route to the synthetically useful six-membered N,S/Se-heterocycles. 1,3-Thiazines are attractive six-membered N,S-heterocyclic scaffolds for medicinal chemistry. [1] Compounds bearing this subunit often exhibit antiarrhythmic, antispasmodic, angiogenic, and antibiotic activities [2] and are also used as precursors for the preparation of other heterocyclic biomolecules, such as cephalosporins (Figure 1) or 1,4-thiazepines. [3] For example, some derivatives of thiazine are cannabinoid receptor agonists, [4] antihypotensive, [5] antitubercular, [6] and antibacterial [7] agents. Further, thiazine derivatives can be used for gastrointestinal disorders [8] or diabetes [9] prevention. Fused heterocyclic systems possessing thiazine ring have been reported as antioxidants, [10] analgesic, anti-inflammatory agents, [11] or calcium channel modulators. [12] Additionally, organoselenium compounds are full of diversity and specialized wide applications such as selenium-based safety-catch linkers [13a] for the solid-phase semisynthesis of vancomycin, asymmetric carboselenylation, [13b] selenocyclizations, [13c] selenium promoted carbocyclization [13d] and acts as catalysts in organic synthesis. [13e,f] Isoselenourea derivatives also show encouraging effects on the antitumor activity (Figure 1). [14] Selenazines have attracted much attention in dyes [15,16] and medicinal fields (antibacterial effects against Escherichia coli and Staphylococcus aureus, [17] inhibitory effects on the proliferation of human HT-1080 fibrosarcoma cells, [18] protein kinase inhibition, [19] and as antitumor agents [20]). Although syntheses of oxazines [21,22] are well known, but the corresponding thiazines and selenazines have been limited, [23] owing to difficulties in the preparation of sulphur and selenium-containing starting materials. Nevertheless, only a few [a]

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“…Novel double carbocyclizations mediated by selenium were reported by Shahzad and Wirth [81]. Stilbenes 174 were generated from methyl-2-iodobenzoate 173 under palladium-catalyzed Mizoroki-Heck reaction conditions.…”

Section: Metal-mediated Syntheses Of Stilbene Analoguesmentioning

confidence: 99%

Synthetic approaches toward stilbenes and their related structures

2017

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Compounds belonging to the stilbene family have gained remarkable significance in pharmaceutical as well as material chemistry. The current review covers the various synthetic approaches for the syntheses of stilbene scaffold and related structures over last 30 years. In addition, this review also highlights the role of stilbene intermediates used in the synthesis of important molecules with diverse applications in the field of pharmaceutics and material science.

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Fast Synthesis of Benzofluorenes by Selenium‐Mediated Carbocyclizations

Abstract: When one ring is not enough: A new double cyclization of stilbene derivatives results in benzo[b]fluorenes via dihydronaphthalenes. The presence of a selenium electrophile and a Lewis acid are crucial for the formation of the C-C bonds.

Cited by 55 publications

References 32 publications

Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

BF₃ ⋅ OEt₂ Catalyzed Synthesis of 1,3‐Thiazines/‐Selenazines

Synthetic approaches toward stilbenes and their related structures

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Fast Synthesis of Benzofluorenes by Selenium‐Mediated Carbocyclizations

Abstract: When one ring is not enough: A new double cyclization of stilbene derivatives results in benzo[b]fluorenes via dihydronaphthalenes. The presence of a selenium electrophile and a Lewis acid are crucial for the formation of the C-C bonds.

Cited by 55 publications

References 32 publications

Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

Diselenide‐ and Disulfide‐Mediated Synthesis of Isocoumarins

BF3 ⋅ OEt2 Catalyzed Synthesis of 1,3‐Thiazines/‐Selenazines

Synthetic approaches toward stilbenes and their related structures

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BF₃ ⋅ OEt₂ Catalyzed Synthesis of 1,3‐Thiazines/‐Selenazines