67093-26-9Relevant academic research and scientific papers
General Method for the Synthesis of Phthalaldehydic Acids and Phthalides from o-Bromobenzaldehydes via Ortho-Lithiated Aminoalkoxides
Sinhababu, Achintya K.,Borchardt, Ronald T.
, p. 2356 - 2360 (1983)
A general method for the synthesis of phthalaldehydic acids and phthalides, many of which are key intermediates in natural product synthesis, has been developed. o-Bromobenzaldehydes 1a-f were first protected in situ as α-morpholinoalkoxides by reaction with lithium morpholide.Treatment of the α-morpholinoalkoxides 3a-f with n-butyllithium (to exchange bromine with lithium) followed by sequential treatment with solid CO2 and dilute acid afforded the phthalaldehydic acids 6a-f, respectively.Reduction of 6a-f with NaBH4 in EtOH furnished the phthalides 7a-f, respectively, in nearly quantitative yields.Efficient methods for the synthesis of the o-bromobenzaldehydes 1a-d, which were not readily available, are also described.
9-membered carbocycle formation: Development of distinct friedel-crafts cyclizations and application to a scalable total synthesis of (±)-caraphenol A
Wright, Nathan E.,Snyder, Scott A.
supporting information, p. 3409 - 3413 (2014/04/03)
Explorations into a series of different approaches for 9-membered carbocycle formation have afforded the first reported example of a 9-exo-dig ring closure via a AuIII-promoted reaction between an alkyne and an aryl ring as well as several addi
Polycationic ligands in gold catalysis: Synthesis and applications of extremely π-acidic catalysts
Carreras, Javier,Gopakumar, Gopinadhanpillai,Gu, Liangu,Gimeno, Ana,Linowski, Pawel,Petu?kova, Jekaterina,Thiel, Walter,Alcarazo, Manuel
, p. 18815 - 18823 (2014/01/06)
Very often ligands are anionic or neutral species. Cationic ones are rare, and, when used, the positively charged groups are normally appended to the periphery of the ligand. Here, we describe a dicationic phosphine with no spacer between the phosphorus atom and the two positively charged groups. This structural feature makes its donor ability poorer than that of phosphites and only comparable to extremely toxic or pyrophoric compounds such as PF 3 or P(CF3)3. By exploiting these properties, a new Au catalyst has been developed displaying a dramatically enhanced capacity to activate π-systems. This has been used to synthesize very sterically hindered and naturally occurring 4,5-disubstituted phenanthrenes. The present approach is expected to be applicable to the development and improvement of many other transition metal catalyzed transformations that benefit from extremely strong π-acceptor ligands. The mechanism of selected catalytic transformations has been explored by density functional calculations.
Synthesis and fate of o-carboxybenzophenones in the biosynthesis of aflatoxin
Henry, Kevin M.,Townsend, Craig A.
, p. 3300 - 3309 (2007/10/03)
o-Carboxybenzophenones have long been postulated to be intermediates in the oxidative rearrangement of anthraquinone natural products to xanthones in vivo. Many of these Baeyer-Villiger-like cleavages are believed to be carried out by cytochrome P450 enzymes. In the biosynthesis of the fungal carcinogen, aflatoxin, six cytochromes P450 are encoded by the biosynthetic gene cluster. One of these, AflN, is known to be involved in the conversion of the anthraquinone versicolorin A (3) to the xanthone demethylsterigmatocystin (5) en route to the mycotoxin. An aryl deoxygenation, however, also takes place in this overall transformation and is proposed to be due to the requirement that an NADPH-dependent oxidoreductase, AflM, be active for this process to take place. What is known about other fungal anthraquinone → xanthone conversions is reviewed, notably, the role of the o-carboxybenzophenone sulochrin (25) in geodin (26) biosynthesis. On the basis of mutagenesis experiments in the aflatoxin pathway and these biochemical precedents, total syntheses of a tetrahydroxy-o-carboxybenzophenone bearing a fused tetrahydrobisfuran and its 15-deoxy homologue are described. The key steps of the syntheses entail rearrangement of a 1,2-disubstituted alkene bearing an electron-rich benzene ring under Kikuchi conditions to give the 2-aryl aldehyde 43 followed by silyltriflate closure to a differentially protected dihydrobenzofuran 44. Regiospecific bromination, conversion to the substituted benzoic acid, and condensation with an o-bromobenzyl alcohol gave esters 47 and 50. The latter could be rearranged with strong base, oxidized, and deprotected to the desired o-carboxybenzophenones. These potential biosynthetic intermediates were examined in whole-cell and ground-cell experiments for their ability to support aflatoxin formation in the blocked mutant DIS-1, defective in its ability to synthesize the first intermediate in the pathway, norsolorinic acid. Against expectation, neither of these compounds was converted into aflatoxin under conditions where the anthraquinones versicolorin A and B readily afforded aflatoxins B1 and B2. This outcome is evaluated further in a companion paper appearing later in this journal.
Radical-mediated cyclisation of δ-aryl-β-dicarbonyl compounds to β-tetralones [3,4-dihydronaphthalen-2(1H)-ones]
Jamie, Joanne F.,Rickards, Rodney W.
, p. 2603 - 2613 (2007/10/03)
δ-Aryl-β-dicarbonyl compounds carrying electron-releasing groups in the aromatic ring undergo efficient radical-mediated oxidative cyclisation to β-tetralones in the presence of four equivalents of manganese(III) acetate in acetic acid. Secondary oxidation invariably results in acetoxylation at the benzylic α-position of the initially-formed β-tetralones. Use of the oxidant cerium(IV) ammonium nitrate in methanol affords the corresponding α-methoxylated β-tetralones. The α-acetoxy-α-acyl-β-tetralones, but not their α-acetoxy-α-alkoxycarbonyl analogues, are aromatised in high yield on treatment with alkaline silica gel, providing an effective synthetic entry to appropriately substituted β-naphthols. The possible involvement of such radical-mediated intramolecular annulations of δ-aryl β-diketone intermediates in the biosynthetic formation of the second carbocyclic ring of the naphthalenoid ansamycin antibiotics is discussed in relation to the previously proposed Michael addition mechanism.
ARYLATION OF 1-TRIBUTYLSTANNYL GLYCALS CATALYZED BY PALLADIUM: A SYNTHETIC ROUTE TO THE BASIC SKELETON OF THE PAPULACANDINS AND CHAETIACANDIN
Dubois, Eric,Beau, Jean-Marie
, p. 5165 - 5168 (2007/10/02)
The palladium-catalyzed coupling reaction of 4,6-O-benzylidene-3-O-tert-butyldimethylsilyl-1-tri-n-butylstannyl-D-glucal 7 with 3,5-dibenzyloxy-2-bromo-benzyl alcohol 8 gave a 78percent yield of the C-arylated glycal 11, stereoselectivity transformed into
