1.3- dioxol 2,2-dimethyl

Dioxol 2,2-Dimethyl-4-ethoxy-carbonyl- E19b, 1316 (Carben-... 

Dioxol 2,2-Dimethyl-5-(l-hydroxy-propyl)-4-methoxycar-bonyl- E14a/1, 697... 

Little l-//-pentafluoropropylene is produced anymore, because its existence IS no longer justified as a less stable alternative to HFP m VDF-based elastomers, given the expiration of patents covenng the basic VDF/HFP/(TFE) compositions Perfluoro-1,1-dimethyl dioxole is prepared from hexafluoroacetone and ethylene oxide in four propnetary steps [5] (equation 4)... 

Tetrafluoroethylene-Perfluoro(2,2-dimethyl-l,3-dioxole) Copolymers (Teflon AF)... 

Thenoines with urea in acetic acid give 4,5-bis(2,5-dimethyl-3-thienyl)-lH,3H-imidazol-2-one 239, whose treatment with acid chlorides affords photochromes 240 in good yields (02IZV1588). Thenoine 213 with an excess of l,l -carbonyldiimidazole produces l,3-dioxol-2-ones 241 in high yields (02IZV1588). However, thenoine with l,l -thiocarbonyldiimidazole gives 4,5-bis (2,5-dimethyl-3-thienyl)-l,3-oxathiol-2-one 242 instead of the expected thione (04ZOR1743) (Scheme 69). 

Unexpected reactions occur when benzo[c]furans are treated with o-quinones. Tedder and co-workers reacted 5,6-dimethyl-l,3-diphenyl-benzo[c]furan (210) with o-benzoquinone (211, X = H) and o-chloranil (211, X = Cl) to give dioxoles (212). Subsequent investigations have shown that [714 + 7i4]-cycloadducts (213) are also formed other benzo[t]furans... 

Hydroxy-3-methoxy-[(2S,3aR,3bS, 6aR,9aR,9bR, 10R,11aR)-3a,3b,6,6a,9a,10,11,11a-octahydro-6a-hydroxy-8,10-dimethyl-11a-(1-methyl-ethenyl)-7-oxo-2-(phenyl-methyl)-7H-2,9p-epoxy-azuleno[5,4-e]-1,3-benzo-dioxol-5-yl]benzeneacetic acid, C37H40O91 Mr 628.71. 

A similar method has been used for the epoxidation of nonconjugated diene 3, prepared from perfluoro(2,2-dimethyl-l, 3-dioxole).104... 

In certain cases benzene will undergo photocycloaddition to oxygen and sulfur heterocycles. The two major photoproducts of irradiation of a mixture of furan and benzene are adducts 356 and 357, arising, respectively, by [ 2 + 2] and [ 4 + 4] cycloaddition processes.306 Irradiation of benzene and 2,2-dimethyl-l,3-dioxol (358) similarly affords adducts 359 and 360, together with dimer 361.307 Thiochromone 1,1-dioxide also undergoes photoaddition to benzene.308... 

Para photocycloaddition of arenes to the benzene ring was first reported in 1971 by Wilzbach and Kaplan [7] as a minor process accompanying ortho and meta photocycloaddition. Since that time, relatively few cases of para photocycloaddition have been described. Para adducts were found as minor products from benzene with cyclobutene [8], ra- 3,4 - dimethyIcycIobu(ene [9], vinylene carbonate [10], 2,3-dihydropyran [11,12], and 1,3-dioxole [13,14] and from a,a,a-tri-fluorotoluene with vinylene carbonate [15], Intermolecular para photocycloadducts were major products from the irradiations of benzene and allene [16,17], benzene and cyclonona-1,2-diene [16,17], and from fluorobenzene and cyclopentene [18], Intramolecular para photocycloadducts were found as major products from the irradiations of phenethyl vinyl ether [19-21] (Scheme 3) and 2,3-dimethyl-6-phenylhex-2-ene [22], No detailed mechanistic investigations have been published. 

In 1977, Scharf and Mattay [123] found that benzene undergoes ortho as well as meta photocycloaddition with 2,2-dimethyl-1,3-dioxole and, subsequently, Leismann et al. [179,180] reported that they had observed exciplex fluorescence from solutions in acetonitrile of benzene with 2,2-dimethyl-l,3-dioxole, 2-methyl-l,3-dioxole, 1,3-dioxole, 1,4-dioxene, and (Z)-2,2,7,7-tetram-ethyl-3,6-dioxa-2,7-disilaoct-4-ene. The wavelength of maximum emission was around 390 nm. In cyclohexane, no exciplex emission could be detected. No obvious correlation could be found among the ionization potentials of the alkenes, the Stern-Volmer constants of quenching of benzene fluorescence, and the fluorescence emission energies of the exciplexes. Therefore, the observed exciplexes were characterized as weak exciplexes with dipole-dipole rather than charge-transfer stabilization. Such exciplexes have been designated as mixed excimers by Weller [181],... 

Leismann et al.[182] have recognized this problem in their publication of 1984, in which they describe a thorough and detailed investigation of the kinetics of formation and deactivation of exciplexes of. S) benzene or toluene and 1,3-diox-ole, 2,2-dimethyl-l,3-dioxole, and 2,2,4-trimethyl-l,3-dioxole. The evolution in time of monomer and exciplex fluorescence after excitation using a nanosecond flash lamp was analyzed, and again it was concluded that the formation of exciplexes is diffusion controlled their decay proceeds mainly (>90%) via radiationless routes. The polar solvent acetonitrile enhances radiationless deactivation, possibly by promoting radical ion formation. Because decay of benzene fluorescence is essentially monoexponential, dissociation of the exciplex into Si benzene and dioxole is negligible. 

In cyclohexane, no exciplex emission is observed. Leismann et al. [182] have measured the quantum yields of meta and ortho adduct formation from benzene and 2,2-dimethyl-l,3-dioxole in cyclohexane at various concentrations of the... 

Freshly prepared sodium methoxide (0.1 ml of a 1 M solution in methanol, 10 mmol) was added dropwise to a solution of cis-3,5-cyclohexadiene-l,2-diol (112 mg, 1 mmol) in dimethyl carbonate (1.7 ml) and methanol (0.2 ml) at RT under argon, and stirred for 20 min. A small aliquot was removed, solvent evaporated in vacuum (bath T 22°C) and the resulting solid was washed with a small volume of chilled (-20°C) ether and chilled (-20°C) petrol (b.p. 30°-40°C) to afford the 3a,7a-dihydrobenzo[l,3]dioxol-2-one (cyclic carbonate) as a beige-coloured solid, mp 90°C (dec.). 

To a solution of 7-methanesulfonyloxy-2,2-dimethyl-3a,6,7,7a-tetrahydro-benzo[l,3]dioxole-carboxylic acid methyl ester (35.85 g, 117 mmol) in methanol (500 ml) was added p-toluenesulfonic acid (1.11 g, 5.85 mmol, 5 mol %) and the solution was refluxed for 1.5 h and was evaporated. The residue was redissolved in methanol (500 ml) and was refluxed an additional 4 h. The solvent was evaporated and the crude oil was triturated with diethyl ether (250 ml). After completing the crystallization overnight at 0°C, the solid was filtered and was washed with cold diethyl ether, and dried to afford 3,4-dihydroxy-5-methanesulfonyloxy-cyclohex-l-enecarboxylic acid methyl ester (24.76 g) as a white solid. Evaporation of the filtrate and crystallization of the residue from methanol/diethyl ether gave an additional 1.55 g. Obtained 26.3 g (85%) of the 3,4-dihydroxy-5-methanesulfonyloxy-cyclohex-l-ene-l-carboxylic acid methyl ester. 

Fig. 4. Absorption spectra with benzil (A, 7) (a) of 3A (solid line, end of pulse) and of A- (dashed line, after 100ns in the presence of tetraethoxyethene (5) (0.01 M) in acetonitrile, and (b) in acetone in the presence of 4,5-dimethyl-l,3-dioxole (5) (0.02 M) (o, end of pulse) and after 200 ns in the absence ( ) and presence (a) of LiClO (0.4 M) (cf. [33, 36])...

There has been no effort to study systematically a series of compounds. The lower dioxoles and oxathioles are liquids, insoluble in water but soluble in most organic solvents. 1,3-Dioxole boils at 51 °C at atmospheric pressure, while 2,2-dimethyl substitution raises this to 72-73 °C. No boiling point has been reported for 1,2-dioxolane and the only report for 1,2-oxathiolane indicates that it codistills with chloroform at 20 °C (0.1 mmHg). 1,3-Dioxolane boils at 75 °C (760 mmHg) and the introduction of sulfur raises the boiling point such that 1,3-oxathiolane boils at 132-136 °C (760 mmHg). 

The interactions of a-olefins or styrene with sulfur dioxide (16) or a-olefins (24, 58, 78), frans-stilbene (64), styrene (1,63), p-dioxene (52), 2,2-dimethyl-l,3-dioxole (17), or alkyl vinyl ethers (1, 63) with maleic anhydride yield charge transfer complexes which are stable and generally readily detectable either visually or by their ultraviolet absorption spectra. However, under the influence of a sufficiently energetic attack in the form of heat or free radicals, the diradical complexes open, and alternating copolymers are formed. 

In contrast, dipolar aprotic solvents possess large relative permittivities (sr > 15), sizeable dipole moments p > 8.3 10 ° Cm = 2.5 D), and average C.f values of 0.3 to 0.5. These solvents do not act as hydrogen-bond donors since their C—H bonds are not sufficiently polarized. However, they are usually good EPD solvents and hence cation sol-vators due to the presence of lone electron pairs. Among the most important dipolar aprotic solvents are acetone, acetonitrile [75], benzonitrile, A,A-dimethylacetamide [76, 77], A,A-dimethylformamide [76-78], dimethylsulfone [79], dimethyl sulfoxide [80-84], hex-amethylphosphoric triamide [85], 1-methylpyrrolidin-2-one [86], nitrobenzene, nitro-methane [87], cyclic carbonates such as propylene carbonate (4-methyl-l,3-dioxol-2-one) [88], sulfolane (tetrahydrothiophene-1,1-dioxide) [89, 90, 90a], 1,1,3,3-tetramethylurea [91, 91a] and tetrasubstituted cyclic ureas such as 3,4,5,6-tetrahydro-l,3-dimethyl-pyr-imidin-2-(l//)-one (dimethyl propylene urea, DMPU) [133]. The latter is a suitable substitute for the carcinogenic hexamethylphosphoric triamide cf. Table A-14) [134]. 

National Institnte of Standards and Technology polyamide polyarylsnlfone perflnoroalkylvinyl ether polychlorotriflnoroethylene perflnoro-2,2-dimethyl dioxole polyethylene polyethylsnlfone... 

DIMETHYL-l. 3-BENZDIOXOL-4-YL-N-METHYL-CARBAMATE 2,2-DIMETHYLBENZO-l,3-DIOXOL-4-YL METHYLCARBAMATE 2,2-DIMETHYL-4-(N-METHYLAMINOCARBOXYLATO)-l,3-BENZODIOXOLE... 

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