Synthesis and polymerizations of methyl 3,3-difluorocyclobutene-1-carboxylate and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate

Two new monomers, methyl 3,3-difluorocyclobutene-1-carboxylate (MDFC) and methyl 3,3,4,4-tetrafluorocyclobutene-1-carboxylate (MTFC), were synthesized. Under free radical conditions, MDFC gave homopolymer; MTFC did not. Copolymerizations of these monomers showed them to behave as very electron-deficient monomers, MTFC more so than MDFC. MDFC copolymerized with various vinyl ethers and styrenes to give high yields of almost 1:1 copolymers. Acrylonitrile copolymerized in lower yield with less incorporation of MDFC; trimethylethylenetricarboxylate did not copolymerize. Bicyclobutane-1-carbonitrile copolymerized well. MTFC copolymerized with the very electron-rich monomers t-butyl vinyl ether and p-methoxystyrene, leading to alternating and nearly alternating copolymers, respectively, and even styrene tended to give almost 1:1 copolymers. Acrylonitrile gave only polyacrylonitrile, and trimethylethylenetricarboxylate did not react with MTFC under free radical conditions. The reaction of MTFC with the electron-rich monomers t-butyl vinyl ether and p-methoxystyrene occurred spontaneously via charge transfer complexes. Thermally, the copolymers were rather stable, those of MTFC more so than those of MDFC.     

Syntheses of methyl α-dl-mycaminoside, methyl α-dl-oleandroside, methyl β-dl-cymaroside, methyl α-dl-tyveloside and methyl α-dl-chromoside C

Five rare hexoses, which are components of antibiotics or cardiac glycosides, have been synthesized as methyl glycosides through a common intermediate methyl 2,3-dehydro-2,3,6-trideoxy-α-dl glucopyranoside (7). Epoxidation and subsequent treatment with dimethylamine of7 afforded methyl α-dl-mycaminoside (9). The addition reaction of MeOH to12 gave methyl α-dl-oleandroside (15) and methyl β-dl-cymaroside (17). The hydroxymercuration and subsequent reduction of12 afforded methyl α-dl-chromoside C (19) and methyl β-dl-tyveloside (25).     

Conductance of 1∶1 electrolytes in methyl acetate

The electrolytic conductances of NaClO₄, NaB(C₆H₅)₄, (n-C₄H₉)₄NClO₄ and (n-C₄H₉)₄NPF₆ have been measured in methyl acetate at 25°C. A dominating feature of these electrolyte solutions is, as expected, strong ion pairing. In addition it is found that the formation of triple ions makes an important contribution to the overall molar conductivities. The data suggest that there are strong ion-solvent interactions leading to structure-enhanced (after Diamond) ion association and triple ion formation which has an exact analogy in the phenomena of salting-in. The effects of increasing solution permittivity and viscosity are discussed, particularly in regard to comparing two models of treating conductivity data. The first model includes ion pairs and triple ions, and the second model ignores triple ion formation ascribing the anomalous increase in molar conductivities to a decrease in the ion association equilibrium constant caused by increasing solution permittivity.     

Conductance of 1:1 electrolytes in methyl formate

The electrolytic conductivities of LiClO₄, LiAlCl₄, LiAsF₆, NaClO₄, NaBPh₄, and Bu₄NClO₄ have been measured in methyl formate at 25°C. Evidence is presented for strong association between the perchlorate ion and the formyl proton of the solvent. Ion association and triple ion formation constants suggest that LiClO₄, LiAlCl₄, and NaClO₄ form solvent separate ion pairs and triple ions. NaBPh₄ forms contact ion pairs and triple ions, and the remaining salts appear to form both types of ion pairs and triple ions.     

Radical copolymerization of acrylic monomers. VIII. Copolymerization of methyl methacrylate with methyl α-p-chlorobenzylacrylate and methyl methacrylate with methyl α-p-methoxybenzylacrylate

Free-radical copolymerization of methyl methacrylate with methyl α-p-chlorobenzylacrylate and methyl methacrylate with methyl α-p-methoxybenzylacrylate have been studied in benzene solution at 40°C. Although a simple copolymerization model fits the composition data, the kinetic behavior of both copolymerization systems are analyzed from simple and reversible copolymerization models, taking into account the relatively low ceiling temperature of both methyl α-(p-substituted benzyl)acrylates and considering that the overall rate of copolymerization drastically decreases with the increase of the corresponding methyl α-(p-substituted benzyl)acrylate molar fraction in the feed.     

Direct conversion of 1-deoxy-1-nitroalditols to methyl glycofuranosides

Treatment of the sodium nitronate forms of 1-deoxy-1-nitrohexitols with methanolic sulfuric or hydrochloric acid at −30 °C leads to their regiospecific conversion to the corresponding methyl glycofuranosides. The reaction exhibits more pronounced stereoselectivity for 1-deoxy-1-nitroalditols with the 2,3-erythro configuration than with the 2,3-threo substrates and cis methyl glycofuranosides are the major products. The observed stereoselectivity indicates the lysis of the protonated aci-nitro form which is a two-step process consisting of nucleophilic addition to the protonated carbon-nitrogen double bond followed by the bimolecular nucleophilic substitution of the nitrogen-containing residue.     

Radical terpolymerization of sulfur dioxide,hexene-1, and methyl acrylate or methyl methacrylate

The radical terpolymerization of sulfur dioxide, hexene-1, and methyl acrylate has been investigated, and from the dilution effects on composition of the terpolymer it would seem reasonable to rule out the possibility of the participation of the charge-transfer complex in the propagation process. We have also carried out terpolymerization of sulfur dioxide, hexene-1, and methyl methacrylate and obtained a terpolymer having the block nature.     

The synthesis of methyl 1-aryl-2-pyrrolecarboxylates

A series of alkyl 1-(aryl)-2-pyrrolecarboxylates were prepared by the condensation of the appropriate aniline with methyl tetrahydro-2,5-dimethoxy-2-furancarboxylate in refluxing acetic acid. It was found that condensation proceeds even in substituents possessing steric bulk are present in the ortho positions of the aniline. Strong electron withdrawing substituents if conjugated to the nitrogen diverts the reaction from product to unidentified tars.     

Excess enthalpies of (methyl propanoate or methyl pentanoate + 1-alkanol) at 298.15 K

The excess molar enthalpies H_m^E of methyl propanoate or methyl pentanoate + 1-butanol, + 1-hexanol, + 1-octanol, and + 1-decanol have been determined experimentally at 298.15 K using a Calvet microcalorimeter. For all these mixtures H_m^E > 0; the values increase with the chain length of the alkanol but decrease as the ester chain lengthens.     

Total synthesis of prostaglandin D1 methyl ester and 9-epi-prostaglandin D1 methyl ester

Synthesis of the title compounds are described via the dithiane enone (VIII); cuprate addition to (VIII) proceeds with asymmetric induction.     

Reactions of 1-halocyclohexenes and methyl substituted 1-halocyclohexenes with potassium t-butoxide

Reactions of 1-halocyclohexenes and 1-halo-4-methylcyclohexenes with potassium t-butoxide (t-BuOK) in dimethyl sulfoxide and tetrahydrofuran have been shown to take place by three competing dehydrohalogenation mechanisms. These are: dehydrohalogenation across the C₁C₆ bond to give a cyclohexyne; dehydrohalogenation across the C₁C₆ bond to give a 1,2-cyclohexadiene: and prototropic rearrangement to the corresponding 3-halocyclohexene, followed by β-elimination to a 1,3-cyclohexadiene. The highly strained cyclohexyne and 1,2-cyclohexadiene intermediates react with t-BuOK to give 1-t-butoxycyclohexene, which is obtained in yields ranging from 5–20% in DMSO to about 60% in THF. Competitive with the substitution reaction is dimerization of 1,2-cyclohexadiene to tricyclo[6.4.0.0^2,7]-dodeca-2,12-diene, and 1,2- and 1,4-cycloaddition of 1,2- and 1,3-cyclohexadiene.     

Nucleophilic addition of phenol derivatives to methyl 1-nitrocyclopropanecarboxylates

Nucleophilic ring opening of methyl 1-nitrocyclopropanecarboxylates by phenol derivatives in the presence of Cs2CO3 is described. The reaction tolerates a variety of substituents on both the aromatic alcohol and the cyclopropane and affords the products in good yields (53-84%) and with complete preservation of the enantiomeric excess at C-4. The methodology was applied in an enantioselective synthesis of the norepinephrine reuptake inhibitor atomoxetine (Strattera).     

Reformatsky reaction of methyl 1-bromocyclobutane- and 1-bromocycloheptanecarboxylates with Schiff bases

Reformatsky reagents derived from methyl 1-bromocyclobutane- and 1-bromocycloheptanecarboxylates reacted with Schiff bases to give 2,3-diaryl-2-azaspiro[3.3]heptane-1-ones and 2,3-diaryl-2-azaspiro-[3.6]decan-1-ones, respectively.     

Synthesis of methyl(1-aminophosphonate)siloxane oligomers

A synthesis of 1-aminophosphonate derivative of methylsiloxane oligomer was developed. A methodology of the introduction of 1-aminophosphonate fragment not only into the stable siloxane structures, but also into hydrolytically unstable alkoxyfunctional organosilicon compounds was suggested.     

Transformations of methyl 2-(2,2-disubstituted-ethenyl)amino-3-dimethylaminopropenoates. The synthesis of methyl 1-heteroaryl-1H-imidazole-4-carboxylates

Transformations of intermediates 4 , prepared from methyl 2-(2,2-disubstituted-ethenyl)amino-3-dimethylaminopropenoates 2 and sterically hindered heteroarylamines 3 , into methyl 1-heteroaryl-1H-imidazole-4-carboxylates 7 are described.     

1-[(乙氧基)甲基]-6-(1-萘甲基)胸腺嘧啶的合成

HEPT是抑制HIV-1逆转录酶的潜在活性化合物。1-[(乙氧基)甲基]-6-(1-萘甲基)胸腺嘧啶是HEPT的类似物,通过增加6位取代基的位阻可提高药效。文献设计并合成了该化合物,并对关键中间体(d)的合成及脱羟基反应作了初步讨论。     

Molecular structures of methyl 4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-5-carboxylate and methyl 4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-3-carboxylate

The structure of methyl 4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-5-carboxylate is determined by X-ray crystallography and further used to elucidate the structure of methyl 4-[(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)methyl]-1-methyl-1H-pyrazol-3-carboxylate, using the data of homo- and heteronuclear 2D NMR correlation spectroscopy.