Oxetane vs. cyclobutane formation in the photocycloaddition of enones to olefins. The photoaddition of 6-fluoro-4,4-dimethyl-2-cyclohexenone to 2,3-dimethyl-2-butene. Preliminary communication

n-π^* Excitation of 6-fluoro-4,4-dimethyl-2-cyclohexenone in the presence of 2,3-dimethyl-2-butene leads selectively to the formation of the corresponding oxetane. The factors which influence the oxetane vs. cyclobutane formation ratio in photoadditions of cyclic enones to olefins are discussed.     

二芳杂环基乙烯的合成及其光致变色反应研究

本文报道了2,3-双 (1,2-二甲基-3-吲哚基)-2-丁烯 (DF1),2,3-双 (1,4-二苯基-2-甲基-3-吡咯基)-2-丁烯 (DF2), 2,3-双(1-对甲苯基-4-苯基-2-甲基-3-吡咯基)-2-丁烯 (DF3), 2,3-双(1-对溴苯基-4-苯基-2-甲基-3-吡咯基)-2-丁烯 (DF4) 和2,3-双 (1-对甲氧苯基-5-苯基-2-甲基-3-吡咯基)-2-丁烯 (DF5) 的合成,以及它们的光致变色行为的研究。特别是DF1和DF5的光呈色和光消色过程进行了较为细致的研究。     

A comparison of hydrogen bonding solvent effects on the singlet oxygen reactions of allyl and vinyl sulfides, sulfoxides, and sulfones

The singlet oxygen (¹Δ_g) photooxidations of 2-methyl-3-phenylthio-2-butene (1a), 1-[(4-nitrophenyl)thio]-2,3-dimethyl-2-butene (2c), 2-methyl-3-phenylsulfinyl-2-butene (3), 2-methyl-3-phenylsulfonyl-2-butene (6), and 1-[(4-nitrophenyl)sulfonyl]-2,3-dimethyl-2-butene (7c) were conducted in the following deuterated solvents: acetonitrile, benzene, chloroform, methanol, or methanol/water mixture. In each case the ene allylic hydroperoxide products and/or the [2+2] cycloaddition products were quantified and inspected for possible hydrogen bonding induced differences in product selectivity and regiochemistry. After comparison to literature values for related substrates, the results indicate that only photooxidations of vinyl sulfides are susceptible to hydrogen bonding solvent effects.     

Photocycloaddition of 2-Cyanocycloalk-2-Enones to 2, 3-Dimethylbut-2-Ene

Irradiation of 5,5-dimethyl-6-oxocyclohex- l-ene- l-carbonitrile ( 1 ) in the presence of 2,3-dimethylbut-2-ene afforded 3,3,4,4,7,7-hexamethyl-3,4,4a,5,6,7-hexahydroindeno[1,7-c,d]-],2-oxazole (3) in nearly quantitative yield. In contrast, 4,4-dimethyl-5-oxo-cyclopent-l-ene-l-carbonitrile ( 2 ) under the same conditions reacted not to a tricyclic isoxazole but to a 2:1 mixture of 3,3,6,6,7,7-hexamethyl-2-oxo-bicyclo[3.2.0]heptane-l-carbonitrile ( 4 ) and trans-3,3-dimethyl-2-oxo-5-(2,3-dimethylbut-3-en-2-yl)cyclopentane-l-carbonitrile ( 5 ), respectively.     

Rate constants for the reactions of OH radicals with alkyl substituted olefins

Relative rate constants for the reactions of hydroxyl radicals with a series of alkyl substituted olefins were measured by competitive reactions between pairs of olefins at 298 ± 2 K and 1 atmospheric pressure. Hydroxyl radicals were produced by the photolysis of H₂O₂ with 254-nm irradiation. The obtained rate constants were (× 10^?11 cm³ molecule^?1 s^?1): 2.53 ± 0.06, propylene; 5.49 ± 0.17, cis-2-butene; 5.47 ± 0.1, isobutene; 6.46 ± 0.13, 2-methyl-1-butene; 6.37 ± 0.16, cis-2-pentene; 6.23 ± 0.1, 2-methyl-1-pentene; 8.76 ± 0.14, 2-methyl-2-pentene; 6.24 ± 0.08, trans-4-methyl-2-pentene; 10.3 ± 0.1, 2,3-dimethyl-2-butene; 9.94 ± 0.1, 2,3-dimethyl-2-pentene; 5.59 ± 0.07, trans-4,4-dimethyl-2-pentene. A trend in alkyl substituent effect on the rate constant was found, which is useful to predict k_OH on the basis of the number of alkyl substituents on the double bond.     

Five-membered 2,3-dioxo heterocycles: LXIII. Cascade recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with cyclic enamines. Crystalline and molecular structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone

Isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates reacted with N-substituted 3-amino-5,5-dimethylcyclohex-2-en-1-ones to give the corresponding 1′-substituted (Z)-6′,6′-dimethyl-3-[phenyl(arylamino)methylidene]-6′,7′-dihydro-3H-spiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraones. The structure of 1′-benzyl-6′,6′-dimethyl-3-[(Z)-phenyl(phenylamino)methylidene]-6′,7′-dihydro-3Hspiro[furan-2,3′-indole]-2′,4,4′,5(1′H,5′H)-tetraone was proved by X-ray analysis.     

Solvent dependence of singlet oxygen / substrate interactions in ene-reactions, (4+2)- and (2+2)-cycloaddition reactions

Product formation of singlet oxygen reactions with simple olefins occurring as ene-reactions, (4+2)- and (2+2)-cycloaddition reactions is independent on solvent polarity. Thus, 2,3-dimethyl-2-butene (1) and 2-methy]-2-butene (3), 1,3-cyclohexadiene (6), and benzvalene (8) yield allylic hydroperoxides (2) and(4) (54%) + (5) (46%), endoperoxide (7), and dioxetane (9), respectively. The rates of the ene-reactions and (4+2)-cycloaddition reactions are only slightly dependent, those of the (2+2)-cycloaddition reaction, however,are clearly dependent on solvent polarity. “Physical” quenching of singlet oxygen by the olefins is negligible, but substantial by the sensitizer tetraphenylporphin (TPP) in chlorinated solvents.     

Aryl cations from aromatic halides. Photogeneration and reactivity of 4-hydroxy(methoxy)phenyl cation

The photochemistry of 4-chlorophenol (1) and 4-chloroanisole (2) has been examined in a range of solvents and found to lead mainly to reductive dehalogenation, through a homolytic path in cyclohexane and a heterolytic path in alcohols. Heterolysis of 1 and 2 in methanol and 2,2,2-trifluoroethanol offers a convenient access to triplet 4-hydroxy- and 4-methoxyphenyl cations. These add to pi nucleophiles, viz., 2,3-dimethyl-2-butene, cyclohexene, and benzene, giving the arylated products in medium to good yields. Wagner-Meerwein hydride and alkyl migration are evidence for the cationic mechanism of the addition to alkenes. Arylation (with no rearrangement) was obtained to some extent also in nonprotic polar solvents such as MeCN and ethyl acetate, reasonably via an exciplex and with efficiency proportional to the nucleophilicity of the trap (2,3-dimethyl-2-butene > cyclohexene > benzene).     

Reactions of 1-aryl- and 2,3-diaryl- 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetra- hydroindazoles with N-ethyl- and N-phenyl-substituted maleimides

[3+2] Cyclocondensation reactions of a series of 1,3- and 2,3-disubstituted 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles with N-ethyl- and N-phenyl-substituted maleimides have been used to obtain the corresponding 6,6-dimethyl-4,4',6'-trioxo-4,5,6,7-3',3'a,4',5',6',6'a-decahydrospiro-[indazole-5,3'-pyrrolo[3,4-c]pyrazoles]. On boiling these compounds in toluene nitrogen is split off and they are converted into 6',6'-dimethyl-2,4,4'-trioxo-4',5',6',7'-tetrahydro-1'H-spiro[3-azabicyclo-(3.1.0)hexane-6,5'-indazoles].     

Photochemical and thermal transformations of azomethine imines

The thermal and photochemical fragmentations of a few bisazoalkenes have been investigated. 2-Phenyl-4,5-disubstituted-1, 2,3-triazoles were obtained both in the thermolysis and photolysis of 1, 2-bisphenylazo-(4, 4′-dichloro) stilbene, 1, 2-bisphenylazo(4, 4′-dimethoxy)stilbene, 1, 2-bisphenylazocyclohexene and o-(phenylazo) phenyldiazocyanide. Both 2, 3-bisphenylazo-2-butene and 1, 2-bisphenylazoethylene failed to undergo either photolysis or thermolysis in the expected manner. However, 2, 3-bisphenylazo-2-butene underwent an acid-catalysed valence isomerisation to anhydro 1-phenylimino-2-phenyl-4, 5-dimethyl-1, 2, 3-trizolium hydroxide, which on photolysis gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. The same iminotriazolium intermediate gave a cycloadduct, 2, 6-diphenyl-3, 3a-dimethyl-4, 5-dicarbomethoxypyrazolino [2.3.c][1.2.3] triazole, on treatment with dimethyl acetylenedicarboxylate, whereas treatment with carbon disulphide gave 2-phenyl-4, 5-dimethyl-1, 2, 3-triazole. Both photolysis and thermolysis of C-biphenylene-N^α(4-chlorophenyl)-N^β-cyanoazomethine imine gave 9-fluorenone-N- (4-chlorophenyl) anil. Photolysis of 1, 2-bisphenylazoacenaphthylene in methanol gave acenaphthenequinone monophenylhydrazone.     

Ungewöhnliche reaktion eines 1-cyclopropylvinyl-kations

1-Bromo-1-cyclopropyl-2-methyl-1-propene (7) does not react with cyclohexene and AgSbF₆ with formation of the expected cycloadduct 9. The first generated cyclopropylvinyl-cation 8 rearranges to the allyl-cation 10 which after addition to the olefins cyclohexene and 2,3-dimethyl-2-butene (19) via unusual rearrangements gives the dienes 17 and 20 respectively.     

Gas phase reaction of NO2 with alkenes and dialkenes

The kinetics of the gas phase reactions of NO₂ with a series of organics have been studied at 295 ± 2 K. It was observed that only 2,3-dimethyl-2-butene and the conjugated dialkenes studied reacted at observable rates, with rate constants which ranged from 1.5 × 10^?20 cm³ molecule^?1 s^?1 for 2,3-dimethyl-2-butene to 1.3 × 10^?17 cm³ molecule^?1 s^?1 for α-phellandrene. These rate constants are compared with the available literature data and the mechanisms of these reactions are discussed.     

Spectral assignments for the aldose reductase inhibitor 4(S)-2,3-dihydro-6-fluoro-2(R)-methylspiro[chroman-4,4'-imidazoline]-2',5'-dione and its synthetic intermediates

The 1H and 13C NMR chemical shifts of the aldose reductase inhibitor 4(S)-2,3-dihydro-6-fluoro-2(R)-methylspiro[chroman-4,4'-imidazoline]-2',5'-dione, methylsorbinil, and its seven synthetic intermediates, have been completely assigned on the basis of DEPT, COSY, g-HSQC and g-HMBC. All C--F coupling constants from one-bond to four-bond in the 13C NMR spectra and H--F and H--H coupling constants from three-bond to four-bond in 1H spectra were obtained.     

The Radiation Polymerization of 4-Methyl-1-pentene, 2-Methyl-1-butene,and 2,3-Dimethyl-1-butene under Conditions of Extreme Dryness

The γ-ray initiated polymerization of 4-methyl-1-pentene, 2-methyl-1-butene, and 2,3-dimethyl-1-butene has been studied under conditions of extreme dryness. Only low yields of oily low molecular weight polymers were obtained. It is suggested that the low propagation rate constants are responsible for the results obtained.     

Isomerism in jet-cooled 1-cyanonaphthalene complexes

The effect of complexation on the first electronic transition of 1-cyanonaphthalene has been studied for complexes with aprotic polar solvents (acetonitrile, diethylether) or olefins (2-methyl-2-butene, 2,3-dimethyl-2-butene). In both cases, isomerism has been evidenced. With polar solvents, two strong absorption bands appear in the 0 ₀ ⁰ region, one being shifted to the red and the other one to the blue side of the bare cyanonaphthalene transition. These two bands have been assigned to two isomeric forms involving specific interactions between the solvent and the cyanonaphthalene molecule. These isomers have been shown to interconvert at higher vibronic energies. With the 2,3-dimethyl-2-butene a broad absorption band leading to a red shifted fluorescence has been observed and assigned to an exciplex. With the 2-methyl-2-butene, one observes the superposition of narrow and broad bands in the excitation spectrum. These two systems have been assigned to two isomeric forms, one of them crossing to an exciplex in the excited state. At higher vibronic energy, emission from the two conformers is observed.     

Photoaddition reactions of 1,4-diphenylbutadiyne with olefins

1,4-Diphenylbutadiyne(DPB) and several olefins such as 2,3-dimethyl-2-butene, 1,4-cyclohexadiene and dimethyl fumarate were irradiated with 300 nm UV light to obtain interesting cross-cycloaddition products.     

Synthesis and Polymerization of Some New Bis-Triazolinediones: A Stability Study of 4-Substituted Triazolinediones

Three new bis-triazolinediones, 3,3′-dimethyl-4,4′-bis-[3,5-dioxo-1,2,4-triazoline-4-yl]biphenyl, t-1,4-bis-[3,5-dioxo-1,2,4-triazoline-4-yl]methyl cyclohexane, and 4,4′-bis-[3,5-dioxo-1,2,4-triazoline-4-yl] phenyl ether, were synthesized from their corresponding bis-amines or bis-isocyanates. The compounds were identified by their quantitative ene reaction with 2,3-dimethyl-2-butene. The high degree of reactivity of the triazoline moiety makes solvent selection for reaction media rather difficult. This fact prompted a study of rates of reaction with a variety of polar and nonpolar solvents, including halogenated aliphatics, aromatics, tetrahydrofuran (THF), and N,N-dimethylformamide (DMF). The compounds exhibited reasonable stability in the halogenated solvents, as well as in the aliphatic and aromatic hydrocarbons, but they underwent reaction with THF and DMF. The structure of the reaction product of N-phenyl-1,2,4-triazoline-3,5-dione in DMF solution was determined, and a mechanism for product formation was proposed. Two of the bis- triazolinediones were polymerized via a base-catalyzed condensation mechanism which eliminates N₂ from the triazolinedione ring.     

C2 molecule: formation from bromoacetylene and reactions with cyclohexene or 2,3-dimethyl-2-butene

The C₂ molecule (1,2-ethynediyl) has been prepared by dehydrohalogenation of 1,2-dibromoethylene with an excess of potassium tert-butoxide in 2,3-dimethyl-2-butene as the solvent and the reagent. The major products of this reaction were 2,3-dimethylbut-3-en-2-ol and dibromoacetylene.     

Nickel and iron complexes with oxazoline- or pyridine-phosphonite ligands; synthesis, structure and application for the catalytic oligomerisation of ethylene

The bis(oxazolinyl)phenylphosphonite ligand (bis(4,4-dimethyl-2-(1-hydroxy-1-methylethyl)-4,5-dihydrooxazole)phenylphosphonite, NOPONMe2)) and the new pyridine-phosphonite ligand (2-ethyl(1'-methyl-1-hydroxy)pyridine-6H-dibenz[c,e][1,2]oxaphosphorin) have been used for the preparation of the mononuclear complexes [NiCl2(NOPONMe2)] 18 and [NiCl2(6)2] 19, respectively, which catalyze the oligomerisation of ethylene with activities up to 57300 mol C2H4 mol Ni(-1) h(-1) (19 in the presence of only 6 equivalents of AlEtCl2). The selectivities for C4 dimers were as high as 90% (18 in the presence of only 2 equivalents of AlEtCl2) with selectivities for 1-butene of 21-22% of the C4 fraction. In the presence of 400 or 800 equivalents of MAO as cocatalyst, complex 19 yielded turnover frequencies of 7400 mol C2H4 mol Ni(-1) h(-1) and 13200 mol C2H4 mol Ni(-1) h(-1), respectively. The selectivities for 1-butene and ethylene dimers were similar to those obtained with AlEtCl2. The fact that 19 with a cyclic phosphonite moiety leads to higher activities and selectivities than 18 which contains an acyclic phosphonite group underlines the importance of the ligand on the catalytic properties of its metal complex. An unprecedented dinuclear iron complex [FeCl2(4,4-dimethyl-2-[(1-hydroxy-1-methyl)ethyl]-4,5-dihydrooxazolate)]2 20 was also obtained which contains two pentacoordinated metal centers coordinated by a bridging-chelating oxazoline-alcoholate. Complexes 18-20 are paramagnetic in solution, as determined by the Evans method.     

Zur Synthese sulfonierter Derivate von 2,3-Dimethylanilin und 3,4-Dimethylanilin

On the Synthesis of Sulfonated Derivatives of 2,3-Dimethylaniline and 3,4-Dimethylaniline Baking the hydrogensulfate salt of 2,3-dimethylaniline ( 1 ) or of 3,4-dimethylaniline ( 2 ) led to 4-amino-2,3-dimethylbenzenesulfonic acid ( 4 ) and 2-amino-4,5-dimethylbenzenesulfonic acid ( 5 ), respectively (Scheme 1). The sulfonic acid 5 was also obtained by treatment of 2 with sulfuric acid or by reaction of 2 with amidosulfuric acid. 3-Amino-4,5-dimethylbenzenesulfonic acid ( 3 ) and 5-Amino-2,3-dimethylbenzenesulfonic acid ( 6 ) were prepared by sulfonation of 1,2-dimethyl-3-nitrobenzene ( 9 ) to 3,4-dimethyl-5-nitrobenzenesulfonic acid ( 11 ) and of 1,2-dimethyl-4-nitrobenzene ( 10 ) to 2,3-dimethyl-5-nitrobenzenesulfonic acid ( 12 ), respectively, with subsequent Béchamp reduction (Scheme 1). Preparations of 2-amino-3,4-dimethylbenzenesulfonic acid ( 7 ) and of 6-amino-2,3-dimethylbenzenesulfonic acid ( 8 ) were achieved by the sulfur dioxide treatment of the diazonium chlorides derived from 3,4-dimethyl-2-nitroaniline ( 24 ) and from 2,3-dimethyl-6-nitroaniline ( 31 ) to 3,4-dimethyl-2-nitrobenzenesulfonyl chloride ( 29 ) and 2,3-dimethyl-6-nitrobenzenesulfonyl chloride ( 32 ), respectively, followed by hydrolysis to 3,4-dimethyl-2-nitrobenzenesulfonic acid ( 30 ) and 2,3-dimethyl-6-nitrobenzenesulfonic acid ( 33 ), and final reduction (Scheme 3). Compound 7 was also synthesized by reaction of 4-chloro-2,3-dimethylaniline ( 23 ) with amidosulfuric acid to 2-amino-5-chloro-3,4-dimethylbenzenesulfonic acid ( 20 ) and subsequent hydrogenolysis (Scheme 2). 4′-Bromo-2′, 3′-dimethyl-acetanilide ( 13 ) and 4′-chloro-2′, 3′-dimethyl-acetanilide ( 14 ) on treatment with oleum yielded 5-acetylamino-2-bromo-3,4-dimethylbenzenesulfonic acid ( 17 ) and 5-acetylamino-2-chloro-3,4-dimethylbenzenesulfonic acid ( 18 ), respectively. Their structures were proven by hydrolysis to 5-amino-2-bromo-3,4-dimethylbenzenesulfonic acid ( 21 ) and 5-amino-2-chloro-3,4-dimethylbenzenesulfonic acid ( 22 ), followed by reductive dehalogenation to 3 .