Two electron-deficient dienes were reacted with a series of twelve electron-poor and electron-rich dienophiles to give, in some cases, the corresponding Diels-Alder adducts. Clear differences in the roles played by the two frontier orbital interactions emerged. It was demonstrated that in the case of normal Diels-Alder cycloadditions, the FMO theory could predict the relative reactivities between dienophiles, while in the case of inverse-electron demand Diels-Alder reactions, it could not. It was shown that the dissymmetry in electron-rich dienophiles increases their reactivities.

This study suggests that EGCG may be a useful adjuvant therapeutic agent for the treatment of breast cancer.

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Inter- and intramolecular [4 + 1]-annulations between dialkoxy carbenes and electron-deficient dienes afford mono- or bicyclic products in moderate to good yield.

[reaction: see text] Substituted vinylidene zinc carbenoids undergo a Fritsch-Buttenberg-Wiechell rearrangement. The migratory aptitude of the two groups R/R1 was studied by 13C labeling experiments and depends on the degree of substitution in R and R1 groups and on the presence of an oxygen atom in the allylic position.

BackgroundSleep patterns and habits in high school students in Iran have not been well studied to date. This paper aims to re-address this balance and analyse sleep patterns and habits in Iranian children of high school age.MethodsThe subjects were 1,420 high school students randomly selected by stratified cluster sampling. This was a self-report study using a questionnaire which included items about usual sleep/wake behaviours over the previous month, such as sleep schedule, falling asleep in class, difficulty falling asleep, tiredness or sleepiness during the day, difficulty getting up in the morning, nightmares, and taking sleeping pills.ResultsThe mean duration of night sleep was 7.7 h, with no difference between girls, boys, and school year (grade). The mean time of waking in the morning was not different between genders. About 9.9% of the girls and 4.6% of the boys perceived their quality of sleep as being bad, and 58% of them reported sleepiness during the day. About 4.2% of the subjects had used medication to enhance sleep. The time of going to bed was associated with grade level and gender. Sleep latency was not associated with gender and grade leve, l and 1.4% experienced bruxism more than four times a week.ConclusionOur results are in contrast with that of previous studies that concluded sleep duration is shorter in Asia than in Europe, that boys woke-up significantly later than girls, and that the frequency of sleep latency category was associated with gender and grade level. The magnitude of the daytime sleepiness, daytime sleepiness during classes, sleep latency, and incidences of waking up at night represent major public health concerns for Iran.

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An efficient three steps process for converting aliphatic ketones to the homologous gem-bromochloro, or gem-dibromo alkenes is presented.