Dimethyldioxirane ~~~~~The oxygen transfer to the enamines la-f by dimethyldioxcorresponding a-amino ketone 3c (hydride shift) and the amirane (DMD) in acetone solution leads to the a-amino epoxides ides 4d -f (alkyl shift). The a-[bis(trimethylsilyl)]amino epox2a-f. The stability of the a-amino epoxides 2a-f depends ides 2a, b represent the first observable enamine oxides and only on the type of substitution at the nitrogen atom. Thus, emphasize the value of stabilizing such labile epoxides while the epoxides 2a, b could be characterized spetroscopi-through disilylation of the enamine nitrogen atom. cally, the epoxidation of the enamines 1 c -f resulted in the In a recent publication [11 we have demonstrated that dimethyldioxirane reacts with enamines, which bear an a-hydrogen atom at the C -C double bond, to form amino-substituted 1,Cdioxanes. Unfortunately, the intermediary epoxides could not be detected spectroscopically even at low temperatures. The oxygen transfer by dimethyldioxirane occurred selectively at the double bond independent of the amino group, and the observed 1,4-dioxanes result from dimerization of the labile enamine oxides through the mesomerically stabilized 1,3-dipoles. Alternatively, analogous to epoxides which bear a + M substituent, a-amino epoxides should rearrange by an 1,2-hydride shift to the corresponding carbonyl products [*]. Indeed, such rearrangement is observed in the oxidation of enamines by tripletIn this case, attack of molecular oxygen at the C-C double bond forms, besides C-C cleavage products, also a-amino ketones, which have been postulated to be derived from their intermediary a-amino epoxides. Moreover, the formation of the indolinone in the deoxygenation of an indole dioxetane[61 can be interpreted in terms of the corresponding epoxide as intermediate. To date, no direct experimental evidence for u-amino epoxides has been published. Presumably, the destabilizing effect of the a-amino substituent is responsible and, thus, it is not surprising that recently an a-amino epoxide was reported"', in which the destabilizing effect of the electron-rich amino group was arrested through substitution by an electron-withdrawing group.Since silylation is known to diminish dramatically the basicity and nucleophilicity of amines [loal, it was of interest to assess whether such substitution is sufficient to observe N-silylated a-amino epoxides and, if successful, explore the chemical behavior of such hitherto unknown epoxides. Herein we demonstrate that the novel concept of stabilizing a-amino epoxides through disilylation of the enamine nitrogen atom is indeed an effective tool to observe labile enamine oxides. Furthermore, an effort was made to detect intact Nacylated indole epoxides. Results and DiscussionEpoxidation of the bis(trimethy1sily)-substituted enamines 1 a, b by dimethyldioxirane (DMD) afforded the corresponding a-amino epoxides 2a,b (Scheme l), as manifested by low-temperature NMR spectroscopy. The characteristic 'H chemical shifts at 6 = 2.74 for 2 a (R3 = H) and 2.80 ...

Nitrobenzene, α‐nitronaphthalene, m‐dinitrobenzene, 1,3,5‐trinitrobenzene, m‐nitrobenzophenone, m‐nitrobenzonitrile, methyl m‐nitrobenzoate and m‐nitro diphenylsulphone can be hydroxylated with cumene or tert‐butyl hydroperoxide in dipolar aprotic solvents in the presence of strong bases. The hydroxyl group is introduced preferably in p‐position to the nitro group. Attempts to hydroxylate benzophenone, anthraquinone, 2‐ethyl anthraquinone, anthraquinone 2‐sulphonate, benzonitrile and diphenyl sulphone under the same conditions failed. 1‐Nitroanthraquinone delivered 1‐hydroxy, 1,2‐dihydroxy and 1,4‐dihydroxy anthraquinone.

The 1,4-dioxanes 3a-f, which constitute dimers of the enamine epoxides 2a -f, were obtained in excellent yields as crystalline products during the oxygen transfer to the corresponding enamines by dimethyldioxirane (DMD) in acetone.

The relative chain propagation constants and the regioselectivities of the oxidations of o‐cymene and 2‐isopropyl‐1,4‐dimethylbenzene were determined by competitive oxidations of the hydrocarbons with cumene. As expected, the reactivity of the tertiary CH bond of the isopropyl group is considerably decreased by o‐methyl groups. Also in α‐isopropylnaphthalene a considerable decrease in the reactivity of the tertiary CH bond takes place. The decrease of the chain propagation constants effects a decrease of the oxidabilities of o‐substituted isopropyl aromatics. In the case of the methyl isopropyl benzenes the increase of the chain termination constants by primary peroxy radicals must also be taken into consideration. This results in a decrease of the oxidabilities which can be observed even in p‐cymene (in comparison with cumene).