Presence Of Hexafluorophosphoric Acid Research Articles

A facile preparation, spectroscopic and chemical properties, crystal structures, and electrochemical behavior of monocarbenium ion compounds stabilized by 3-guaiazulenyl and dihydroxyphenyl (or hydroxymethoxyphenyl) groups

Reaction of guaiazulene ( 8) with 2,3-dihydroxybenzaldehyde ( 9) in methanol in the presence of hexafluorophosphoric acid (i.e., 65% aqueous solution) at 25 °C for 2 h gives (3-guaiazulenyl)(2,3-dihydroxyphenyl)methylium hexafluorophosphate ( 13) in 86% yield. Similarly, reaction of 8 with 2-hydroxy-3-methoxybenzaldehyde ( 10) [or 3,4-dihydroxybenzaldehyde ( 11) or 4-hydroxy-3-methoxybenzaldehyde ( 12)] under the same reaction conditions as for 9 affords the corresponding monocarbenium ion compound 14 (63% yield) [or 15 (43% yield) or 16 (77% yield)], respectively, each product of which is stabilized by 3-guaiazulenyl and dihydroxyphenyl (or hydroxymethoxyphenyl) groups. A facile preparation and crystal structures as well as spectroscopic, chemical, and electrochemical properties of 13– 16, possessing two interesting resonance structures, respectively, i.e., a protonated o- (or p-) benzoquinonemethide form and a 3-guaiazulenylium ion form, in a solution of acetonitrile and further, in a single crystal, are reported.

Preparation, Structures, and Properties of New Monocarbenium Ion Compounds Stabilized by a 3-Guaiazulenyl Group and an Azobenzene Unit: Comparative Studies on Three Delocalized π-Electron Systems

Abstract Reaction of guaiazulene (=7-isopropyl-1,4-dimethylazulene) with 4′-hydroxyazobenzene-4-carbaldehyde in methanol in the presence of hexafluorophosphoric acid at 25 °C for 2 h gives as high as 94% yield of a new monocarbenium ion compound (3-guaiazulenyl)[4-(4-hydroxyphenylazo)phenyl]methylium hexafluorophosphate. Similarly, reactions of guaiazulene with 4′-methoxyazobenzene-4-carbaldehyde and 4′-(dimethylamino)azobenzene-4-carbaldehyde under the same reaction conditions as the above afford the corresponding new (3-guaiazulenyl)[4-(4-methoxyphenylazo)phenyl]methylium and {4-[4-(dimethylamino)phenylazo]phenyl}(3-guaiazulenyl)methylium hexafluorophosphates in 97 and 95% yields. Along with an efficient preparation of the target monocarbenium ion compounds, comparative studies on spectroscopic, chemical, and electrochemical properties of the unique products, indicating different delocalized π-electron systems, are reported. Moreover, crystal structure of {4-[4-(dimethylamino)phenylazo]phenyl}(3-guaiazulenyl)methylium tetrafluoroborate with an equiv of HBF4 molecule is documented.

A Facile Preparation of (4-Aminophenyl)(3-guaiazulenyl)methylium Hexafluorophosphate: Comparative Studies on Spectroscopic, Chemical, and Electrochemical Properties of Monocarbenium Ion and p-Benzoquinodimethane Monoiminium Ion Compounds

Abstract Reaction of guaiazulene with 4-aminobenzaldehyde in CH3OH in the presence of hexafluorophosphoric acid at 25 °C for 2 h gives the title compound, with an equiv of HPF6, in 56% yield. Interestingly, a solution of the obtained new monocarbenium ion compound, forming a protonated amino group (4-H3N+PF6−), in CH3CN is allowed to stand at room temperature for 48 h, gradually converting to a new 4-(3-guaiazulenyl)methylene-2,5-cyclohexadiene-1-iminium hexafluorophosphate, completely. Furthermore, reductions of the above two products with NaBH4 in a mixed solvent of EtOH and CH3CN afford 4-amino-1-(3-guaiazulenylmethyl)benzene, selectively. Comparative studies on spectroscopic, chemical, and electrochemical properties of the monocarbenium ion compound with those of the 4-methylene-2,5-cyclohexadiene-1-iminium ion compound, are reported.

メタノール中六フッ化リン酸存在下グアイアズレンとアルデヒド基を有するアゾ化合物との反応：3-グアイアズレニル基により安定化されたモノカルボカチオン化合物の分子構造とスペクトル、化学的および電気化学的特性

メタノール中六フッ化リン酸存在下グアイアズレンとアルデヒド基を有するアゾ化合物との反応：3-グアイアズレニル基により安定化されたモノカルボカチオン化合物の分子構造とスペクトル、化学的および電気化学的特性

An efficient preparation and spectroscopic and electrochemical properties of quinodimethane derivatives with four 3-(methoxycarbonyl)azulen-1-yl groups

Reaction of methyl 1-azulenecarboxylate ( 8) with terephthalaldehyde ( 9) in acetic acid in the presence of hydrochloric acid at 25 °C for 2 h gives 1,4-bis[bis(3-methoxycarbonyl-1-azulenyl)methyl]benzene ( 12), in 93% yield, which upon oxidation with 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ) in dichloromethane in the presence of hexafluorophosphoric acid at 25 °C for 1 h affords the dicarbenium-ion compound 15 in 94% yield. Furthermore, reduction of 15 with zinc powder in a mixed solvent of acetonitrile and chloroform at 25 °C for 1 h yields the target quinodimethane 18 in 90% yield. Similarly, as in the case of 18, the quinoid compounds 19 and 20 can be derived from the dicarbenium-ion compounds 16 and 17, quantitatively. A facile preparation as well as spectroscopic and electrochemical properties of 15– 20 is reported.

An efficient preparation, crystal structures, and properties of monocarbenium-ion compounds stabilized by 3-guaiazulenyl and anisyl groups

Reaction of guaiazulene ( 1) with 2-methoxybenzaldehyde ( 2) in methanol in the presence of hexafluorophosphoric acid at 25 °C for 2 h gives (3-guaiazulenyl)(2-methoxyphenyl)methylium hexafluorophosphate ( 5a) in 93% yield. Similarly, reaction of 1 with 3-methoxybenzaldehyde ( 3) or 4-methoxybenzaldehyde ( 4) under the same reaction conditions as for 2 affords (3-guaiazulenyl)(3-methoxyphenyl)methylium hexafluorophosphate ( 6) (91% yield) or (3-guaiazulenyl)(4-methoxyphenyl)methylium hexafluorophosphate ( 7) (97% yield). The crystal structures as well as the spectroscopic, electrochemical, and chemical properties of these monocarbenium-ion compounds, possessing interesting resonance forms, stabilized by the 3-guaiazulenyl and anisyl (i.e., 2-, 3-, or 4-methoxyphenyl) groups are reported.

Reactions of azulene and guaiazulene with all- trans-retinal and trans-cinnamaldehyde: comparative studies on spectroscopic, chemical, and electrochemical properties of monocarbenium-ions stabilized by expanded π-electron systems with an azulenyl or 3-guaiazulenyl group

Reaction of azulene ( 1) with all- trans-retinal in diethyl ether in the presence of hexafluorophosphoric acid at −10 °C for 1 h in a dark room gives the corresponding monocarbenium-ion compound, (2 E,4 E,6 E,8 E)-1-azulenyl-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate ( 3), in 74% isolated yield. The spectroscopic, chemical, and electrochemical properties of 3 compared with those of the previously-documented (2 E,4 E,6 E,8 E)-1-(3-guaiazulenyl)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate ( 4) are reported. Along with the above delocalized monocarbenium-ion compounds 3 and 4, stabilized by the expanded π-electron systems possessing an azulenyl (or 3-guaiazulenyl) group, an efficient preparation as well as the spectroscopic, chemical, and electrochemical properties of (2 E)-1-azulenyl-3-phenyl-2-propen-1-ylium and (2 E)-1-(3-guaiazulenyl)-3-phenyl-2-propen-1-ylium hexafluorophosphates ( 5 and 6) (90 and 96% isolated yields), having a similar partial structure [i.e., the (2 E)-1-azulenyl-2-propen-1-ylium-ion or (2 E)-1-(3-guaiazulenyl)-2-propen-1-ylium-ion part] to those of 3 and 4, is documented. Moreover, the crystal structure of 6, whose carbenium-ion framework is planar, is shown.

Reaction of guaiazulene with o-formylbenzoic acid in diethyl ether (or methanol) in the presence of hexafluorophosphoric acid: comparative studies on 1H and 13C NMR spectral properties of 3-guaiazulenylmethylium- and 3-guaiazulenium-ion structures

Reaction of guaiazulene ( 1) with o-formylbenzoic acid ( 2) in diethyl ether in the presence of hexafluorophosphoric acid at 25 °C for 90 min gives the corresponding monocarbenium-ion compound, [2-(carboxy)phenyl](3-guaiazulenyl)methylium hexafluorophosphate ( 3), quantitatively, which upon treatment with aq NaHCO 3 leads to 3-(3-guaiazulenyl)-2-benzofuran-1(3 H)-one ( 5) in 96% isolated yield. Similarly, reaction of 1 with 2 in methanol under the same conditions as the above reaction affords two kinds of inseparable monocarbenium-ion compounds, 3 and (3-guaiazulenyl)[2-(methoxycarbonyl)phenyl]methylium hexafluorophosphate ( 4) with an equilibrium between them, which upon reaction with a solution of NaBH 4 in ethanol at 25 °C for 30 min leads to 5 in 46% isolated yield and (3-guaiazulenyl)[2-(methoxycarbonyl)phenyl]methane ( 6) in 37% isolated yield. Along with the 1H and 13C NMR spectral properties of a solution of 5 in trifluoroacetic acid- d 1 at 25 °C, whose molecular structure is converted to a ca. 1:1 equilibrium mixture of 7 possessing a partial structure of the 3-guaiazulenylmethylium-ion and 8 possessing a partial structure of the 3-guaiazulenium-ion, comparative studies on the 1H and 13C NMR spectral properties of 7 and 8 with those of the monocarbenium-ion compound, (3-guaiazulenyl)[4-(methoxycarbonyl)phenyl]methylium hexafluorophosphate ( A), 5, and 6 are reported. From these NMR studies, it can be inferred that the positive charge of the 3-guaiazulenylmethylium-ion part of 7 apparently is transferred to the seven-membered ring, generating a resonance form of the 3-guaiazulenylium-ion structure η′, and the same result can be inferred for the previously documented monocarbenium-ion compounds A– I. Moreover, referring to a comparative study on the C–C bond lengths of A observed by the X-ray crystallographic analysis with those of the optimized (3-guaiazulenyl)[4-(methoxycarbonyl)phenyl]methylium-ion structure for A calculated by a WinMOPAC (Ver. 3.0) program using PM3, AM1, or MNDOD as a semiempirical Hamiltonian, the optimized [2-(carboxy)phenyl](3-guaiazulenyl)methylium-ion structure for 3 calculated using PM3 is described.

Reactions of guaiazulene with thiophene-2,5-dicarbaldehyde and furan-2,5-dicarbaldehyde in methanol in the presence of hexafluorophosphoric acid: a facile preparation and properties of delocalized dicarbenium-ion compounds stabilized by two 3-guaiazulenyl groups and a thiophene (or furan) ring

Reaction of guaiazulene ( 1) with thiophene-2,5-dicarbaldehyde ( 2) in methanol in the presence of hexafluorophosphoric acid at 25 °C for 3 h gives as high as 90% isolated yield of the delocalized dicarbenium-ion compound, 2,5-thienylenebis(3-guaiazulenylmethylium) bis(hexafluorophosphate) ( 3). Similarly, reaction of 1 with furan-2,5-dicarbaldehyde ( 4) under the same conditions as the above reaction affords the corresponding dicarbenium-ion compound, 2,5-furylenebis(3-guaiazulenylmethylium) bis(hexafluorophosphate) ( 5), in 84% isolated yield. Along with a facile preparation and the spectroscopic and electrochemical properties of 3 and 5, comparative studies on the 1H and 13C NMR spectral and chemical properties of 3 and 5 with those of the delocalized mono- and dicarbenium-ion compounds [i.e., (3-guaiazulenyl)(2-thienyl)methylium hexafluorophosphate ( 7), (2-furyl)(3-guaiazulenyl)methylium hexafluorophosphate ( 9), α,α′-bis(3-guaiazulenylmethylium) bis(tetrafluoroborate) ( 10), 1,2-phenylenebis(3-guaiazulenylmethylium) bis(hexafluorophosphate) ( 11), and 1,4-phenylenebis(3-guaiazulenylmethylium) bis(tetrafluoroborate) ( 12)] are reported. Moreover, referring to the results of the X-ray crystallographic analyses of 7, 9, 11, and 12, the optimized 2,5-thienylenebis(3-guaiazulenylmethylium)- and 2,5-furylenebis(3-guaiazulenylmethylium)-ion structures for 3 and 5, calculated by a WinMOPAC (version 3.0) program using PM3 as a semiempirical Hamiltonian, are described.

Reactions of guaiazulene with 2-furaldehyde, thiophene-2-carbaldehyde and pyrrole-2-carbaldehyde in methanol in the presence of hexafluorophosphoric acid: comparative studies on molecular structures and spectroscopic, chemical and electrochemical properties of monocarbocations stabilized by 3-guaiazulenyl and 2-furyl (or 2-thienyl or 2-pyrrolyl) groups

Reactions of guaiazulene ( 1 ) with heteroaromatic-carbaldehydes [i.e., 2-furaldehyde ( 2 ), thiophene-2-carbaldehyde ( 3 ) and pyrrole-2-carbaldehyde ( 4 )] in methanol in the presence of hexafluorophosphoric acid at 25 °C for 30 min under aerobic conditions give (2-furyl)(3-guaiazulenyl)methylium hexafluorophosphate ( 5 ), (3-guaiazulenyl)(2-thienyl)methylium hexafluorophosphate ( 6 ) and (3-guaiazulenyl)(2-pyrrolyl)methylium hexafluorophosphate ( 7 ), respectively, in 93, 98 and 85% yields. Comparative studies on the molecular structures as well as the spectroscopic, chemical and electrochemical properties of the methylium hexafluorophosphates 5– 7 stabilized by 3-guaiazulenyl and 2-furyl (or 2-thienyl or 2-pyrrolyl) groups are reported.

Reactions of guaiazulene with methyl terephthalaldehydate and 2-hydroxy- and 4-hydroxybenzaldehydes in methanol in the presence of hexafluorophosphoric acid: comparative studies on molecular structures and spectroscopic, chemical and electrochemical properties of monocarbocations stabilized by 3-guaiazulenyl and phenyl groups

Reaction of guaiazulene ( 1 ) with methyl terephthalaldehydate ( 2 ) in methanol in the presence of hexafluorophosphoric acid at 25 °C for 2 h under aerobic conditions gives (3-guaiazulenyl)[4-(methoxycarbonyl)phenyl]methylium hexafluorophosphate ( 5 ) in 94% yield. Similarly, reactions of 1 with 2-hydroxybenzaldehyde ( 3 ) and 4-hydroxybenzaldehyde ( 4 ) under the same reaction conditions as 2 give (3-guaiazulenyl)(2-hydroxyphenyl)methylium hexafluorophosphate ( 6 ) and (3-guaiazulenyl)(4-hydroxyphenyl)methylium hexafluorophosphate ( 7 ) in 89 and 97% yields, respectively. Comparative studies on the molecular structures as well as the spectroscopic, chemical and electrochemical properties of the monocarbocation compounds 5– 7 stabilized by 3-guaiazulenyl and 4-(methoxycarbonyl)phenyl (or 2-hydroxy- or 4-hydroxyphenyl) groups are reported.

The Facile Preparation, Crystal Structure, and Chemical and Electrochemical Properties of 9‐Anthryl‐3‐guaiazulenylmethylium Hexafluorophosphate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Facile Preparation, Crystal Structure, and Chemical and Electrochemical Properties of 9-Anthryl-3-guaiazulenylmethylium Hexafluorophosphate

Abstract Reaction of guaiazulene (1) with anthracene-9-carbaldehyde in methanol in the presence of hexafluorophosphoric acid at 25 °C for 30 min gave the title compound 2 in 88% yield.

A Facile Preparation and Properties of (2E,4E,6E,8E)-1-(3-Guaiazulenyl)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium Hexafluorophosphate

Abstract Reactions of guaiazulene (1) with all-trans- and 13-cis-retinals (2a and 2b) in methanol in the presence of hexafluorophosphoric acid at −10 °C for 1 h afforded the title monocarbocation compound 3 in 87–91% yield, respectively.

The crystal structure and characteristic chemical property of 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate

Reaction of guaiazulene ( 1 ) with a 0.5 molar amount of phthalaldehyde in a mixed solvent of acetonitrile and diethyl ether in the presence of hexafluorophosphoric acid at 25°C under aerobic conditions rapidly gives the title dicarbocation compound, 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluoro-phosphate ( 2 ) in 98% yield. Reduction of 2 with a large excess of NaBH 4 in a mixed solvent of acetonitrile and ethanol at 25°C quantitatively affords a unique intra-molecular cycloaddition compound 9 via the intermediate 8 . The crystal structure and characteristic chemical property of 2 are reported.

An efficient preparation, the structure and the properties of 1-isopropyl-4-(3-guaiazulenylmethylium)benzene hexafluorophosphate and tetrafluoroborate

Reactions of guaiazulene ( 1 ) with 4-isopropylbenzaldehyde in acetic acid in the presence of hexafluorophosphoric acid (and tetrafluoroboronic acid) at 25°C for 2 h under aerobic conditions quantitatively give the new title monocarbocation compounds, 1-isopropyl-4-(3-guaiazulenylmethylium)benzene hexafluorophosphate ( 4 ) and the tetrafluoroborate ( 5 ), which upon reaction with sodium methoxide dissolved in methanol in acetonitrile at 0°C for 20 min, respectively, afford as high as 92% isolated yield of 1-isopropyl-4-(3-guaiazulenylmethoxymethyl)benzene ( 8 ). The crystal structure of 5 , as the first example of carbocations stabilized by azulenyl groups, and the characteristic and chemical properties of 4 and 5 are reported.

An efficient preparation and the properties of 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate

Reaction of guaiazulene ( 1 ) with a 0.5 molar amount of phthalaldehyde in acetic acid in the presence of hexafluorophosphoric acid at 25°C for 2 h under aerobic conditions quantitatively gives the title new dicarbocation compound, 1,2-bis(3-guaiazulenylmethylium)benzene bishexafluorophosphate ( 3 ), which upon reduction with zinc powder in acetonitrile at 0°C under aerobic conditions rapidly affords a unique rearrangement product, 6,11-dimethyl-12-(3-guaiazulenyl)-9-isopropylnaphtho[2,3- a]azulene ( 5 ), as a major product.