Cyclization of polyfluoro substituted 2-amino- and 2-acetylaminodiaryl ethers into derivatives of phenoxazine

Cyclization of the diaryl ethers 4-RC₅F₄OC₆H₄NH₂(NHAc)-2 (R=C-NO₂, C-CF₃, N), containing an electron accepting group in the fluorinated ring, proceeds in DMF in the presence of K₂CO₃ following a Smiles rearrangement.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 846–849, April, 1990.     

Gold-catalyzed rearrangement of substituted allyl aryl ethers

Triphenylphosphinegold(I) complexes catalyze the Claisen-type rearrangement of aryl allyl ethers to the corresponding branched and linear products. The product distribution depends on the olefin geometry of the allylic ether. Stereochemical transfer experiments support an ionic mechanism.     

An unusual radical Smiles rearrangement

Radicals derived from N-(alpha-xanthyl)acetanilides or N-(alpha-xanthyl)acetylaminopyridines possessing a substituent next to the nitrogen undergo a hitherto undocumented Smiles rearrangement proceeding through a four-membered ring. It was also found that under certain conditions the amidyl radical produced by cleavage of the four-membered ring intermediate can undergo fragmentation to give an isocyanate. Such fragmentations are unprecedented at temperatures corresponding to refluxing benzene or chlorobenzene. [reaction: see text]     

Novel one pot synthesis of 2-amino-4-chloroquinolines via Smiles rearrangement

We have developed a novel one pot synthesis of 4-chloroquinolin-2-ylamines via Smiles rearrangement under milder condition. The key transformation involves O-alkylation of 4-chloro-1H-quinolin-2-ones with chloroacetamide followed by Smiles rearrangement. The scope of this methodology is further extended to the synthesis of 4-chloroquinolin-2-ylmethylamines and 2-(4-chloroquinolin-2-ylamino)ethanols. This methodology has furnished good yields of 2-amino-4-chloroquinolines.     

One-pot conversion of phenols to anilines via Smiles rearrangement

A convenient one-pot synthesis of phenols to anilines using 2-chloroacetamide/K₂CO₃/DMF system catalyzed by KI via Smiles rearrangement has been described. The synthesis of extensive amino aromatic products from phenols containing electron withdrawing group, has been performed in moderate to excellent yields to demonstrate the potentiality of this method in bio-medicinal and pharmaceutical applications.     

A truce on the Smiles rearrangement: revisiting an old reaction--the Truce-Smiles rearrangement

The Smiles rearrangement is the intramolecular nucleophilic aromatic substitution reaction incorporating a heteroatom as the nucleophilic component and an activated electrophilic arene. One particular variation--the Truce-Smiles rearrangement--utilises a carbon-based nucleophile and an electrophilic arene which does not require additional activation. Such a variation generates a new carbon-carbon bond and the synthetic utility of this relatively under-utilised rearrangement is discussed in this tutorial review.     

Smiles rearrangement—XV: The S→N type rearrangement in uracil derivatives

The reaction of 1,3-dimethyl-6-(2-acetamidophenylthio)uracil 6 with caustic alkali followed by methylation gave 1,3-dimethyl-6-(2-methylthioanilino)uracil 7 accompanied with 1,3-dimethyl-5-acetyl-6-(2-methythioanilino)uracil 8. Pyrimido[1,5]benzothiazepine 10 was obtained in high yield by the Smiles rearrangement of 6, trapping of the resulting thiolate ion with formalin and subsequent acid-catalysed cyclization. Treatment of 1,3-dimethyl-6-(2-aminophenylthio)uracil 5 with hot acetic acid gave 1,3-bis[(2-benzothiazolyl)acetyl]-1,3-dimethylurea 12. Upon heating 5 or N-acetyl derivative 6 in dimethylsulfoxide, 5-thiaisoalloxazine 3 was obtained in moderate yield. Mechanisms of the observed reactions were discussed.     

3,3]-Sigmatropic rearrangement/5-exo-dig cyclization reactions of benzyl alkynyl ethers: synthesis of substituted 2-indanones and indenes

Substituted benzyl alkynyl ethers, prepared from the corresponding α-alkoxy ketones in a two-step sequence involving enol triflate formation and KOtBu-induced E2 elimination, undergo [3,3]-sigmatropic rearrangement/intramolecular 5-exo-dig cyclization at 60 °C to form substituted 2-indanones in good overall yields. 1,3-cis-Disubstituted-2-indanones are formed preferentially when the benzylic substituent R(1) is bulky. Substituted indenes may be prepared from 2-indanones in high yields by Horner-Wadsworth-Emmons reaction.     

Trinitroethyl ethers of substituted alcohols

The influence of the trinitromethane salt cations and the substituents in the alkyl moiety of chloromethyl ethers of alcohols on the yields of trinitroethyl ethers of the substituted alcohols formed from them was established. On this basis a representative series of previously unavailable trinitroethanol ethers was synthesized.     

The intramolecular rearrangement of substituted 4-hydroxyhexahydropyrimidine-2-thiones

It has been found that, on being heated with 36% hydrochloric or 85% orthophosphoric acid, substituted 4-hydroxyhexahydropyrimidine-2-thiones (IA) undergo an intramolecular rearrangement connected with the transformation of the cyclic forms IA into the linear tautomers IB and accompanied by dehydration with the formation of substituted 2-alkylamino- or 2-arylamino-4H-1, 3-thiazines.     

Gold(I)-catalyzed Claisen rearrangement of allenyl vinyl ethers; synthesis of substituted 1,3-dienes

Synthesis of substituted 1,3-dienes was achieved via gold(I)-catalyzed Claisen rearrangement of allenyl vinyl ethers. The N-heterocyclic carbene gold chloride catalyst (IPrAuCl) was superior in terms of activity and selectivity and afforded the 3,3-product in excellent yields. A proposed cation-π inter-action played a significant role in affecting the reaction rate.     

Formal [1,3] rearrangement of 2-furylmethyl and 2-thienylmethyl vinyl ethers

Benzyl and naphthylmethyl vinyl ethers are inert in LPDE medium, whereas hetcroaromntic methyl vinyl ethers, viz., 2-furyl and 2-thicnylmelhyl vinyl ethers undergo formal [1,3] rearrangement in LPDE medium.     

Novel [2 + 2] photocycloaddition-induced rearrangement of bichromophoric naphthalene-tethered resorcinol ethers

The first examples of sequential photocycloaddition-rearrangement reactions of naphthalene-tethered resorcinol ethers are described. Bichromophoric aromatic compounds with naphthalene and resorcinol ether moieties were irradiated in the presence/absence of a small amount of acid to give the corresponding cycloaddition-rearrangement products. From the determination of quantum yields, steady-state fluorescence spectral studies, and fluorescence lifetime measurements, the mechanism of this novel photoinduced multistep reaction was elucidated to involve the initial intramolecular exciplex formation, followed by the intramolecular [2 + 2] photocycloaddition between the two aromatic rings and the subsequent acid-catalyzed skeletal rearrangement of the resulting cyclobutane derivative leading to the final products.     

Intramolecular rearrangement of substituted l,2,3,6-tetrahydropyrimidine-2-thiones

The intramolecular rearrangement of substituted 1,2,3,6-tetrahydropyrimidine-2-thiones to the isomeric 2-alkyl(aryl)amino-4H-1,3-thiazines was studied. The rearrangement proceeds in acid media to form the intermediate 4-hydroxyhexahydropyrimidine-2-thiones and their tautomeric 3-oxoalkylthioureas and is accompanied by ring cleavages of the tetrahydropyrimidine-2-thiones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1690–1694, December, 1970.     

Concentration-dependent reactions of deoxofluor with arylglyoxal hydrates: a new route to polyfluoro ethers

[reaction: see text]. In concentrated solutions (CH2Cl2) at 25 degrees C, arylglyoxal hydrates, ArCOCHO*H2O (Ar = 4-MeO-C6H4-, 4-Me-C6H4-, 4-F-C6H4-, Ph-, (2a-f) with Deoxofluor gave fluorinated ethers, ArCF2CHFOCHFCF2Ar, (3a-f) in >90% yields as meso/racemic mixtures (approximately 1:1). Under very dilute conditions, mixtures of ArCF2CHO (major) (4a-f) and ArCF2CF2H (6a-f) (minor) were obtained. The structures of 3b (racemic) and 4a (meso) have been confirmed by single-crystal X-ray analysis.     

Synthesis of substituted aryl enol ethers

A facile route toward substituted aryl diarylvinyl ethers 4 is developed from CuI-mediated cross-coupling reaction of substituted phenols 2 with diarylvinyl bromides 3 in the presence of various bidentate-based ligands in DMF. Skeleton 3 is prepared by Yan’s bromomethylenation of diarylketones 1 with CHBr₃–TiCl₄–Mg in the co-solvent of DME and CH₂Cl₂. The synthetic route obtains moderate yields from the one-step operation and the key structure of 4k is confirmed by X-ray crystallographic analysis. The CADD docking experiments of 4k have been included.