No abstract

CH2=C(CH,)C(CH,)=CHZ, 513-81-5; CH,=C(OSiMe,)CH=CH,, 38053-9 1-7; CH,=C(OSiMe,)CH= CHOMe, 59414-23-2; CH3(CHZ),C=CH, 627-19-0; CH3CH2C=CC-H,CH,, 693-02-7; 1,3-~yclopentadiene, 542-92-7; 1,3-~yclohexadiene, 592-57-4; [ [2-(trimethylsilyl)bicyclo[2.2.2]octa-2,5-dien-3-yl]methoxymethylene]pentacarbonylchromium, 923 14-89-1; [ (2,4,5-trimethylcyclohexa-l,4-dien-1-y1)methoxymethylenel tetracarbonylchromium, 923 14-91-5; [ [2-methyl-6-methoxy-4-(trimethylsiloxy)cyclohexa-1,4-dien-lyl)methoxymethylene]pentacarbonylchromium, 923 14-92-6.Spectral and physical characterization of all new compounds in addition to experimental procedures are included (14 pages). Ordering information is given on any current masthead page. Abstract:The photoreduction of N-methylphthalimide (NMP) in the presence of 2,3-dimethyl-2-butene (DMB) gives a pair of products (1 and 2) which could formally arise by hydrogen abstraction by the imide followed by coupling of the resultant radical pair at either of the two allylic positions on the 1,1,2-trimethylallyl radical. Sensitization and quenching studies have shown that these products arise from the singlet state of NMP and not the triplet as previously suggested. Isotope effect studies with deuterium labeled DMB indicate that the reaction most probably proceeds by initial electron transfer to give the radical cation-radical anion pair. The ion pair either colapses to a zwitterionic precursor to 1 (13) or proton transfers to give a radical pair which subsequently collapses to 2. Isotope effect experiments indicate that decay of 13 to NMP and DMB is an efficient process relative to product formation.The photochemistry of phthalimides in the presence of alkenes is characterized by four processes:' the addition to give benz-azepinediones (eq 1);2 electron transfer to afford radical ion pairs which are trapped by alcohols (eq 2);3 photoreduction (eq 3);4,5 0002-7863/84/1506-7567$01.50/0 0 1984 American Chemical Society 1568

Previous studies have shown that iV-methylphthalimide (NMP) reacts with alkenes to afford, in a few cases, oxetanes, along with products of alkene addition to the C(0)N bond and products arising from initial electron transfer. In this paper we explore the photochemistry of N-methylnaphthalene-2,3-dicarboximide (NMN). The photochemistry of NMN was studied in benzene, a solvent which we were unable to use with NMP due to solubility factors. In this solvent oxetanes were the major products found with several alkenes («-methylstyrene, diphenylethylene, styrene, trons-stilbene). In the case of trans-stilbene a novel 2 + 2 addition to the 1,2-bond of NMN was also observed to give a photochemically labile cyclobutane. In benzene solvent alkene addition to the C(0)N bond was never a major product. Also investigated was a series of alkenes in acetonitrile containing methanol in which the expected products obtained by trapping the electron-transfer-generated radical anion radical cation pair with methanol were found. In the case of 2,3-dimethyl-2-butene there was observed a pair of photoreduction products analogous to those observed with this alkene and NMP. A study of solvent polarity effects on the ratio of these photoreduction products supports the previous suggestion that one of these arises via proton transfer followed by coupling of the radical pair, whereas the other comes from a rare case of radical cation-radical anion coupling followed by intramolecular proton transfer in the resultant zwitterion. Fluorescence quenching data for NMN with a series of unsaturated hydrocarbons are presented, and these data are shown to correlate well with the Weller equation.

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N‐Methyl‐phthalimid (I) reagiert mit Methylstyrol (II) bei der Photolyse zu den Addukten (III)‐(VII).