Synthesis of 3-nitro-3-azalk-2-yl ethers

PrimaryN-nitramines react with vinyl ethers to give 3-nitro-3-azalk-2-yl ethers. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 621–623, March, 1999.     

Synthesis of functionalized arylalkyl and diaryl ethers by [3+3] cyclization of 3-alkoxy- and 3-aryloxy-1-siloxy-1,3-butadienes with 3-(silyloxy)alk-2-en-1-ones

Functionalized diaryl ethers were prepared by [3+3] cyclization of 3-aryloxy-1-siloxy-1,3-butadienes with 3-(silyloxy)alk-2-en-1-ones.     

Comparative photophysical behaviour of naphthalene-linked crown ethers and aza crown ethers of varying cavity dimensions

A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated ligands.     

Synthesis of phthalates and isophthalates by [3+3] cyclizations of 1,3-bis(silyl enol ethers) with 3-(silyloxy)alk-2-en-1-ones

3-Hydroxyphthalates and 4-hydroxyisophthalates were prepared by sequential [3+3] cyclization reactions of 1,3-bis(silyl enol ethers) with 2- and 3-alkoxycarbonyl-3-(silyloxy)alk-2-en-1-ones.     

New methodology for the synthesis of benzoazacrown ethers by transformation of the macrocycle of benzocrown ethers

The review summarizes the results of studies aimed at constructing new promising macrocyclic ligands that bind metal and ammonium ions. A new approach to the synthesis of formyl and nitro derivatives of 1-aza-2,3-benzocrown ethers possessing considerable synthetic potential is described. The review presents a radically new methodology for the synthesis of such benzoazacrown ethers based on stepwise transformations of the macrocycle of readily accessible benzocrown ethers. The main structural factors and necessary conditions enabling stepwise transformations of the macrocycle of crown ethers into azacrown ethers were revealed. For the first time, the ability of N-methylbenzoazacrown ethers to form complexes was found, which is much superior to that of widely used N-phenylazacrown ethers and benzocrown ethers with the same size of the macrocycle.     

Facile one-pot synthesis of aliphatic bridged diaryloxy compounds,cyclic and crown ethers under mild conditions

We report here the facile, room temperature, catalyst free, one pot synthesis of aliphatic bridged diaryloxy compounds, cyclic and crown ethers. Anhydrous potassium carbonate (K₂CO₃) as a mild base along with dimethyl sulfoxide generates the phenoxide ion which facilitates the nucleophilic substitution of bromoalkanes to yield the corresponding crown ethers.     

One-pot synthesis of aryl fluorides by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 2-fluoro-3-silyloxy-2-en-1-ones

Functionalized aryl fluorides were regioselectively prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 2-fluoro-3-silyloxy-2-en-1-ones.     

Dicobalt octacarbonyl-catalyzed cationic polymerization of allylic and enolic ethers

In the presence of silanes bearing Si H groups, dicobalt octacarbonyl [Co₂(CO)₈] efficiently catalyzes the cationic polymerization of a wide variety of enol ether and other related monomers including vinyl ethers, 1-propenyl ethers, 1-butenyl ethers, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, ketene acetals, and allene ethers. In addition, this catalyst system is also effective for the polymerization of complimentary allylic and propargylic ethers by a process involving tandem isomerization and cationic polymerization. This latter process occurs by a stepwise mechanism in which the allylic or propargylic ether is first isomerized, respectively, to the corresponding enol ether or allenic ether and then this latter compound is rapidly cationically polymerized in the presence of the catalyst. In accord with this mechanism, it has been shown that the structure of the polymers prepared from related enol and allyl ethers using the above catalyst system are identical. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1579–1591, 1997     

1-Phenylthio-3-vinyl-3-cyclohexenol, a new reagent for bis-annelation of silyl enol ethers

1-Phenylthio-3-vinyl-cyclohex-1-en-3-ol (2) has been synthesized and investigated as a new bis-annelation reagent for silyl enol ethers. Reagent 2 can be synthesized by a Grignard reaction of vinyl magnesium bromide with 3-phenylthiocyclohexenone. The reaction with silyl enol ethers takes place under Lewis acid catalysis and generally proceeds in good yields. The resulting phenylthiodienes can be hydrolyzed to enones, which have been cyclized in a homologous aldol reaction to polycyclic compounds.     

Solvent-free synthesis of dihydroxy dithiacrown ethers

The solvent-free reaction of oligoethylene glycol diglycidyl ethers with dimercaptoethane in the presence of benzyltrimethylammonium hydroxide (Triton B) gave, via regiospecific epoxide opening reactions, dihydroxy dithiacrown ethers in excellent yields and in short reaction times.     

F-alkylation of bis(allyl) polyoxyethylene ethers

Bis(3-F-alkylallyl) polyoxyethylene ethers were obtained via radical addition of F-alkyl iodides on bis(allyl) ethers CH₂CH(CH₂OCH₂)_nCHCH₂ followed by 1,8-diazabicyclo[5.4.0]undec-7-ne (DBU) dehydrohalogenation.     

Synthesis of functionalized acetophenones by [3 + 3] cyclizations of 1,3-bis-silyl enol ethers with 2-acetyl-3-silyloxyalk-2-en-1-ones

The TiCl₄ mediated cyclization of 1,3-bis-silyl enol ethers with 2-acetyl-1-silyloxybut-1-en-3-one and 3-acetyl-4-silyloxypent-3-en-2-one, readily prepared from 3-formyl(acetylacetone) and triacetylmethane, afforded a variety of functionalized acetophenones.     

A one-pot selective deprotective acetylation of benzyl ethers and OTBDMS ethers using the BF3·Et2O-NaI-Ac2O reagent system

An efficient selective deprotection followed by acetylation of several benzyl ethers, including 6-OBn ethers of monosaccharides, and -OTBDMS ethers has been developed by using the BF₃·Et₂O-NaI-Ac₂O reagent system. In addition, both benzylidene and isopropylidene groups are deprotected to form the corresponding diacetates.     

Synthesis of functionalized 4-chlorophenols and 1,4-dihydroquinones by [3+3] cyclization of 1,3-bis-silyl enol ethers with 2-chloro- and 2-acyloxy-3-(silyloxy)alk-2-en-1-ones

Functionalized 4-chlorophenols and 1,4-dihydroquinones were prepared by [3+3] cyclization of 1,3-bis-silyl enol ethers with 2-chloro- and 2-acyloxy-3-(silyloxy)alk-2-en-1-ones.     

Regioselective synthesis of 2-acetyl- and 2-alkoxycarbonyl-3-(trifluoromethyl)phenols by [3+3] cyclization of 1,3-bis-silyl enol ethers with 4-ethoxy- and 4-silyloxy-1,1,1-trifluoroalk-3-en-2-ones

2-Acetyl- and 2-alkoxycarbonyl-3-(trifluoromethyl)phenols were prepared by [3+3] cyclization of 1,3-bis-silyl enol ethers with 4-ethoxy- and 4-silyloxy-1,1,1-trifluoroalk-3-en-2-ones.     

Synthesis of functionalized p-dihydrobenzoquinones and p-benzoquinones based on [3+3] cyclizations of 1,3-bis-silyl enol ethers

Functionalized mono-protected p-dihydrobenzoquinones were prepared by [3+3] cyclization of 1,3-bis-silyl enol ethers with 2-acyloxy-3-(silyloxy)alk-2-en-1-ones. Deprotection and oxidation of the products afforded the corresponding p-benzoquinones.     

Synthesis of 6-(perfluoroalkyl)salicylates by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-ethoxy-1-(perfluoroalkyl)prop-2-en-1-ones

6-(Perfluoroalkyl)salicylates were prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-ethoxy-1-(perfluoroalkyl)prop-2-en-1-ones.     

Cerium(IV) sulfate tetrahydrate: a catalytic and highly chemoselective deprotection of THP,MOM, and BOM ethers

Tetrahydropyranyl (THP), methoxymethyl (MOM), and benzyloxymethyl (BOM) phenyl/alkyl ethers were efficiently cleaved to the corresponding parent hydroxyl compounds in good yields using catalytic amounts of Ce(SO₄)₂·4H₂O by microwave-assisted or conventional heating in methanol solution. Intramolecular and competitive experiments demonstrated the chemoselective deprotection of THP ethers in the presence of triisopropylsilyl (TIPS) and tert-butyldiphenylsilyl (TBDPS) phenyl ethers.     

Synthesis of novel crown ethers. Part 1. Coumestan and coumestan analog derivatives of crown ethers

The presented ethylenedioxy compounds5a,5d,6a and6c are examples of novel cyclic ethers, while macrocyclic polyethers represent new crown ether analogues. New coumestan-crowns5a-f, derivatives of 6,7-dihydroxy-3,4-dihydro-2H-dibenzofuran-1-one and 6,7-dihydroxy-3,3-dimethyl-3,4-dihydro-2H-dibenzofuran-1-one6a-e were synthesized from the correspondingo-dihydroxy compounds3a-b,4a-b and ditosylates or dichlorides of di- or triethylene glycol in the presence of K₂CO₃, in DMF/H₂O (15/1) solutions at 65–75 °C for 35 hours. The structure of the macrocyclic ethers obtained were confirmed by¹H-NMR,¹³C-NMR, IR spectra and elemental analyses.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Efficient oxidative deprotection of trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers under solvent-free conditions

A mild, efficient and fast method for direct oxidation of trimethylsilyl, tetrahydropyranyl and methoxymethyl ethers to their corresponding carbonyl compounds using trinitratocerium（Ⅳ） bromate （TNCB） supported on NaHSO4.H2O under solvent-free conditions is reported.