Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• precursor for an intramolecular Friedel–Crafts cyclization (Scheme 9) [24]. Therefore, phenylacetaldehyde 52 was converted to the alcohol 53, which was esterified with the α-ketoacid 54 to give ketoester 55. Grignard addition to the keto carbonyl and subsequent TBS deprotection delivered the tertiary

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• .17.140 Abstract The chiral (salen)Cr(III)/BF3·OEt2 catalytic combination was found to be an effective catalyst for intramolecular Friedel–Crafts cyclization of electron-deficient Morita–Baylis–Hillman adducts. In presence of mild reaction conditions the chiral (salen)Cr(III)/BF3·OEt2 complex affords 2

• -substituted-1H-indenes from unique substrates of Morita–Baylis–Hillman adducts via an easy operating practical procedure. Keywords: boron trifluoride etherate; chiral (salen)chromium(III); intramolecular Friedel–Crafts cyclization; Morita–Baylis–Hillman adducts; substituted-1H-indenes; Introduction

• intramolecular Friedel–Crafts cyclization protocol the Morita–Baylis–Hillman adduct 5a, was surveyed as the model substrate. The optimization experiments are listed in Table 1. The cyclization of MBH adduct 5a was examined in presence of metal(III)–salen complex (5 mol %) as catalysts and BF3·OEt2 (2.5 mol %) as

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• oxidation of 1,3-dienes 159 and aroyl-substituted propiolates 160 (Scheme 36) [70]. Subsequently, the authors performed an intramolecular Friedel-Crafts cyclization of the corresponding derivatives 161 by using concentrated sulfuric acid. The authors noted that the more electron-donating alkyl or methoxy

• intermolecular acylation/H2SO4-promoted intramolecular Friedel–Crafts cyclization. The authors prepared substituted anthraquinones bearing Me, OMe, OH, Br, F, or other groups, such as anthraquinones 170a–g, in moderate to good yields (55–69%). The reaction proved efficient mainly with electron-donating

• propiolates followed by intramolecular Friedel-Crafts cyclization. H3PO4-promoted intramolecular cyclization of substituted benzoic acids. Palladium-catalyzed intermolecular direct acylation of aromatic aldehydes and o-iodoesters. Cycloaddition/oxidative aromatization of quinone and β-enamino esters. ʟ

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• . Retrosynthetic analysis of the designed B-ring-modified analogues of brazilin. The synthetic challenge associated with the synthesis of 5 by IFCEA of 6 (above) and recent literature reports of cis-diastereoselective synthesis of related tetracyclic molecules via intramolecular Friedel–Crafts cyclization

• diastereoselectivity (Scheme 2, upper panel). Thus, we were concerned about the possibility of getting a mixture of 5 and 9 under the planned IFCEA cyclization of 6. However, a literature survey indicated that cis-diastereoselective synthesis of related tetracyclic molecules via intramolecular Friedel–Crafts

• cyclization of tetralins (Scheme 2, lower panel) has been described by Lautens and co-workers [27][28]. Nonetheless, a second major issue came to our mind before the synthesis of 5 could be started. The Lewis/Brønsted acidic conditions employed during the IFCEA cyclization might activate the tertiary –OH

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• activation of the cyclopropene 18 also occurred at C2 to afford, after ring-opening, the gold-stabilized allylic cation 24. However, in contrast to the acid-catalyzed reaction, subsequent intramolecular Friedel–Crafts cyclization occurred by nucleophilic attack by the phenyl group (at C2) on the organogold

• proceed through ring-opening and intramolecular Friedel–Crafts cyclization have been studied using 3-aryl-cyclopropene-3-carboxylates. However, for these latter substrates, the carbonyl group can also play the role of a nucleophile and compete with the aryl group. Nucleophilic addition of carbonyl groups