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. Can. J. Chem. 61, 2729 (1983).The relative acidities of fiteen aldimines and ketirnines have been measured in THF using either ' " nrnr spectroscopy or trapping experiments with methyl iodide. The pK,'s are found to vary over a range of more than four pK units. The effects of structure on acidity indicate the acid-weakening effect of alkyl substitution in ketirnines to be due to steric effects. This interpretation is supported by the results of ab ir~itio calculations. The data also permit a quantitative estimation of the preference for the syn configuration of lithiated irnines to be at least four kcal/rnol. The anti selectivity previously reported for the lithiation of endocyclic irnines can be accounted for by angular constraints, as indicated by both ab initio calculations and pK, data on this class of irnine.ROBERT R. FRASER, MONIQUE BRESSE, NOEMI CHUAQUI-OFFERMANNS, K. N. HOUK et N. G. RONDAN. Can. J. Chern. 61, (1983).On a rnesurC les aciditCs relatives de quinze aldirnines et cCtirnines dans le THF en faisant appel soit ii la spectroscopie rrnn du "C ou i des expkriences de trappage avec I'iodure de rnCthyle. On a trouvC que les pK, varient sur plus de quatre unites de pK. Les effets de structure sur I'aciditC indiquent que l'abaissernent de I'aciditC lors de la substitution alkyle dans les cCtCrnines serait dC i des effets stCriques. Cette interprktation est en accord avec les rCsultats de calculs ab initio. Les donnCes perrnettent aussi d'Cvaluer quantitativement, i au rnoins 4 kcal/rnol, la prCfCrence pour la configuration sytz des irnines IithiCs. On peut expliquer la sClectivitC anti rapportCe anterieurernent lors de la lithiation d'irnines endocycliques en faisant appel i des contraintes angulaires qui sont suggCrCes i la fois par les calculs ab initio et les donnCes de pK, sur cette classe de cornposCs.[Traduit par le journal]During the course of our investigations on the chemistry of lithiated aldimines (1) and ketimines (2) a number of unusual results were encountered for which satisfactory explanations required further experimental support. For example, with but two exceptions the lithiation of aldimines and ketimines gave exclusively anions having the syn configuration, the main exception being the endocyclic imines 9 to 12 which formed anti lithio derivatives only (3).2 A second striking feature of the lithiation of ketimines concerns the regioselectivity of the reaction. Just as had been observed earlier for ketone oximes (4), oxime ethers ( 3 , and hydrazones (6), lithiation is markedly favored at a primary vs. secondary carbon atom (7) or at a secondary vs. a tertiary one (2,8). This is anomalous too, in the sense that the stability differences at primary, secondary, and tertiary carbons are normally small and in the reverse order when a change of sp3 to sp2 hybridization is involved (9, 10).As a potential aid to our understanding these results, we set out to obtain quantitative information on the deprotonation reaction, that is, to measure the relative acidities of a variety of imines o...

The combined effects of radiation and sous-vide treatment of chicken breast meat were investigated with respect to survival and growth of Listeria monocytogenes, shelf life, thiamine content, and sensory qualities. Chicken breasts were inoculated with L. monocytogenes 81–861 (105 CFU/g), vacuum-packed, irradiated with electron beam (EB) up to 2.9 kGy, and cooked to an internal temperature of 65.6°C. Sous-vide treatment alone had marginal lethal effect on the L. monocytogenes; the residual inoculum reached 107 CFU/g after 8 weeks at 2°C. However, after the combined treatments of sous-vide and EB at 2.9 kGy, the organism remained undetectable during the 8-week storage period. Parallel studies on uninoculated breast meat revealed that sous-vide samples had a shelf life of less than 6 weeks without EB treatment, whereas samples that were irradiated and then received sous-vide treatment had a shelf life of at least 8 weeks. There was a slight reduction in thiamine levels as a result of the EB treatment, but there was essentially no additional loss of thiamine due to the subsequent sous-vide treatment and storage at 2°C. Electron-beam treatment had very little effect on the odor and flavor of the reheated samples. It was concluded that EB treatment combined with sous-vide treatment can greatly enhance the microbial safety and shelf life of chicken breast meat.

FUMINORI AKIYAMA, and NOEMI CHUAQUI-OFFERMANNS. Can. J. Chem. 59,705 (1981).The I3C chemical shifts in a variety of aldimines and in both acyclic and cyclic ketimines have been examined. A comparison of the shieldings at the a carbons in syn versus anti stereoisomers shows a consistent upfield shift of 8-11 ppm in the syn isomer. The greater magnitude found in imines vs. oximes or hydrazones is a clear indication of a steric origin for the differential shieldings. The shifts in the imines of cyclohexanones exhibited stereochemically dependent effects of methyl substitution, very similar to those in analogous oxime and hydrazone derivatives. Chemical shift differences in the syn isomers of the a-phenethylimines of chiral aldimines and ketimines allow a facile measurement of diastereomer ratios for such compounds.ROBERT R. FRASER, JACQUES BANVILLE, FUMINORI AKIYAMA et NOEMI CHUAQUI-OFFERMANNS. Can. J. Chem. 59,705 (1981). On a examine les deplacements chimiques du I3C de diverses aldimines et des cetimines acycliques et cycliques. En comparant le blindage au niveau des carbones en positions a des stCrCoisomkres syn et anti, on constante un dtplacement vers les champs forts de 8-1 1 ppm en faveur de I'isomere syn. La valeur plus forte observee pour les imines par rapport icelle des oximes ou des hydrazones est une nette indication de I'origine sttrique des blindages differentiels. Les deplacements observes dans les imines de cyclohexanones ont des effets qui dependent stereochimiquement de la substitution par les methyles et qui sont trks semblables a ceux des derives analogues d'oximes et d'hydrazones. Les differences de deplacement chimique des isomkres syn desa-phenethylimines d'aldimines et de cetimines chirales permettent de mesurer facilement les rapports de diastereoisomkres dans de tels composes.[Traduit par le journal]The 13C spectral characteristics of aldehydes and ketones have been thoroughly studied (1, 2) and more recently many of their carbonyl derivatives including oximes (3-9, hydrazones (5, 6), and oxime ethers (6) have received considerable attention. Another class of nitrogen-containing carbonyl derivatives which has not been studied to any significant extent is the imines, data on only a few aryl(7) and a few anti aldimine derivatives (8) having been reported. During the course of our studies on the alkylation of ketimines (9, 10) and aldimines (11, 12) we have had the opportunity to record a large number of spectra of both the syn and anti isomers. In this paper we wish to describe the spectral characteristics of a number of representative examples in order to demonstrate the capability of 13C nmr to reveal both configurational and conformational information for this class of compounds. In addition, the comparison of configurational effects with those previously observed in other species provides clear evidence for the dominance of steric factors in causing the large --differential syn-anti shifts. ExperimentalThe imines described herein have all been synthesized either from the parent ketone...

The demethylation of 7-methoxy-4-nitrobenzofuroxan by aqueous KOH gives rise to 7-hydroxy-4-nitrobenzofuroxan as well as 5-hydroxy-4-nitrobenzofuroxan, the latter being formed via a retro-Boulton–Katritzky rearrangement. The retro rearrangement also occurs on heating the potassium salt of 7-hydroxy-4-nitrobenzofuroxan in the solid state. In basic aqueous solution 5-hydroxy-4-nitrobenzofuroxan undergoes the normal Boulton–Katritzky rearrangement to yield 7-hydroxy-4-nitrobenzofuroxan. These processes are rationalized on the basis of a balance between electrostatic and steric interactions in the reactants and the products of rearrangement.