ChemInform Abstract: 1,3‐ANIONIC CYCLOADDITIONS. XIII. ENDO‐EXO‐ISOMERIC CYCLOADDUCTS OF TRANS,TRANS‐1,3‐DIPHENYL‐2‐AZAALYLLITHIUM AND ACENAPHTHYLENE

Abstract

Das durch Umsetzung von N‐Benzyliden‐benzylamin mit Li‐diisopropylamid bei ‐60°C sowie durch thermische Ringöffnung von N‐Lithio‐cis‐ oder ‐trans‐2,3‐diphenylaziridin bei +65°C in THF‐Lösung darstellbare Azaallyl‐Li (I) cycloaddiert sich bei 0°C oder ‐70°C unter Retention an Acenaphthylen (II).

2-Azaallyl Anions, 2-Azaallyl Cations, 2-Azaallyl Radicals, and Azomethine Ylides

“…The observed diastereoselectivities were not as high, however, in the formation of 6,5-bicyclic ring systems ( 45e , 45f ). To rationalize the observed stereochemical outcome, the authors proposed a model in which the 2-azaallyl anions adopt a W-shaped conformation (Scheme , inset), in accord with Kauffmann’s earlier studies. ,, …”

“…As shown in Scheme 8, they found that the 1,3-diphenyl-2-azaallyl anion 6a, which was accessed via deprotonative ring-opening of aziridine 4, reacted with trans-stilbene (20), cis-stilbene (22), and acenaphthylene (25). 50,62 The relative configurations of the cycloadducts obtained from these reactions provided important mechanistic insights. 63 First, according to Woodward−Hoffmann rules, the ring-opening of cis-2,3-diphenylaziridine 4 should occur in a conrotatory fashion to afford Eimine isomer 6a′ as the product.…”

“…To rationalize the observed stereochemical outcome, the authors proposed a model in which the 2-azaallyl anions adopt a Wshaped conformation (Scheme 14, inset), in accord with Kauffmann's earlier studies. 50,62,67 In addition to unsaturated carbon−carbon bonds, semistabilized 2-azaallyl anions can engage with other types of πbonds via cycloaddition reactions. For example, reaction between 6a and diimide 47 in THF at room temperature generated the imidazoline product 48 (Scheme 15).…”