Guanidine in the synthesis of perfluoroalkylpyrimidines and perfluoroalkyl-s-triazines

Perfluoro-2-methylpent-2-ene and perfluoro-5-azanon-4-ene react with guanidine hydrochloride in the presence of triethylamine to give 2-amino-6-fluoro-4-pentafluoroethyl-5-trifluoromethylpyrimidine and 2-amino-4,6-bis(heptafluoropropyl)-1,3,5-triazine, respectively. The structure of the former product was confirmed by X-ray diffraction analysis.     

1,3-Dipolar cycloaddition of diazomethane and diazocyclopropane to 2-fluoro-3-methylbutadiene and thermal transformations of fluorine-containing vinylpyrazolines and vinylcyclopropanes

Reactions of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15 °C and with diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K₂CO₃ in CH₂Cl₂ at –10 °C selectively involve the double bond at the methyl group to give 3-(1-fluorovinyl)-3-methylpyrazolines. Thermal dediazotization of the latter at 250 °C yields 1-(1-fluorovinyl)-1-methylcyclopropane and -spiropentane 5, which are capable of isomerizing, under more severe conditions (400—600 °C), into 1-fluoro-2-methylcyclopent-1-ene and 5-fluoro-4-methylspiro[2.4]hept-4-ene (7), respectively. Spiropentane derivative 5 partially isomerizes into 1-fluoro-2-methyl-3-methylidenecyclohex-1-ene. In a similar way, thermolysis of 6-(2,3,3-trifluorocyclobut-1-enyl)-4,5-diazaspiro[2.4]hept-4-ene at 400 °C gives a mixture of 1-(spiropentyl)-2,3,3-trifluorocyclobut-1-ene and 2,3,3-trifluoro-1-(2-methylidenecyclobutyl)cyclobut-1-ene. Thermolysis of 1-cyclopropyl-2,3,3-trifluorocyclobut-1-ene at 550—620 °C affords a mixture of 1-(trifluorovinyl)cyclopentene and 2,3-difluorotoluene.     

Regioselective synthesis of 5-trifluoromethyl-1,2,3-triazole nucleoside analogues via TBS-directed 1,3-dipolar cycloaddition reaction

Herein described was a straightforward method for the highly regioselective synthesis of 5-trifluoromethyl-1,2,3-triazole nucleoside analogues, which featured the utilization of tert-butyldimethylsilyl (TBDMS) group as the directing group in the 1,3-dipolar cycloaddition reactions. 4-tert-Butyldimethylsilyl-5-trifluoromethyl-1,2,3-triazole nucleoside analogues were generated as the only cycloaddition products in moderate yields (15-79%) via the treatment of glycosyl azides with 3,3,3-trifluoro-1-tert-butyldimethylsilylpropyne 1 in toluene at 85 °C. Removal of TBS groups in these triazole cycloadducts with tetrabutylammonium fluoride (TBAF) smoothly afforded the various 5-trifluoromethyl-1,5-disubstituted 1,2,3-triazole nucleoside analogues in good yields (40-88%).     

2-Polyfluoroalkylchromones. 9. Synthesis and structures of 5-(2-hydroxyaryl)-7-polyfluoroalkyl-1,4,8-triazabicyclo[5.3.0]dec-4-enes

2-Polyfluoroalkylchromones reacted with diethylenetriamine at 20 °C to form the corresponding 1,4,8-triazabicyclo[5.3.0]dec-4-ene derivatives. The crystal structures of 5-(2-hydroxyphenyl)-7-trifluoromethyl-1,4,8-triazabicyclo[5.3.0]dec-4-ene and 1-(2-aminoethyl)-7-(2-hydroxy-5-methoxyphenyl)-5-(1,1,2,2-tetrafluoroethyl)-2,3-dihydro-1H-1,4-diazepine were established by X-ray diffraction analysis.     

Synthesis of side-chain monofluorinated amphetamines

R- and S-2-Amino-3-fluoro-1-phenylprupane were prepared in approximately 50% yields by the action of HF-pyridine on R- and S-2-benzylaziridine. (±)-2-Amino-3-fluoro-1-(4-chlorophenyl)propane was similarly prepared from (±)-2-(4-chlorobenzyl)aziridine. Structures of products were confirmed by n.m.r. and mass spectroscopy. In contrast, when 2-benzyl-N-tosylaziridine was reacted with HF in pyridine, the C₂ atom of the aziridine ring was the site of fluorination and the N-tosylated derivative of 3-amino-2-fluoro-1-phenylpropane was obtained in excellent yield.     

Reactions of tetrafluoroethylene oligomers. Part 1. Some pyrolytic reactions of the pentamer and hexaher and of the fluorine adducts of the tetramer and pentamer

Pyrolyses of these highly branched fluorocarbons over glass beads caused the preferential thermolyses of CC bonds where there is maximum carbon substitution. Fluorinations of perfluoro-3,4-dimethylhex-3-ene (tetramer) (I) and perfluoro-4-ethyl-3,4-dimethylhex- 2-ehe (pentamer) (II) over cobalt (III) fluoride at 230° and 145° respectively afforded the corresponding saturated fluorocarbons (III) and (IV), though II gave principally the saturated tetramer (III) at 250°. Pyrolysis of III alone at 500—520° gave perfluoro-2-methylbutane (V), whilst pyrolysis of III in the presence of bromine or toluene afforded 2-bromononafluorobutane (VI) and 2H-nonafluorobutane (VII) respectively. Pyrolysis of perfluoro-3-ethyl-3, 4-dimethylhexane (IV) alone gave a mixture of perfluoro-2-methylbutane (V), perfluoro-2-methylbut-1-ene (VIII), perfluoro-3-methylpentane (IX), perfluoro-3,3-dimethylpentane (X), and perfluoro-3,4- dimethylhexane (III). Pyrolysis of IV in the presence of bromine gave (VI) and 3-bromo-3-trifluoromethyl-decafluoropentane (XI): with toluene, pyrolysis gare VlI and 3H-3-trifluoromethyldecafluoropentane (XII). Pyrolysis of II at 500° over glass gave perfluoro-1,2,3-trimethylcyclobutene (XIII) and perfluoro-2,3-dimethylpenta-1,3(E)- and (Z)-diene (XIV) and (XV) respectively. The diene mixture (XIV and XV) was fluorinated with CoF₃ to give perfluoro-2,3-dimethylpentane (XVI) and was cyclised thermally to give the cyclobutene (XIII). Pyrolysis of perfluoro-2- (1′-ethyl-1′-methylpropyl)-3-methylpent-1-ene (XVII) (TFE hexamer major isomer) at 500° gave perfluoro-1-methyl-2-(1′-methylpropyl)cyclobut-1-ene (XVIII) and perfluoro-2-methyl-2-(1′-methylpropyl)buta-1,3-diene (XIX). Fluorination of XVIII over CoF₃ gave perfluoro-1-methyl-2- (1′-methylpropyl)cyclobutane (XX), which on co-pyrolysis with bromine gave VI. XIX on heating gave XVIII. Reaction of XVIII with ammonia in ether gave a mixture of E and Z 1′-trifluoromethyl-2-(1′-trifluoromethyl- pentafluoropropyliden-1′-yl)tetrafluorocyclobutylamine (XXI) which on diazotisation and hydrolysis afforded 2-(2′trifluoromethyl- tetrafluorocyclobut-1-en-1′-yl)-octafluorobutan-2-ol (XXII).     

Reactions of Perfluoro(5-aza-4-nonene) with Hydrazine and Some Its Derivatives

The reaction of perfluoro(5-aza-4-nonene) with hydrazine hydrate in tetrahydrofuran at 0-20°C in the presence of triethylamine yields 2,5-bis(heptafluoropropyl)-1H-1,2,4-triazole; under similar conditions perfluoro(5-aza-4-nonene) reacts with arylhydrazines to form 1-aryl-3,5-bis(heptafluoropropyl)-1,2,4-triazoles.     

Expeditious asymmetric synthesis of a stereoheptad corresponding to the C(19)-C(27)-ansa chain of rifamycins: formal total synthesis of Rifamycin S

In the presence of sulfur dioxide and an acid promoter, (-)-(1E,3Z)-2-methyl-1-((1S)-1-phenylethoxy)penta-1,3-dien-3-yl isobutyrate reacts with (Z)-3-(trimethylsilyloxy)pent-2-ene giving a silyl sulfinate intermediate that undergoes, in the presence of palladium catalyst, a desilylation and retro-ene elimination of SO(2) with formation of (-)-(1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-5-oxo-3-((1S)-1-phenylethoxy)-heptyl isobutyrate as major product. This ethyl ketone undergoes cross-aldol reaction with (2S)-2-methyl-3-[(tert-butyldimethylsilyl)oxy]propanal giving an aldol that is reduced into a stereoheptad corresponding to the C(19)-C(27)-segment of Rifamycins with high diastereoselectivity and enantiomeric excess.     

Preparation of optically pure α-trifluoromethyl-α-amino acids from N-tosyl-2-trifluoromethyl-2-alkyloxycarbonyl aziridine

The preparation of optically pure α-trifluoromethyl-α-amino acids from N-tosyl-2-trifluoromethyl-2-alkyloxycarbonylaziridine is described. Optically pure aziridine was prepared with a 60% yield via three steps from optically pure 2,3-epoxy-1,1,1-trifluoropropane (TFPO). Ring-opening reactions of the aziridine with a variety of nucleophiles and subsequent deprotection of the N-tosyl moieties gave the optically pure β-substituted-α-trifluoromethyl-α-amino acids in moderate to good yields (up to 85%) without racemization at the quaternary stereogenic center of the amino acid.     

Molecular structure of 1-phenyl-2-trifluoromethyl-3-benzoylaziridine

1-Phenyl-2-trifluoromethyl-3-benzoylaziridine has been studied by X-ray structural analysis. Protons of the aziridine cycle are intrans positions. The C(1)-N(1) bond is the shortest of the corresponding bonds in aziridine derivatives, which have been studied by X-ray structural analysis previously.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1975–1977, October, 1995.     

Synthesis of isomerically pure 3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acid derivatives via the reaction of 4-aryl-6-trifluoromethyl-2-pyrones with sodium azide

Treatment of 4-aryl-6-trifluoromethyl-2-pyrones with sodium azide in DMSO afforded the corresponding (Z)-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids in good yields. Similarly, 4-aryl-3-carbethoxy-6-trifluoromethyl-2-pyrones smoothly reacted with sodium azide in acetonitrile to produce (E)-2-ethoxycarbonyl-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids in high yields, whereas their reactions in ethanol, accompanied by a configurational change, gave the thermodynamically more stable (Z)-2-ethoxycarbonyl-3-(5-trifluoromethyl-1,2,3-triazol-4-yl)cinnamic acids.     

Synthesis of (10Z)- and (10E)-19-fluoro-1alpha,25-dihydroxyvitamin D3: compounds to probe vitamin D conformation in receptor complex by 19F-NMR

To study the interaction of vitamin D with its receptor by 19F-NMR, (5Z,10Z)- and (5Z,10E)-19-fluoro-1alpha,25-dihydroxyvitamin D3 were synthesized starting from vitamin D2 via electrophilic fluorination of vitamin D-SO2 adducts as the key step. Regio- and stereoselective electrophilic fluorination at C(19) of vitamin D-SO2 adducts was achieved under the conditions using (PhSO2)2NF and bulky bases. The stereochemistry of the addition and elimination of SO2 of various vitamin D derivatives was studied in detail. SO2 causes Z-E isomerization of the 5,6-double bond of vitamin D and adds to the resulting (5E)-isomer from the sterically less hindered side opposite to the substituent at C(1). Elimination of SO2 from 19-substituted vitamin D-SO2 adducts proceeded exclusively in a suprafacial manner with respect to the diene part under either thermal or reductive conditions. Dye-sensitized photochemical isomerization of 19-fluorovitamin D derivatives was studied in detail. The rapid isomerization at the 5,6-double bond was followed by the slow isomerization at the 10,19-double bond to yield the (5E,10Z)-isomer (by nomenclature of the 1-OH derivatives) as the major product. (10Z)- and (10E)-19-Fluorovitamin Ds were also interconverted thermally probably via the corresponding previtamin D by 1,7-sigmatropic isomerization.     

2-Polyfluoroalkylchromones. 8. 2-Trifluoromethyl- and 6-nitro-2-trifluoromethylchromones in reactions with amines

The reactions of 6-nitro-2-trifluoromethylchromone with benzylamine, ethanolamine, and aniline afforded 3-benzyl(2-hydroxyethyl,phenyl)amino-4,4,4-trifluoro-1-(2-hydroxy-5-nitrophenyl)but-2-en-1-ones, respectively, whereas the reactions with ethylenediamine and diethylenetriamine gave rise to 5-(2-hydroxy-5-nitrophenyl)-7-trifluoromethyl-2,3-dihydro-1H-1,4-diazepine and 5-(2-hydroxy-5-nitrophenyl)-7-trifluoromethyl-1,4,8-triazabicyclo[5.3.0]dec-4-ene, respectively. Morpholine added at the double bond of 2-trifluoromethyl- and 6-nitro-2-trifluoromethylchromones to form 2-morpholino-2-trifluoromethylchroman-4-one and its 6-nitro-substituted analog, respectively, whereas piperidine reacted only with 2-trifluoromethylchromone to yield 2-piperidino-2-trifluoromethylchroman-4-one.     

Reaction of perfluoro-2-methylpent-2-ene with ethylenediamine and hexamethylenediamine

Reaction of perfluoro-2-methylpent-2-ene with ethylenediamine and hexamethylenediamine results in 9-fluoro-5,9-bis(pentafluoroethyl)-6,8,8-tris(trifluoromethyl)-1,4-diazabicyclo[5.2.0]nona-4,6-diene, whose structure was confirmed by X-ray analysis, and 11-pentafluoroethyl-10-trifluoromethyl-1,8-diazabicyclo[7.2.0]undeca-8,10-diene, respectively. The reaction pathways are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1578–1582, August, 1999.     

A novel reaction of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) to form 2-fluoro-2-trifluoromethyl-4-alkenamide

Treatment of allylic alcohols with hexafluoropropene-diethylamine adduct (PPDA) afforded N,N-diethyl-2-fluoro-2-trifluoromethyl-4-alkenamides which were formed by the Claisen rearrangement of intermediary 2-alkenyl-1-diethylamino-2,3,3,3-tetrafluoro-1-propenyl ethers. Although (E)-allylic alcohols gave two diastereomeric products in about 1:1 ratio, (Z)-allylic alcohols gave the corresponding product as a single diastereomer.     

Heteroleptic cyclometalated iridium(III) complexes displaying blue phosphorescence in solution and solid state at room temperature

A series of heteroleptic Ir(III) metal complexes 1-3 bearing two N-phenyl-substituted pyrazoles and one 2-pyridyl pyrazole (or triazole) ligands were synthesized and characterized to attain highly efficient, room-temperature blue phosphorescence. The N-phenylpyrazole ligands, dfpzH = 1-(2,4-difluorophenyl)pyrazole, fpzH = 1-(4-fluorophenyl)pyrazole, dfmpzH = 1-(2,4-difluorophenyl)-3,5-dimethylpyrazole, and fmpzH = 1-(4-fluorophenyl)-3,5-dimethylpyrazole, show a similar reaction pattern with respect to the typical cyclometalated (C(wedge)N) chelate, which utilizes its ortho-substituted phenyl segment to link with the central Ir(III) atom, while the second 2-pyridylpyrazole (or triazole) ligand, namely, fppzH = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole, fptzH = 3-(trifluoromethyl)-5-(2-pyridyl)triazole, and hptzH = 3-(heptafluoropropyl)-5-(2-pyridyl)triazole, undergoes typical anionic (N--N) chelation to complete the octahedral framework. X-ray structural analyses on complexes [(dfpz)(2)Ir(fppz)] (1a) and [(fmpz)(2)Ir(hptz)] (3d) were established to confirm their molecular structures. Increases of the pipi energy gaps of the Ir(III) metal complexes were systematically achieved with two tuning strategies. One involves the substitution for one or two fluorine atoms at the N-phenyl segment or the introduction of two electron-releasing methyl substituents at the pyrazole segment of the H(C--N) ligands. Alternatively, we have applied the more electron-accepting triazolate in place of the pyrazolate segment for the third (N--N)H ligand. Our results, on the basis of steady-state, relaxation dynamics, and theoretical approaches, lead to a conclusion that, for complexes 1-3, the weakening of iridium metal-ligand bonding strength in the T(1) state plays a crucial role for the fast radiationless deactivation. For the case of [(fmpz)(2)Ir(hptz)] (3d), a thermal deactivation barrier of 4.8 kcal/mol was further deduced via temperature-dependent studies. The results provide a theoretical basis for future design and synthesis of the corresponding analogues suited to blue phosphorescent emitters.     

Synthesis and Crystal Structure of 2-(4-Fluoro-2-(4-fluorophenoxy) phenyl)-1-(1H-1,2,4-triazol-l-ylmethyl)-3-methoxy-isopropy Alcohol

The title compound 2-(4-fluoro-2-(4-fluorophenoxy)phenyl)-1-(1H-1,2,4-triazol-z 1-ylmethyl)-3-methoxy-isopropy alcohol has been synthesized by the treatment of 1-[2-(4-fluoro-2-(4-fluorophenoxy)phenyl)-2,3-epoxypropyl]-1H-1,2,4-tdazole with sodium methoxide. It be-longs to orthorhombic, space group P212121, with a=9.7229(19), b=11.516(2), c=16.047(3) A, C18H17F2N3O3, Mr-361.35, V=1796.7(6) A3, Z=4, Dc=1.3359 g/cm3, F(000)=752,μ=0.106 mm-1, the final R=0.0329 and wR=0.0803 for 1821 unique reflections. The dihedral angles made by the triazole ring with two benzene rings are 43.56(3) and 54.78(2)°, respectively. The intermolecular hydrogen bond in the crystal lattice plays an important role in stabilizing the structure.     

Synthesis and Crystal Structure of 2-（4-Fluoro-2-（4-fluorophenoxy）phenyl）-1-（1H- 1,2,4-triazol-1-ylmethyl）-3-methoxy-isopropy Alcohol

The title compound 2-（4-fluoro-2-（4-fluorophenoxy）phenyl）-1-（1H-1,2,4-triazol- 1-ylmethyl）-3-methoxy-isopropy alcohol has been synthesized by the treatment of 1-[2-（4-fluoro- 2-（4-fluorophenoxy）phenyl）-2,3-epoxypropyl]-1H-1,2,4-triazole with sodium methoxide. It belongs to orthorhombic, space group P212121, with a = 9.7229（19）, b = 11.516（2）, c = 16.047（3）A, C18H17F2 N3O3, Mr = 361.35, V = 1796.7（6）A^3, Z = 4, Dc = 1.3359 g/cm^3, F（000） = 752, p = 0.106 mm^-1, the final R = 0.0329 and wR = 0.0803 for 1821 unique reflections. The dihedral angles made by the triazole ring with two benzene rings are 43.56（3） and 54.78（2）°, respectively. The intermolecular hydrogen bond in the crystal lattice plays an important role in stabilizing the structure.     

Stereoselective synthesis of (Z)-2-fluoro-1-alkenyl(phenyl)iodonium tetrafluoroborates

[reaction: see text] (Z)-2-Fluoro-1-alkenyl(phenyl)iodonium salts were stereoselectively prepared by the reaction of alkynyl(phenyl)iodonium salts with aqueous HF in good yields. The method is applicable to the synthesis of fluoroalkenyliodonium salts having functional groups such as ketone, ester, and chloride. (Z)-2-Fluoro-1-alkene, (Z)-2-fluoro-2-alkenoate, and (Z)-beta-fluoroenyne could be stereoselectively prepared from the fluoroalkenyliodonium salt.     

Modification of biologically active amides and amines with fluorine-containing heterocycles 2*. N-(2-Thienyl)imines on the base of methyl trifluoropyruvate in cyclocondensation with 1,3-N,N-binucleophiles

An approach to the modification of the biologically active compounds, substituted 2-aminothiophenes, with fluorine-containing five-membered heterocycles is proposed. The reaction of 2-aminothiophenes with methyl trifluoropyruvate yields the corresponding N-(2-thienyl)imines, their subsequent cyclocondensation with 1,3-N,N-binucleophiles (2-aminothiazoline and benzamidines) furnished 5-oxo-6-trifluoromethyl-2,3,5,6-tetrahydroimidazothiazoles and 5-oxo-2-phenyl-4-trifluoromethyl-4,5-dihydro-1H-imidazoles.