Reaction of echinochrome trimethyl ether with aqueous ammonia

Reaction of 7-ethyl-2,3,6-trimethoxynaphthazarin with NH₃·H₂O proceeds at the carbonyl groups at the C(4) atoms of the 1,4-naphthoquinonoid tautomeric forms. Methoxy group adjacent to ethyl group is the orienting substituent in this reaction.     

Meroterpenoids—IV : Acid-catalyzed cyclization of bakuchiol methyl ether

Bakuchiol methyl ether cyclizes on acid catalysis to give two major products, which have been suitably correlated. Stereochemistry of these products in relation to the preferred conformations of the transition state is discussed. Direct Wolff-Kishner reduction of ‘ozonides’ is described.     

Flavanoids-IV-stereochemistry of cyanomaclurin : Synthesis of trimethyl ether of (±) epicyanomaclurin

Stereochemistry of cyanomaclurin is confirmed by a stereospecific synthesis of (±) epicyanomaclurin trimethyl ether and the solvolysis of its mesylate to the former. The earlier prediction that the dihydropyran protons should have small coupling in both the isomers in this cage structure is also confirmed.     

Synthesis of bastadin-6 trimethyl ether,a novel 28-membered ring lactam

Bastadin-6 trimethyl ether, a 28-membered ring lactam, was synthesized by means of phenolic exidation of dibromobastadin-2 trimethyl ether with thallium (III0 nitrate (TTN) leading to the formation of the corresponding macrocyclic biphenyl ether as a key step. From bastadin-2 trimethyl ether, a 26-membered ring compound was also synthesized.     

A modular synthesis of the lamellarins: total synthesis of lamellarin G trimethyl ether

A modular synthesis of the lamellarin family of natural products has been developed that is based on the application of three iterative halogenation/cross-coupling reaction sequences. The ability to halogenate the pyrrole core in a regioselective fashion, even in the presence of highly electron-rich aryl substituents, has been established. The compatibility of Suzuki coupling conditions with free alcohols and phenols in the boronic acids has been employed to reduce the number of protection/deprotection steps. Indeed, the presence of a free phenol on boronic acid 3 has been determined to be critical for the successful final coupling in route to lamellarin G trimethyl ether, since protected versions fail to undergo coupling.     

Chemistry of the podocarpaceae—X Synthesis of podospicatin and its trimethyl ether

Podospicatin (I) and its trimethyl ether (II) have been synthesized by separate standard procedures respectively, involving in the former a rearrangement with alkali.     

Synthesis of lamellarin U and lamellarin G trimethyl ether by alkylation of a deprotonated alpha-aminonitrile

1,2,3,4-Tetrahydroisoquinoline-1-carbonitriles can serve as starting materials for the one-pot synthesis of 5,6-dihydropyrrolo[2,1 a]isoquinolines and 1-benzyl-3,4-dihydroisoquinolines. The latter compounds were transformed to lamellarin G trimethyl ether and lamellarin U in short reaction sequences. This method allows the introduction of acid-sensitive protecting groups for the phenolic hydroxy functions which would be cleaved under the harsh conditions of the classical Bischler-Napieralski reaction.     

Dimerization of resveratrol trimethyl ether by phosphotungstic acid, structure confirmation of resformicol A and B

Dimerization of the trimethyl ether of resveratrol catalyzed by phosphotungstic acid gave two tetralins and a naphthalene derivative. The structure of the tetralins was obtained by X-ray crystallography and confirms the reported stereochemical configuration of resformicol A and B.     

Acid-catalyzed polycondensation of bisdiazoalkanes

Dimerization reactions of diphenyldiazomethane have been applied to the polycondensation of six bisdiazobenzyl arylenes, namely 1,4- and 1,3-bis(α-diazobenzyl)-benzenes C₆H₅CN₂? (C₆H₄)? CN₂C₆H₅; 1,4- and 1,3-bis(α-diazo-p-methoxybenzyl)-benzenes, p,p′-MeO? C₆H₄? CN₂? (C₆H₄)? CN₂C₆H₄? OMe; 4,4′-bis(α-diazobenzyl)-diphenylmethane, C₆H₅CN₂? (C₆H₄CH₂C₆H₄)? CN₂C₆H₅; and 4,4′-bis(α-diazobenyl)-diphenyl ether, C₆H₅CN₂? (C₆H₄? O? C₆H₄)CN₂C₆H₅. Depending on the nature of the catalysts, polyene-arylenes (? C(Ar)?C(Ar)? C₆H₄)_n, and polyazine-arylenes, (? C(Ar)?N? N? C(Ar)? C₆H₄? )_n, can be obtained selectively by acid-catalyzed decomposition of these bisdiazoalkanes at room temperature. With perchloric acid and with arylsulfonic acids in strong polar media, polyene-arylenes are formed. On the other hand, boron trifluoride and arylsulfonic acids in solvents of low dielectric constant afford polyazine-arylenes. Less selective is the thermal decomposition at 75°C in toluene solution; it gives a polymer containing about 90% azine and 10% olefinic groups. All these polymers are soluble in common solvents. Their molecular weight vary from 3 200 to 5 000, i.e., X?_n from 12 to 20. The polyene-arylenes are very stable and decompose only around 500°C; the polyazine-arylenes are less stable and decompose around 370°C by losing nitrogen.     

Squaric acid ester-based total synthesis of echinochrome A

The total synthesis of echinochrome A is described. Both key intermediates 5 and 8 were efficiently prepared from diisopropyl squarate 7. Nucleophilic addition of aryllithium 8 to 5, followed by thermal ring-expansion/cyclization of the 1,2-adduct 4, furnished hydroquinone 3. Oxidation and full deprotection of 3 gave the title compound.     

Regioselectivity in lithiation of t-butyldimethylsiloxy-3, 5-dimethoxybenzene. A synthesis of the trimethyl ether of sophoraflavanone A

Selective metallation by inhibiting the directive effect of an oxygen substituent leads to selective substitution of a trioxygenated benzene and a five step synthesis of the titled potentially anti-fungal natural product.     

Acid-catalyzed opening of 3,4-epoxycaranones

Conclusions -3,4-Epoxy-2-caranone and-3,4-epoxy-5-caranone when treated with MeOH in acid medium undergo rearrangement of the bicyclo[4.1.0]heptane structure to the menthane structure, which was observed previously in the reactions with HCl. The mechanism of the acid-catalyzed opening of 3,4-epoxycaranones is discussed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 698–700, March, 1982.     

Acid-catalyzed rearrangement of fused alkylideneoxetanols

Complex aza-fuzed tricyclic lactones are obtained in a two-step photochemical cycloaddition/acid-catalyzed rearrangement of simple alkoxy maleimide derivatives. The sequence involves a complex acid-catalyzed skeletal rearrangement of the intermediate alkylideneoxetanols.