5,5-Dimethyl-l-pyrroline 1-oxide

Simple nonconjugated nitrones have a strong absorption maximum in the UV at around 230 nm. Acyclic nitrones are, in general, photo-chemically cyclized to the corresponding oxaziridines.148 The cyclic nitrone, 5,5-dimethyl-l-pyrroline 1-oxide (164) is similarly converted into the oxaziridine (165) by photolysis in ethanol/cyclohexane solution,146 and several 2-substituted 1-pyrroline 1-oxides were subsequently found to undergo the same cyclization in cyclohexane solution.147... 

The principal product of prolonged irradiation of the oxaziridine (175), formed from 3,5,5-trimethyl-l-pyrroline 1-oxide, is 3,5,5-trimethyl-2-pyrrolidone (176). In this instance, the 1,2-shift of a hydrogen atom, possible in pyrrolidines not containing an alkyl substituent on C-2, is preferable to pyrrolidine ring cleavage. A similar effect is observed in the photolysis of 5,5-dimethyl-l-pyrroline 1-oxide.147... 

The reaction of 5,5-dimethyl-l-pyrroline 1-oxide with dimethylketene N-phenylimine leading to pyrrolo[l,2-a]imidazol-2(3H)-ones (190) proceeds via initial formation of zwitterion (188). Subsequent sigmatropic rearrangement of (188) gives zwitterion (189), capable of undergoing ring closure to (190) (79JOC4543). 

Bronchoalveolar lavage cells (lx 10 ) suspended in Dulbecco s phosphate buffered saline (0.5 ml) containing 5,5-dimethyl-l-pyrroline-1-oxide (DMPO 100 mM) in duplicate samples, one with and one without superoxide dismutase (500 imits/ml) by electron paramagnetic resonance measurements recorded superoxide anion generation at sites of antigen challenge (Sanders et al. 1995). 

FIGU RE 10.1 The structure of DMPO. The diamagnetic compound 5,5-dimethyl-l-pyrroline-iV-oxide reacts with an unstable radical R to form a relatively stable radical adduct. 

Spectroscopic evidence for peroxy radical 51 was obtained from ESR. Spin trapping studies monitored by ESR have demonstrated that 02 reacts efficiently with 2-nitrobenzenesulfonyl chloride and results in the formation of the peroxy radical intermediate 51 (equation 88). The 5,5-dimethyl-l-pyrroline-l-oxide (DMPO) spin adduct of 51 shows the hyperfine coupling constants, aN = 1.8 G and aH = 10.1 G. 

Thirty milligrams of the Pt/C catalyst or Ketjenblack was dispersed in 1ml of ultrapure water, which contained 200pi of 5,5-dimethyl-l-pyrroline-A-oxide (DMPO). Next, air which contained 1.3% hydrogen gas was bubbled into the... 

Oxidation of a sulfide to sulfoxide is known to be an electrophilic reaction, in contrast with nucleophilic oxidation of sulfoxide to sulfone. Since 2-nitrobenzenesulhnyl ehloride/K02 oxidizes sulfides to sulfoxides selectively, intermediate 48 must be the actual active intermediate. Moreover, in the presence of l,4-diazabicyclo[2.2.2.]octane (DABCO), which is a radical capturing reagent, the oxidation of methyl phenyl sulfide to the sulfoxide was inhibited. In order to further detect the intermediate 48, pure 5,5-dimethyl-1-pyrroline-l-oxide (DMPO) was used as a trapping reagent and spin adduct was obtained223. The ESR spectrum of the DMPO spin adduct was obtained by the reaction of 02 with 2-nitrobenzenesulfinyl chloride (hyperfine coupling constants, aH = 10.0 G and aN = 12.8 G). 

Let us report here the results of the reactions of 1-pyrroline-l-oxide and 5,5-dimethyl-1-pyrroline-l-oxide with acrylonitrile (Scheme 1 and Table 1) and maleonitrile (Scheme 2 and Table 2). In our regiochemical notation, A-adducts involve the a-carbon atom of the alkene in the new forming C - C bond, whereas... 

Hydroxyl radical was generated from Fenton reaction with the mixing of FeSO (2.27 iM) and H2O2 (227 iM). Superoxide radical was generated from a hypoxanthine-xanthine oxidase (HPX-XOD) reaction system. Both hydroxyl radical and superoxide were trapped by 5,5-dimethyl-1-pyrroline-l-oxide (DMPO). 

Kamibayashi M, Oowada S, Kameda H et al (2006) Synthesis and characterization of a practically better DEPMPO-type spin trap, 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-l-pyrroline N-oxide (CYPMPO). Free Radio Res 40 1166-1172... 

The /V -hydroxylamino compounds (404) and (405), obtained from the reaction of tert-butyl acetate with 3,4-dihydroisoquinoline-A-oxide or 5,5-dimethyl-pyrroline-/V-oxide, when boiled in methylene chloride in the presence of triphenylphosphine, carbon tetrachloride and triethylamine, are transformed to (1,2,3,4- tetrahydroisoquinolin-l-ilidene) acetate (406) or (pyrrolidin-2-ilidene) acetate (407) (Scheme 2.181) (645). 

Other than giving a very good account of the experimental qualitative behaviour, the above results probably offer a reasonable quantitative evaluation of the leacbon parameters. The apparent activation free enthdpy of the reaction of 1-pyrroline-1-oxide and 5,5-dimethyl-1-pyrroline-l-oxide with acrylonitrile have been meas-ured 2 in cyclohexane (20.4 0.4 and 21.7 0.4 kcal mol, respectively) and in di-chloromethane (22.4 0.2 and 23.010.8 kcal mol ) at 298K the rate constants for the reactions of H-nitrone have not been measured, but it can be stressed that N-monosubstituted nitrone, e.g, t-Bu-nitrone, exhibits a high reactivity in 1,3-dipolar cycloadditions, which is similar to that of 1-pyrroline-l-oxide so that the evaluations of Table 6 emerge to be surprisingly good. Moreover, the activation entropy of the reaction of 5,5-dimethyI-1-pyrroline-l-oxide with acrylonitrile in cyclohexane has been estimated -31,9 eu, a value which is well reproduced by our calculations in the gas-phase (-33.4, -31.1, footnote of Table 6). 

Aq. hydrazine added dropwise with stirring below 55° to a mixture of 4-methyl-4-nitro-3-phenyl-l-(3-pyridyl)-l-pentanone and Raney-Ni, stirring continued 2 hrs. 5,5-dimethyl-4-phenyl-2- (3-pyridyl) -Zl -pyrroline 1-oxide. Y 70-75%. F. e. s. M. G. Kloetzel et al.. Am. Soc. 83, 1128 (1961). 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

---