A general structural principle for organic compounds that have the capacity for two-stage electron transfer is based on the following reaction sequence:X+CH=CHj,X 5 In this scheme one or both of the entities X may be replaced by Y'. The radical partners in these systems often have very high thermodynamic stability. The choice of the end groups X and Y, (partial) inclusion of n-systems in rings, alteration of the number of vinylene groups,

Ein allgemeines Strukturprinzip fur organische Verbindungen, die zur zweistufigen Elektronenubertragung befahigt sind, geht aus der folgenden Reaktionssequenz hervor:

The "best" plane through C(3)-C(7)-0(1)-N is at an angle of 18 to the f3-lactam ring, and at an angle of 41 to the benzene ring. The lactam ring and benzene ring are inclined at an angle of 56 to each other. The deviation of the molecule from the favorable planar resonance form appears to be due to steric factors. The hydrogen atom on C(2) approaches to within 2.75 A of 0(2), that on C(4) to within 2.71 A of O(1); on the other hand the sum of the van der Waals radii in both cases is 2.7 A. A few Characteristic bond lengths (in A) are given in the Figure (average standard deviation: 0.01 5 A). Particularly striking is the large distance between C(8) and C(9), which has also been observed in another p-lactarn161. The C(10)-0(2) distance is unusually small for a carbon-oxygen double bond; this is also apparent from the carbonyl stretching vibration at 5.62 pm.

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Trimethylsilyl Cyanide -A Reagent for Umpolung, I Nucleophilic Acylation of Alkylating Reagents with Aromatic and Heteroaromatic AldehydesThe readily accessible adducts 7 from (hetero)aromatic aldehydes and trimethylsilyl cyanide are deprotonated by lithium diisopropylamide. The so formed anions 8 react with alkyl halides, dialkyl sulfates and alkyl tosylates producing 19 with inversion and without interfering elimination. From 19 the protective group is removed under mild conditions and ketones 20 are produced mostly in 80-90% yield. The scope of the reaction sequence with respect to (hetero)aromatic aldehydes and alkylating agents is demonstrated. Lithium ions are shown to cooperate in the smooth substitution of tert-butyl iodide by8. Within the given limits the described reaction sequence complements advantageously the known methods of nucleophilic acylation. A. Einfuhrung und ZielsetzungSpatestens seit Einfiihrung der Grignard-Reaktion ist dem Chemiker bekannt, daD sich das normale Reaktionsmuster eines Reaktanden (hier Alkylierungsmittel) durch ein Hilfsreagens (hier Magnesium) in sein Gegenteil verkehren lafit. Aber erst vor wenigen Jahren ist dieses Wissen zum allgemeinen Prinzip erweitert worden, das den treffenden Namen ,,Umpolung" erhielt ' ). Schrittmacher dieser Entwicklung war die Umpolung von Aldehyden zu nucleophilen Acylierungsmitteln ') mit dem Synthon A.Als wichtigste Reagentien zur nucleophilen Acylierung, soweit sie aus Aldehyden darstellbar sind, durften 1 ' ), 2 7, und 4') gelten. Eine Ausnahmestellung nimmt die elegante katalytische Erzeugung des Synthons A mittels C~a n i d -~) oder Thiazolium-ylid-