Synthesis Of Isocoumarins Research Articles

A short approach to cytogenin and first total synthesis of aspergisocoumarin A and fusarimarin C

A novel, efficient route to the first total synthesis of the bioactive isocoumarins aspergisocoumarin A, fusarimarin C and cytogenin is demonstrated. This approach features a groundbreaking single-step synthesis of isocoumarins utilizing a challenging cross-ester coupling of ethyl dimethoxy orsellinate and ethyl glycolate in the presence of a LiBr-LiTMP complex. The process leverages bromide ion-induced aggregation to facilitate a one-pot tandem reaction sequence: lateral lithiation, acylation, enolization, and lactonization. This innovative method directly produces the isocoumarin moiety with high efficiency. Subsequent transformations include selective BBr3-mediated demethylation, oxidation, and Wittig reactions. The streamlined synthetic routes demonstrated: a two-step pathway to cytogenin and a four-step sequence to aspergisocoumarin A and fusarimarin C, achieving overall yields of 37 %, 27 %, and 27 % respectively.

Non-Kolbe oxidation driven electrochemical C(sp2)–H lactonization towards the synthesis of isocoumarins

A novel method for electrochemical C(sp2)–H lactonization was developed.

Rh(III)-Catalyzed Synthesis of Isocoumarins via C–H Activation of Phenacyl Phosphoniums with Iodonium Ylides

Rh(III)-Catalyzed Synthesis of Isocoumarins via C–H Activation of Phenacyl Phosphoniums with Iodonium Ylides

Copper-Promoted Intramolecular Oxidative Dehydrogenation for Synthesizing Dihydroisocoumarins and Isocoumarins.

Isocoumarins and dihydroisocoumarins are important skeletons with a wide range of biological activities, such as anti-bacterial, anti-allergy, anti-fungal, anti-tumor, and anti-HIV properties. Herein, we demonstrated divergent syntheses of isocoumarins and 3,4-dihydroisocoumarins by intramolecular dehydrogenative cyclization of 2-(3-oxobutyl) benzoic acids. This transformation undergoes Csp3-H bonds and O-H bonds coupling in air using copper salt. The reactions may undergo free radical process.

Water mediated NHC-Pd (II) catalyzed oxidative coupling of benzoic acid and vinylarenes; Selective synthesis of five/six member isocoumarins

Herein, a selective synthesis of isocoumarin and 3-benzylidenephthalides via Heck-type ortho-olefination of benzoic acids with vinyl arenes is reported under the mild reaction protocols. The present reaction was catalyzed by a well-established selenated NHC-Pd(II) pincer complex and Ag(OAc) as an oxidant. All reactions work in water, which is a green eco-friendly solvent; moreover, the method's effectiveness is highlighted by the selective synthesis of isocoumarin or 3-benzylidenephthalides in moderate to good yield. The functional group associated with benzoic acids and vinyl arenes did not exhibit any detrimental effect and displayed the protocol's efficacy. In a nutshell, the present method of oxidative coupling of benzoic acid and vinylarenes entail a lower amount of catalyst and oxidant loading, works effectively with green solvent water, and produces the selective isocoumarin product in 12–14 h under aerobic conditions.

Practical synthesis of isocoumarins via Rh(III)-catalyzed C-H activation/annulation cascade.

Herein, we report an unprecedented Rh(III)-catalyzed C-H activation/annulation cascade of readily available enaminones with iodonium ylides towards the convenient synthesis of isocoumarins. This coupling system proceeds in useful chemical yields (up to 93%) via a cascade C-H activation, Rh-carbenoid migratory insertion and acid-promoted intramolecular annulation. The success of gram-scale reaction and diverse functionalization of isocoumarins demonstrated the synthetic utility of this protocol.

Substrate-directed Synthesis of Isocoumarin and 3-Ylidenephthalide Conjugated Noscapinoids and their Antiproliferative Activities.

A series of new noscapinoids designed; synthesized and assessed whether its 3-ylidenephthalide and isocoumarin conjugates improved cytotoxicity. Cu-catalysed Sonogashira coupling of N-propargyl noscapine with 2-bromobenzoic acids followed by in-situ substrate-directed 5-exo-dig or 6-endo-dig cyclization produced 3-ylidenephthalide 6 a-6 f and isocoumarin 7 a-7 h analogues in very good yields. In comparison to the lead drug, noscapine, all the newly synthesised derivatives exhibited strong cytotoxic potential in vitro with IC50 ranging from 5.4 μM to 39.5 μM across the evaluated panel of cancer cell lines, without harming normal cells (IC50 >300 μM).

Rh(III)-Catalyzed Enaminone-Directed C–H Coupling with Diazodicarbonyls for Skeleton-Divergent Synthesis of Isocoumarins and Naphthalenes

Diversity-oriented synthesis is tremendously useful for expanding the explorable chemical space but restricted by the limited available toolbox of skeleton-diversification chemistry. We report herein Rh(III)-catalyzed coupling of enaminones and diazodicarbonyls for skeleton-divergent synthesis of isocoumarins and naphthalenes. The diazodicarbonyl ring size and pH dependence of the skeleton-forming process demonstrates the achievement of both substrate- and reagent-controlled skeletal diversity generation in a single type of system. An intriguing C-C bond cleavage reactivity is critical for enabling facile synthetic access to isocoumarins.

Synthesis of isocoumarins and PAHs with electron-withdrawing substituents: Impact of the substituent nature on the photophysical behavior

The efficient conditions for rhodium catalyzed oxidative coupling of electron-poor carboxylic acids with diphenylacetylene have been optimized. The best protocol uses Ag2CO3 as an oxidant and DMF as a solvent. The reactions smoothly proceed with the formation of isocoumarins and polycyclic aromatic hydrocarbons (PAHs). The isonicotinic, coumalic, coumarin-3-carboxylic, 4-nitrobenzoic, 4-cyanobenzoic, 4-(ethoxycarbonyl)benzoic, and terephthalic acids were successfully involved in the annulation. In contrast, in the case of picolinic acid, the formation of the stable chelate complex Cp*RhCl(O,N-pic) prohibits the catalytic reaction. The photophysical properties of isocoumarins and PAHs in solutions, such as fluorescence emission and solvatochromic effects, have been studied. In particular, the isocoumarin dyes demonstrate a phenomenon of aggregation-induced emission, while PAHs with electron-withdrawing substituents exhibit strong fluorescence emission in the violet region (370–390 nm) with quantum yields up to 55%.

Fe(III)-catalyzed regioselective and faster synthesis of isocoumarins with 3-oxoalkyl moiety at C-4: Identification of new inhibitors of PDE4

In search of potent and new anti-inflammatory agents, we explored a new class of isocoumarin derivatives possessing the 3-oxoalkyl moiety at C-4 position. These compounds were synthesized via the FeCl3 catalyzed construction of isocoumarin ring. The methodology involved coupling of 2-alkynyl benzamides with alkyl vinyl ketone and proceeded via a regioselective cyclization to give the desired compound as a result of formation of CO and CC bonds. A large number of isocoumarins were synthesized and assessed against PDE4B in vitro. While isocoumarins containing an aminosulfonyl moiety attached to the C-3 aryl ring showed encouraging inhibition of PDE4B, some of the derivatives devoid of aminosulfonyl moiety also showed considerable inhibition. According to the SAR analysis the C6H4NHSO2R2-m moiety at C-3 position of the isocoumarin ring was favorable when the R2 was chosen as an aryl or 2-thienyl group whereas the presence of F or OMe substituent at C-7 of the isocoumarin ring was found to be beneficial. The compound 5f with IC50 values 0.125 ± 0.032 and 0.43 ± 0.013 µM against PDE4B and 4D, respectively was identified as an initial hit. It showed in silico interaction with the PHE678 residue in the CR3 region of PDE4B and relatively less number of interactions with PDE4D. Besides showing the PDE4 selectivity over other PDEs and TNF-α inhibition in vitro the compound 5f at an intraperitoneal dose of 30 mg/kg demonstrated the protective effects against the development of arthritis and potent immunomodulatory activity in adjuvant induced arthritic (AIA) rats. Furthermore, no significant adverse effects were observed for this compound when evaluated in a systematic toxicity (e.g. teratogenicity, hepatotoxicity and cardiotoxicity) studies in zebrafish at various concentrations. Collectively, being a new, potent, moderately selective and safe inhibitor of PDE4B the isocoumarin 5f can be progressed into further pharmacological studies.

Cu(OAc)2 catalyzed ultrasound assisted rapid synthesis of isocoumarin derivatives bearing 3-oxobutyl moiety at C-4 position

A rapid synthesis of isocoumarins has been achieved via the Cu-catalysed cascade reaction involving tandem intramolecular cyclization followed by olefin addition under ultrasound irradiation. The methodology involved one-pot reaction of 2-alkynylbenzoate esters with methyl vinyl ketone in the presence of Cu(OAc)2 in aqueous DMF to afford a range of isocoumarin derivatives bearing 3-oxobutyl moiety at C-4 position. The use of inexpensive, stable and environmentally friendly catalyst along with aqueous media, shorter reaction time and simple operational procedure are the key advantages of this Pd-free methodology. 2009 Elsevier Ltd. All rights reserved.

Recent Advances in the Synthesis of Isocoumarins and Polyaromatic Hydrocarbons for Photoactive Materials

The discovery of transition metal-catalyzed selective activation of aromatic carbon–hydrogen bonds in 1993 has opened a new era in the synthesis of carbo- and heterocyclic compounds. This review covers the applications of oxidative annulations of aromatic compounds with alkynes involving CH activation for the synthesis of isocoumarins and polyaromatic hydrocarbons (PAHs). The limitations, advantages, and mechanical aspects of this approach as well as the current tendencies in the application of the reaction products for photoactive materials are discussed.

Progress in the Chemistry of Amino-Acid Derivatives of Isocoumarins and 3,4-Dihydroisocoumarins

Approaches to the synthesis of isocoumarins and 3,4-dihydroisocoumarins containing natural or synthetic amino-acid fragments are reviewed. Most attention is paid to the two most numerous groups of natural 3,4-dihydroisocoumarins, i.e., ochratoxins and amicoumacins.

Oxime ligands for Pd catalysis of the Mizoroki–Heck reaction, Suzuki–Miyaura coupling & annulation reactions

Monodentate and bidentate chelating oximes are readily available ligands for the Pd catalysis of the Mizoroki–Heck reaction and the Suzuki coupling. High yields were obtained in the Suzuki coupling in aqueous dioxane with TBABr as additive. The oximes can be easily synthesized from the corresponding ketones or aldehydes and thus provide a very large number of nitrogen-based ligands. They have the advantage of not undergoing oxidative degradation, common for phosphine ligands. Chelating oximes with Pd(OAc)2, activate aryl iodides to give high yields of the substitution products in the Mizoroki–Heck reactions as well as the Suzuki coupling. Acetophenone oxime ligand with Pd(OAc)2, catalyzed the reaction of aryl iodides with 1,2-disubstituted alkenes in moderate to high yields. As a test example, the LaRock indole annulation and synthesis of isocoumarin were achieved with acetophenone oxime ligand and Pd(OAc)2 in high yields.

Ruthenium(II)‐Catalyzed C‐H Annulation of Aromatic Acids with Alkynes Using Air as the Sole Oxidant in Water

AbstractA facile synthesis of isocoumarin andα‐pyrones derivatives by Ru(II)‐catalyzed oxidative annulation of aromatic acids and alkynes is reported. This reaction could undergo smoothly in water by use of air as the sole oxidant and accomplishes with the tolerance of a wide range of functional groups. Additionally, the oxidative cyclization of benzoic acid and acrylate is also achieved in the same conditions to furnish the isobenzofuran‐1(3H)‐one scaffold.

Concise Synthesis of Isocoumarins through Rh-Catalyzed Direct Vinylene Annulation: Scope and Mechanistic Insight.

Transition-metal-catalyzed activation of inert C-H bonds and subsequent C-C bond formation have emerged as powerful synthetic tools for the synthesis of elaborate cyclic molecules. In this report, we introduce an efficient synthetic method of 3,4-unsubstituted isocoumarins adopting an electron-deficient CpERh complex as the catalyst. The use of vinylene carbonate as a vinylene transfer reagent enables the direct construction of isocoumarins from readily available benzoic acids, without any external oxidants as well as bases. The reaction mechanism is evaluated by computational analysis to find an unprecedented "rhodium shift" event within the catalytic cycle.

Rhodium(III)-catalyzed chemodivergent annulations between phenyloxazoles and diazos via C–H activation

Acid-controlled, chemodivergent and redox-neutral annulations for the synthesis of isocoumarins and isoquinolinones have been realized via Rh(III)-catalyzed CH activation. Diazo compounds act as a carbene precursor, and coupling occurs in one-pot process, where adipic acid and trimethylacetic acid promote chemodivergent cyclizations.

Carbene Bridging C–H Activation: Facile Isocoumarin Synthesis Through Palladium‐Catalyzed Reaction of 2‐Pseudohalobenzaldehydes with Aryl Diazoesters

A reaction mode on carbene bridging C–H activation (CBA) is described. In this reaction, metal carbene was produced prior to the event of C–H bond metallation. Readily available aryl dizaoesters were employed as the carbene precursors. Migratory insertion of the palladium carbene intermediate could create a modular bridging arm to promote the C–H bond palladation of tethered aldehyde moiety. Its synthetic potential was demonstrated by facile construction isocoumarin scaffold from easily accessible starting materials. Furthermore, this protocol is also amenable for late‐functionalization of complex molecules.

Effect of Cp-Ligand Methylation on Rhodium(III)-Catalyzed Annulations of Aromatic Carboxylic Acids with Alkynes: Synthesis of Isocoumarins and PAHs for Organic Light-Emitting Devices.

An efficient protocol was developed for the synthesis of π-extended isocoumarins and polycyclic aromatic hydrocarbons based on the oxidative coupling of aromatic carboxylic acids with internal alkynes catalyzed by (cyclopentadienyl)rhodium complexes. The coupling chemoselectivity strongly depends on whether Cp or the methylated Cp* ligands are used. The pentamethyl derivative [Cp*RhCl2 ]2 predominantly gives isocoumarins, while the non-methylated complex [CpRhI2 ]n produces naphthalene derivatives. The polyaromatic carboxylic acids (such as 1-naphthoic acid, 1-pyrenecarboxylic acid, fluorene-1-carboxylic acid, and dibenzofuran-4-carboxylic acid) are suitable for this approach. A mixture of Cp*H/RhCl3 can be used as a catalyst instead of [Cp*RhCl2 ]2 . The structures of 3,4-diphenylindeno[1,2-h]isochromen-1(11H)-one and 7,10-dimethyl-8,9-diphenylbenzo[pqr]tetraphene were determined by X-ray diffraction. In addition, the optical properties of the prepared compounds were studied. 7,8-Diphenyl-10H-phenaleno[1,9-gh]isochromen-10-one was employed as an emissive layer for OLED manufacturing. The OLED emits yellow-green light with a maximum intensity 1740 cd ⋅ m-2 at 15 V.

Regioselective cyclization of 2-alkynylbenzoic acid in water for the synthesis of isocoumarin

In this work, a regioselective synthesis of isocoumarins from 2-alkynylbenzoic acid is reported. The transformations proceed smoothly with good yields in water via a metal-free radical pathway. When catalytic TBAB is employed, the reaction provides various isocoumarin derivatives according to the structures of the corresponding precursors. It is believed that TBAB serves as a phase transfer catalyst and radical initiator in the reaction. Compared to previous methodologies, the synthetic procedure reported herein provides a more environmentally benign route for the synthesis of isocoumarins.