Catalytic Amount Of BF3 Research Articles

Regiodivergent DH or HD Addition to Alkenes: Deuterohydrogenation versus Hydrodeuterogenation.

The regioselective and regiodivergent addition of H-D to a variety of 1,1-diarylalkenes was realized utilizing selectively deuterated dihydroaromatic compounds, which were generated by cobalt catalysis. The reaction was initiated by catalytic amounts of BF3·Et2O by abstracting hydride or deuteride ions from the respective dihydroaromatic reducing agents and led to a highly regioselective incorporation of deuterium and hydrogen at the desired positions of the starting material.

The synthesis of a hexameric expanded hemiporphyrazine

Although the chemistry of expanded porphyrins is well developed, there has been significantly less work on expanded isoindoline based macrocycles such as hemiporphyrazines. In this report we present the synthesis and characterization of a new hexameric expanded hemiporphyrazine which we refer to as hexahemiporphyrazine. The synthesis incorporated bis(6-amino-2-pyridyl)amine as a starting material, which could be produced from 2,6-diaminopyridine using melt reaction conditions. Bis(6-amino-2-pyridyl)amine can adopt a three different conformations, two of which are observed in the free base and protonated form, and the third in the backbone of hexahemiporphyrazine. Reaction of bis(6-amino-2-pyridyl)amine and diiminoisoindoline in the presence of a catalytic amount of BF3 produces the hexihemiporphyrazine macrocycle, which was characterized spectroscopically and by X-ray crystallography. Structure elucidation reveals two inverted pyridine rings in a configuration reminiscent of that seen in hexaphyrin, however hexahemiporphyrazine lacks cross conjugation across the macrocycle.

Novel protocol for the synthesis of octahydropyrano- and thiopyrano[4,3-a]carbazole derivatives via Prins/Friedel–Crafts cyclization

A novel Prins/Friedel–Crafts cyclization of (Z)-6-(1-methyl-1H-indol-3-yl)hex-3-en-1-ol with aldehydes has been achieved using a catalytic amount of BF3·OEt2 under mild reaction conditions to produce the corresponding octahydropyrano[4,3-a]carbazole derivatives in good yields with high diastereoselectivity. The cross-coupling of (Z)-6-(1-methyl-1H-indol-3-yl)hex-3-ene-1-thiol with aldehydes affords the corresponding octahydrothiopyrano[4,3-a]carbazole derivatives under similar conditions.

ChemInform Abstract: BF3·OEt2‐Catalyzed Tandem Prins Friedel—Crafts Reaction: A Novel Synthesis of Sugar Fused Diarylhexahydro‐2H‐furo[3,2‐b]pyrans.

d-Glucose based homoallylic alcohol reacts smoothly with various aldehydes in the presence of arenes and a catalytic amount of BF3·OEt2 under mild conditions to afford a novel series of 5,7-diaryl-hexahydro-2H-furo[3,2-b]pyrans in good yields with high cis-selectivity.

Thioglycosylation of 1,2- cis-glycosyl acetates: a long-standing overlooked issue in preparative carbohydrate chemistry

1,2- cis-Glycosyl acetates with the α-configuration were revealed to be very unreactive towards Lewis acid catalyzed thioglycosylations. Optimal and cost-effective conditions for enabling this direct conversion is absent in the literature. Our studies have shown that elevating the reaction temperature with a catalytic amount of BF 3·OEt 2 was more effective than changing Lewis acids with higher acidities to accommodate the low reactivity of α-glycosyl acetates. The effect of impurities in stored BF 3·OEt 2 on the reaction is also discussed.

BF 3·OEt 2-catalyzed tandem Prins Friedel–Crafts reaction: a novel synthesis of sugar fused diarylhexahydro-2 H-furo[3,2- b]pyrans

d-Glucose based homoallylic alcohol reacts smoothly with various aldehydes in the presence of arenes and a catalytic amount of BF 3·OEt 2 under mild conditions to afford a novel series of 5,7-diaryl-hexahydro-2 H-furo[3,2- b]pyrans in good yields with high cis-selectivity.

Three-Coordinate NiII: Tracing the Origin of an Unusual, Facile Si−C(sp3) Bond Cleavage in [(tBu2PCH2SiMe2)2N]Ni+

All attempts to synthesize (PNP)Ni(OTf) form instead ((t)Bu(2)PCH(2)SiMe(2)NSiMe(2)OTf)Ni(CH(2)P(t)Bu(2)). Abstraction of F(-) from (PNP)NiF by even a catalytic amount of BF(3) causes rearrangement of the (transient) (PNP)Ni(+) to analogous ring-opened [((t)Bu(2)PCH(2)SiMe(2)NSiMe(2)F)]Ni(CH(2)P(t)Bu(2)). Abstraction of Cl(-) from (PNP)NiCl with NaB(C(6)H(3)(CF(3))(2))(4) in CH(2)Cl(2) or C(6)H(5)F gives (PNP)NiB(C(6)H(3)(CF(3))(2))(4), the key intermediate in these reactions is (PNP)Ni(+), [(PNP)Ni](+), in which one Si-C bond (together with N and two P) donates to Ni. This makes this Si-C bond subject to nucleophilic attack by F(-), triflate, and alkoxide/ether (from THF). This σ(Si-C) complex binds CO in the time of mixing and also binds chloride, both at nickel. Evidence is offered of a "self-healing" process, where the broken Si-C bond can be reformed in an equilibrium process. (PNP)Ni(+) reacts rapidly with H(2) to give (PN(H)P)NiH(+), which can be deprotonated to form (PNP)NiH. A variety of nucleophilic attacks (and THF polymerization) on the coordinated Si-C bond are envisioned to occur perpendicular to the Si-C bond, based on the character of the LUMO of (PNP)Ni(+).

Synthesis and Properties of a Photoactivatable Analogue of Psychosine (β‐Galactosylsphingosine)

Synthesis and Properties of a Photoactivatable Analogue of Psychosine (β‐Galactosylsphingosine)

The allylic nucleophilic substitution of Morita–Baylis–Hillman acetates with isocyanides: a facile synthesis of trisubstituted olefins

Abstract Morita–Baylis–Hillman acetates undergo smooth allylic nucleophilic substitution (S N 2′) with tosylmethyl isocyanide (TosMIC) in the presence of a catalytic amount of BF 3 ·OEt 2 under mild conditions to furnish trisubstituted olefins in high yields with ( E )-stereoselectivity.

The acid-promoted reactions of phenyliodonium ylides with substituted anilines and their applications to the synthesis of indoles

The N-substituted anilines 1 react readily with phenyliodonium ylides 2 derived from 1,3-dicarbonyl compounds in the presence of a catalytic amount of BF(3).Et(2)O, forming the C-N coupling products 3, which are precursors for the synthesis of indoles. On the basis of this result, the direct synthesis of indoles from 1 and 2 under thermal conditions and photochemical conditions was explored. The transformations could be achieved in a one-pot way under thermal conditions or in a tandem manner under photochemical conditions.

Heterocyclization of N-propenyl-substituted phenothiazines and phenoxazines using electrophiles in an anhydrous medium

10-Propenylphenothiazine reacts with a catalytic amount of BF3·Et2O in dry ethyl acetate via intramolecular heterocyclization of an intermediate dimeric cation to give mainly 1-ethyl-2-methyl-3-(phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-k,l]phenothiazine and a minor product through fission of phenothiazine which is 1-ethyl-2-methyl-1H-pyrido[3,2,1-k,l]phenothiazine. Under similar conditions 10-propenylphenoxazine gave an oligomer (degree of polymerization 4.4) and the minor product 1-ethyl-2-methyl-1H-pyrido[3,2,1-k,l]phenoxazine likely formed similarly to the phenothiazine analog from the corresponding product of intramolecular heterocyclization (the latter not being observed in the reaction mixture).

A Practical Route to 2,3-Di-/1,2,3-Trisubstituted Indolizines from α-EWG Ketene S,S-Acetals and Their Application in Bis(1-indolizinyl)methane Synthesis

An easy synthesis of 2,3-di-/1,2,3-trisubstituted indo-l-izines has been developed via a formal [3+2] annulation of α-EWG ketene S, S-acetals with 2-pyridine-/2-quinolinecarbaldehyde. The disubstituted products are formed via an intramolecular aza-Michael- addition and subsequent elimination of acetic acid, followed by desulfenylation- assisted by acetic acid, whereas the trisubstituted products are obtained via a similar conjugate addition followed by elimination of alkanethiol. This strategy has been applied to the synthesis of bis(1-indolizinyl)methanes by the condensation of a 2,3-disubstituted indolizine with aldehydes/ketones in the presence of a catalytic amount of BF 3 ·OEt 2 .

Difluorocarbene Chemistry: A Simple Transformation of 3,3‐gem‐Difluorocyclopropenes to Cyclopropenones.

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Difluorocarbene Chemistry: A Simple Transformation of 3,3‐gem‐Difluorocyclopropenes to Cyclopropenones†

AbstractThe cycloaddition reactions of α‐acetyoxyl propynes with difluorocarbene, generated from the decomposition of FSO2CF2CO2SiMe3 in DG in the presence of 10% of NaF at 120 °C gave readily α‐acetyoxyl gem‐difluorocyclopropenes. When these fluorinated compounds were hydrolyzed under alkaline condition at 0 °C, α‐hydroxyl cyclopropenones were produced predominantly whereas treated with catalytic amounts of BF3·Et2O in Et2O, α‐acetyoxyl cyclopropenones were obtained.

Synthesis of dihydroxyphenacyl glycosides for biological and medicinal study: β-oxoacteoside from Paulownia tomentosa

The protected structure of β-oxoacteoside (tomentoside A), 2-oxo-2-(3,4-dihydroxyphenyl)ethyl 3-O-(2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-4-O-caffeoyl-β-d-glucopyranoside 14 was synthesized in 14% overall yield in 11 steps, starting from d-glucose for biological and medicinal studies of phenylpropanoid glycosides. The first step was the preparation of a 3-O-rhamnopyranosyl disaccharide sugar core 2 from a suitably protected rhamnosyl trichloroacetimidate 10 and glucose derivative (diacetone-d-glucose 1) in 71% yield. To the glucose moiety of this sugar core, several protection/deprotection procedures were performed sequentially to obtain a fully acetylated sugar core 7 with a 4-OH group on the glucose moiety, in 57% yield in five steps. Thereafter, to the 4-OH group of the glucose moiety, selective 4-O-caffeoylation was achieved by proton-transfer esterification with 3,4-di-O-allylcaffeic acid 16 to give the caffeoyl disaccharide 11 in 97% yield. Then, it was converted to trichloroacetimidate 13 for a glycosylation donor in 90% in two steps. Finally, anomeric glycosylation was conducted with 2-oxo-2-(3,4-di-allyloxyphenyl)ethyl alcohol 19 with catalytic amounts of BF3·Et2O to give 2-oxo-2-(3,4-di-allyloxyphenyl)ethyl 2,6-di-O-acetyl-3-O-(2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl)-4-O-(3,4-di-allyloxycaffeoyl)-β-d-glucopyranoside 14 in 60% yield. Deprotected intermediates of compounds 2, 11, 14, and 19 which were obtained in high yield would be useful for biological and medicinal studies of phenylpropanoid glycosides.

Microwave‐Assisted Methylation of Carboxylic Acids and Phenolic Compounds with Dimethyl‐Carbonate Under Solvent‐Free Condition

Phenolic compounds and carboxylic acids are methylated with dimethyl carbonate in the presence of a catalytic amount of BF3 · OEt2, DBU, or KOH, in good to excellent yields under microwave irradiation and solvent‐free conditions.

Total synthesis of flavocommelin, a component of the blue supramolecular pigment from Commelina communis, on the basis of direct 6-C-glycosylation of flavan.

We succeeded in a first total synthesis of flavocommelin (1), a component of the blue supramolecular pigment, commelinin (2), from Commelina communis, by direct 6-C-glycosylation of the flavan 4 using perbenzylglucosyl fluoride 8 in the presence of MS 5 angstroms in CH2Cl2 and a catalytic amount of BF3 x Et2O. After 6-C-glycosylation of 4, oxidation with CAN to flavanone 18 and subsequent 4'-O-glycosylation, promoted with a combination of BF3 x Et2O and DTBMP, afforded diglucosylflavanone 20. DDQ oxidation of 20 and deprotection successively gave 1.

Co2(CO)8-mediated endo mode cyclization of epoxy-alcohol: synthesis of 2-ethynyl-3-hydroxy-2-methyltetrahydropyran and 2-ethynyl-3-hydroxy-3-methyltetrahydropyran derivatives.

Successive treatment of 4,5-epoxy-5-methyl-7-trimethylsilyl-6-heptyne-1-ol with Co2(CO)8 at 0 degrees C and a catalytic amount of BF3 x OEt2 at -78 degrees C gave the tetrahydropyran derivatives with the cobalt-complexed moiety. Similarly 4,5-epoxy-4-methyl-7-trimethylsilyl-6-heptyne-1-ol underwent ring closure under the above conditions to provide the corresponding tetrahydropyran derivatives. The preferential endo mode cyclization over the exo one was observed in these experiments.

Functionally substituted sulfur-containing compounds

Reactions of 2-[(organylthio)methyl]oxiranes with aliphatic alcohols in the presence of catalytic amounts of BF3·Et2O are accompanied by 1,2-migration of the organylthio group to give mixtures of 2-alkoxy-3-(organylthio)propan-1-ols and 3-alkoxy-2-(organylthio)propan-1-ols. The ratio of these isomers is significantly influenced by the structure of the alcohol and the nature of the organylthio group. The proposed reaction mechanism includes the formation of a thiiranium intermediate and its subsequent transformations.

Tungsten Carbonyl Complexes of 1H-Diphosphirenes and Diphosphirenylium Salts

The 1,1,3-tris(diisopropylamino)diphosphirenium salt 1 reacts with lithium aluminium hydride leading to the P-hydrogeno-C-phosphinophosphaalkenes 2, which on treatment with a catalytic amount of BF3·OEt2 afford the 1,3-bis(diisopropylamino)-1H-diphosphirene 3. The corresponding η1-coordinated 1H-diphosphirene 6 can be prepared by treatment of 2 or 3 with one equivalent of [W(CO)5(thf)]. Alternatively, the diphosphirenium salt 1 reacts with an excess of [W(CO)5(thf)], affording the corresponding η1-coordinated diphosphirenium salt complex 4, which is converted into the P-hydrogenophosphaalkene complex 5 with lithium aluminium hydride. The dinuclear tungsten complexes 7 and 8 are obtained by treatment of the free 1H-diphosphirene 3 with two equivalents of [W(CO)5(thf)] or one equivalent of [W(CO)4(thf)2], respectively. Compound 6 reacts with two equivalents of hydrogen chloride, giving the 1-chloro-3-diisopropylamino-1H-diphosphirene 9, which can be subsequently converted into the 1-diisopropylamino-, 1-azido, or 1-phenyl-3-diisopropylamino-1H-diphosphirenes 6, 10 and 11 by nucleophilic substitution with diisopropylamine, azidotrimethylsilane or sodium tetraphenylborate, respectively. The [η2-(3-diisopropylaminodiphosphirenylium salt)·W(CO)5] complexes 12a-c can be prepared by reaction of 9 with silver trifluoromethanesulfonate, aluminium or gallium trichloride or, alternatively, by treatment of 6 with two equivalents of trifluoromethanesulfonic acid. Reaction of 12a with diisopropylamine, water, bis(triphenylphosphoranylidene)ammonium chloride or tetrabutylammonium fluoride gives the corresponding 1H-diphosphirene complexes 6, 13, 9, or 14, respectively. Compound 12a also reacts with one or two equivalents of [W(CO)5(thf)], leading to the di- and tri-nuclear complexes 15and 16, respectively.