BF3 Et2O Research Articles

Synthesis and properties of co-oligomers of carbazolyl oxiranes and tetrahydrofuran

Cationically initiated copolymerization of carbazolyl oxiranes—9-(2,3-epoxypropyl)carbazole and 3,6-dibromo-9-(2,3-epoxypropyl)carbazole with tetrahydrofuran has been studied. Reactivity ratios of comonomers have been estimated. Carbazolyl oxiranes are more active monomers in these systems. Kinetics of copolymerization of carbazolyl oxiranes with tetrahydrofuran have been studied by calorimetric technique. The values of reaction orders with respect to concentration of the catalyst BF 3Et 2O and of activation energy have been estimated. Results on photosensitivity of electrophotographic layers based on these copolymers are presented.

Silicon-directed stereocontrolled cyclization. Possible route to functionalized tetrahydrofurans

Cyclization of 3,4,6-tri-O-benzyl-1-deoxy-1-phenyldimethylsilyl-L-glucitol using a slight excess of BF 3Et 2O or a catalytic amount of H 2SO 4 gives access to the 2,5-anhydro-L-glucitol or 2,5-anhydro-L-mannitol derivative, respectively.

A concise synthesis of a benzimidazole analogue of mycophenolic acid using a BF3-Et 2O catalyzed amino-claisen rearrangement.

A nine-step synthesis of the benzimidazole analogue, 2, of mycophenolic acid is reported involving both the BF 3-Et 2O catalysed aromatic amino- and the ortho ester Claisen rearrangements as key steps.

A mild and convenient method for tritium labelling of activated aromatic compounds using BF3–Et2O and tritiated water

A procedure for tritium exchange labelling of activated aromatic compounds using 3H2O and BF3–Et2O has been developed to prepare two radio-labelled photoprobes that are difficult to obtain by conventional methods; the applicability of the method has been examined by labelling several aromatic compounds varying in activation toward electrophilic aromatic substitution.

Asymmetric ring transformation of meso-7-substituted bicyclo[3.3.0]octanones into chiral bicyclo[3.2.1]octene derivatives

Asymmetric ring transformation of meso-7-(2-oxoalkyl)bicyclo[3.3.0]octan-3-ones into chiral bicyclo[3.2.1]oct-2-ene derivatives is accomplished by treatment with chiral cyclic (six- or seven-membered ring) 1,2-diols–BF3–Et2O.

Ipso selectivity in the reductive iodonio-Claisen rearrangement of allenyl(p-methoxyaryl)iodinanes

Allenyl(aryl)iodinanes, generated from p-methoxy(diacetoxyiodo)arenes by the reaction with propyn-2-yl(trimethyl)silanes in the presence of BF3–Et2O in dichloromethane, undergo reductive ipso iodonio-Claisen rearrangement selectivity at –20 °C yielding ipso-substituted propynylarenes.

An efficient preparation of 3-azabicyclo [3.3.0]. Oct-5-en-7-ones from propargyl alcohol- cobalt complexes via nicholas reaction with amidic nitrogen nucleophiles followed by pauson-khand cyclization

3-Azabicyclo [3.3.0]-oct-5-en-7-ones were efficiently prepared from cobalt-propagyl alcohol complexes and various allyl amides via Nicholas reaction in the presence of BF 3Et 2O followed by Pauson-Khand cyclization promoted with trimethylamine N-oxide or SiO 2.

Highly stereoselective boron trifluoride-promoted 5-endo cyclisation of epoxy-allylic stannanes

A novel and highly stereoselective 5-endo cyclisation of epoxy-allylic stannanes 1 promoted by BF3–Et2O has been discovered. The same reaction occurs with lower regio- and stereo-selectivity via an allylic lithium as a result of transmetallation. The selective formation of trans-3-alkenylcyclopentanols is expected to be of importance in terpenoid syntheses.

Stereoselective synthesis of highly labile (Z)-β-alkylvinyl(phenyl)iodonium perchlorates

Labile (Z)-vinyl(phenyl)iodonium perchlorates 2(X = ClO4) were synthesised from (Z)-vinylsilanes 1 by the reaction with (diacetoxyiodo)benzene in the presence of BF3–Et2O in dichloromethane, followed by quenching with aqueous potassium perchlorate solution.

Thermal degradation of 9-(2,3-epoxypropyl)carbazole oligomers

The thermal degradation of oligomers of 9-(2,3-epoxypropyl)carbazole synthesized by the action of anionic (KOH) and cationic (BF 3Et 2O) catalysts has been investigated using the techniques of thermogravimetry, differential thermal analysis (DTA) and gel permeation chromatography (GPC). Kinetic parameters for the process have been determined by two methods. It was shown that the kinetic parameters of the advanced stages of thermal degradation can be correctly determined from the shifts of the peaks of the DTA curves, which occur on changing the heating rate. This cannot be done by conventional methods. It was established by GPC that scission, as well as cross-linking of the oligomer molecules, takes place during the thermal degradation.

Reactions of pennogenin and related compounds. IV. Formation of (25R,22?R,25?R)-3?,3??-diacetoxy-26,22?-epoxy-16,16?-bifurosta-5,20(22),5?,17?(20?)-tetraen-26?-ol from pennogenin diacetate under the action of BF3�Et2O

A new direction of the reaction of pennogenin diacetate with BF3·Et2O has been discovered in which a previously unknown dimeric steroid is formed — (25R,22′R,25′R)-3β,3′β-diacetoxy-26,22′-epoxy-16,16′-bifurosta-5,20(22), 5′,17′(20′)-tetraen-26′-ol, the structure of which has been established as the result of an analysis of IR, UV,1H and13C NMR, and mass spectra. A probable mechanism for the formation of the title compound from pennogenin diacetate is suggested.

ChemInform Abstract: Syntheses of (1.1)Ferrocenylruthenocenophanes and 57Fe‐Moessbauer Spectroscopic Studies of Their Reaction Products with Benzoquinone and BF3·Et2O.

[1.1]Ferrocenylruthenocenophane was prepared by the reduction of [1.1]ferrocenylruthenocenophane-1,12-dione. [1.1]Ferrocenylruthenocenophane and [1.1]ferrocenylruthenocenophane-1,12-dione react with BF3–Et2O containing benzoquinone and give black monocationic salts analyzed as [1.1]ferrocenylruthenocenophanium+BF4− and [1 .1]ferrocenylruthenocenophane-1,12-dionium+BF4−, respectively. 57Fe-Moessbauer spectroscopic studies of the salts suggest the presence of an intramolecular electron transfer between the Ru and Fe atoms.

Syntheses of [1.1]Ferrocenylruthenocenophanes and57Fe-Moessbauer Spectroscopic Studies of Their Reaction Products with Benzoquinone and BF3–Et2O

[1.1]Ferrocenylruthenocenophane was prepared by the reduction of [1.1]ferrocenylruthenocenophane-1,12-dione. [1.1]Ferrocenylruthenocenophane and [1.1]ferrocenylruthenocenophane-1,12-dione react with BF3–Et2O containing benzoquinone and give black monocationic salts analyzed as [1.1]ferrocenylruthenocenophanium+BF4− and [1 .1]ferrocenylruthenocenophane-1,12-dionium+BF4−, respectively. 57Fe-Moessbauer spectroscopic studies of the salts suggest the presence of an intramolecular electron transfer between the Ru and Fe atoms.

Reactions of pennogenin and related compounds. Part 2. Reaction of pennogenin 3,17-diacetate with BF3�Et2O

1. The rearrangement of pennogenin 3,17-diacetate under the action of BF3-Et2O gives the following products: 20S, 22R, 25R-16α, 17α, 22-(1,t 1′, 1′-ethylidenetrioxy)-22,26-epoxycholest-5-ene-3β-ol-3-acetate and 20S, 25R-16α-0.17α-0.23-(1′,1′,1′-ethylidenedioxy-22,26-epoxycholest-5,22-diene-3β-ol-3-acetate. 2. Acetylation of C17α-OH in the 25R-spirostan series leads to anomalously large effects on the values of chemical shifts of the13C(C16) and (H16) nuclei in their13C and1H NMR spectra.

A Protection-Deprotection Method for the Synthesis of Substituted Benzoyloxybenzoates

Abstract Common syntheses of phenyl benzoyloxybenzoates generally produce products in low yields. A variety of synthetic pathways were employed in an attempt to increase the overall yield of the final product. It was found that catalytic agents such as boron trifluoride-etherate (BF3 Et2O), 1,3-dicyclohexylcarbodiimide (DCC), and 4-N, N-di-methylaminopyridine (DMAP) were relatively ineffective in these processes. However. protection of the hydroxy moiety of an appropriately substituted benzoic acid with methyl chloroformate, followed by esterification under normal conditions, and deprotection with ammonia in ethanol produces the hydroxy-benzoyloxybenzoate intermediate. This material can be used in further esterifications to produce phenyl benzoyloxybenzoate compounds in good yield. Materials such as the triply reentrant compound 4-n-nonyloxyphenyl 4-nitrobenzoyloxybenzoate (DB9ONO2) can be prepared by this method.

ChemInform Abstract: HYPERVALENT ORGANOIODINE CHEMISTRY: A NEW SYNTHESIS OF β‐METHYLENE CYCLIC ETHERS

AbstractDurch Behandlung der ungesättigten Trimethylsilylalkohole (I) mit Iodosylbenzol (II) erhält man die cyclischen Methylenether (III).

Preparation of 3,4-dihydroanthracen-1(2H)-ones. A synthetic approach to islandicin and digitopurpone via difluoro[anthracen-1(2H)-onato-O 1,O 9]boron chelates

Three 9,10-dihydroxyanthracen-1(2H)-one derivatives (2a–c) have been obtained by the catalytic hydrogenation of quinizarin, 1-hydroxy-5-methoxyanthraquinone, and 1-hydroxy-8-methoxyanthraquinone, respectively; in the last two reactions, monohydroxyanthracen-1(2H)-ones (4a) and (4b) are formed as by-products. The anthracenone derivatives (2a–c) were O-methylated by methyl toluene-p-sulphonate and the selective demethylation of the dimethoxy derivative (2d) to the monomethoxy derivative (2e) was effected by AlCl3. The silyl enolate (5) was unreactive toward C-methylation but the lithium enolate of the anthracenone (2d) reacted with methyl iodide to give a mixture of C-mono (2f) and C-di (6a) alkylated derivatives; in contrast, the boron enolate of (2d) reacted with methyl iodide to give exclusively the C-monomethylated derivative (2f) and this procedure was extended to the synthesis of 5-methoxy (2g) and 8-methoxy (2h) analogues of (2f). Whereas the dimethoxyanthracenone derivative (2d) is brominated (Br2–CHCl3, 0 °C) in separate reactions to give monobromo (2i) and dibromo (6b) derivatives, the difluoroboron chelate (9a)[from (2d) and BF3–Et2O] was converted by photochemical bromination into a product (9g) of benzylic substitution; the analogue (9h) was similarly obtained from the difluoroboron chelate (9b). The boron derivatives (9g) and (9h) were transformed by methanol into hydroxydimethoxyanthracenone derivatives (2l) and (2m), and (9g) was also converted by wet alumina into the dihydroxymethoxyanthracenone (2n). The hydroxydimethoxyanthracenones (2l) and (2m) were transformed by 2,3-dichloro-5,6-dicyanobenzoquinone [for (2l)] and selenium dioxide [for (2n)] into 1-hydroxy-4-methoxyanthraquinone and 1-hydroxy-4-methoxy-2-methylanthraquinone, respectively.

Preparation of 6α-monosubstituted and 6,6-disubstituted penicillanates from 6-diazopenicillanates: reactions of 6-diazopenicillanates with alcohols, thiols, phenylseleninyl compounds, and allylic sulphides, and their analogues

Reactions of 6-diazopenicillanates (1) and (2) with a range of compounds, in some cases catalysed by BF3–Et2O or Cu(acac)2, have been investigated, and found to be useful for the synthesis of 6α-monosubstituted and 6,6-disubstituted penicillanates. Thus the 6α-alkoxy- and 6α-alkylthio-penicillanates (7)–(15), the 6-phenylselenopenicillanates (26)–(32), and the 6-allyl-6-alkylthio- and 6-ally-6-phenylseleno-penicillanates (39)–(46), were obtained from reactions between 6-diazopenicillanates (1) and (2) and alcohols, thiols, phenylselenol, diphenyl diselenide, phenylseleninyl chloride, allylic sulphides, and allylic selenides. Reactions between 6-diazopenicillanates (1) and (2) and carboxylic acid derivatives and ethers were also briefly examined.The structure of 2,2,2-trichioroethyl 6α-allyl-6β-phenylthiopenicillanate (39) was confirmed by a single-crystal X-ray study.

Hypervalent organoiodine chemistry: a new synthesis of β-methylene cyclic ethers

The allylsilanes (1), containing suitably-substituted hydroxy-groups, on treatment with iodosylbenzene in the presence of BF3–Et2O in an ether solvent, give 5- or 6-membered β-methylene cyclic ehters (3) in good yields, presumably via the highly reactive alylaryliodonium intermediates (2).

SYNTHESIS OF RACEMIC 8-C-PRENYL-6″,6″-DIMETHYLPYRANO(2″, 3″:7,6)NARINGENIN

Abstract Reaction of naringenin (1) with 2-methylbut-3-en-2-ol in the presence of BF3–Et2O gives a mixture of 6-C-prenyl-(5), 8-C-prenyl-(8) and 6,8-di-C,C-prenyl-(2) derivatives. The last compound (2) with DDQ afforded 8-C-prenyl-6″,6″-dimethylpyrano(2″,3″:7,6)naringenin (11) along with its angular isomer (10) in racemic forms.