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

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• . The success of gram-scale reaction and diverse functionalization of isocoumarins demonstrated the synthetic utility of this protocol. Keywords: C–H activation; enaminone; iodonium ylide; isocoumarin; rhodium catalysis; Introduction Isocoumarins are an important structural motif in many naturally

• for the synthesis of isocoumarin scaffolds. Traditional synthetic strategies including 1) intramolecular cyclization of 2-alkenyl benzoic acids or o‑alkynylbenzoates (Scheme 1b, I) [6][7][8][9][10], 2) oxidation of isochromans (Scheme 1b, II) [11][12], or 3) metal-catalyzed cross-coupling/cyclization

• %) as the catalyst, AgSbF6 (10 mol %) and KOAc (50 mol %) as additives in 1,2-dichloroethane (DCE) at 100 °C for 16 hours. To our delight, the desired isocoumarin 3aa was obtained in 42% yield (Table 1, entry 1). Then, the influence of solvents has been subsequently investigated. As a result, DCE proved

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• arylacetylenes 93, 95, and 97 yielded benzofurans 94, benzothiophenes 96, and indoles 98, respectively. When the carbonyl group was introduced between an aryl and a methoxy group (99) then six-membered isocoumarin ring 100 was formed, and when a carbonyl group was introduced in between an aryl and an alkyne

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• sp. 085242 afforded eight isocoumarin derivatives 1–8 and one isoquinoline 9. Asperisocoumarins A and B (1 and 2) were new furoisocoumarins, and asperisocoumarins E and F (5 and 6) were new isocoumarins. Their structures were established by analysis of their spectroscopic data and the absolute

• , respectively. In addition, compounds 1 and 3 exhibited weak radical scavenging activity with EC50 values of 125 and 138 μM, respectively. Keywords: α-glucosidase; Aspergillus; DPPH·; furoisocoumarin; isocoumarin; Introduction Isocoumarins are an important group of natural products with diverse structural

• features and interesting biological activities. They have been widely isolated from fungi, lichens, bacteria, plants, and insects [1][2]. Furoisocoumarins combining a furan ring and an isocoumarin moiety are divided into two subclasses depending on their fusion type: linear furo[2,3-g]isocoumarins and

Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• knowledge there are no reliable synthetic procedures and strategies towards this class of compounds described in the literature so far. The synthesis of the natural glucoside delphoside by Saeed was performed using methyl ether protection at O-6 of the isocoumarin core structure during glucosylation and

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

• Sudipta Pathak,
• Kamalesh Debnath and
• Animesh Pramanik

Beilstein J. Org. Chem. 2013, 9, 2344–2353, doi:10.3762/bjoc.9.269

• starting materials, and the excellent yields of products. Keywords: green chemistry; pyrrole-fused isocoumarin; reusable solid support; silica sulfuric acid; solvent-free condition; Introduction Isocoumarins are an important class of naturally occurring lactones [1][2][3], which has attracted the

• reaction [15], a 6-endo-dig cyclization of heteroaryl esters to alkynes [16], or a Pd(II)-mediated cyclization of o-allylbenzaldehydes [17]. Salvinorin A, a natural product isolated from the hallucinogenic sage Salvia divinorum, which also contains a saturated isocoumarin ring, has been synthesized [18

• ]. Although these methods are useful for the synthesis of isocoumarin derivatives, the reactions involved in the synthesis still suffer from some serious limitations such as the use of expensive and hazardous reagents [12] and toxic metal catalysts [10][11][15][17]. Some of the reactions need laborious and

Gold-catalyzed alkylation of silyl enol ethers with ortho-alkynylbenzoic acid esters

• Haruo Aikawa,
• Tetsuro Kaneko,
• Naoki Asao and
• Yoshinori Yamamoto

Beilstein J. Org. Chem. 2011, 7, 648–652, doi:10.3762/bjoc.7.76

• the results are summarized in Table 1 [18][19][20][21]. With a cationic gold catalyst, derived from Ph3PAuCl and AgClO4, the reaction of 1a with 2a proceeded at 80 °C over 2 h and the benzylated silyl enol ether 3a was obtained in 35% yield, along with the eliminated isocoumarin 4a and recovered 2a in

• , leading to the formation of a cationic intermediate 6 via the intramolecular nucleophilic attack of the carbonyl oxygen on the alkyne as shown in 5. Due to the high leaving ability of the isocoumarin moiety of 6, the silyl enol ether 1 attacks the R group to give the intermediate 7 together with the gold