Neglected Aspects of Anthracenide (Anthracenidyl) Chemistry — Reactions with twoN-Benzoylaziridines

Abstract

153Single electron transfer (SET) reactions of N-acylaziridines with radical anions and other electron sources were prompted by a mechanistic problem [2]. Usually aziridino ketyls arise and homolyze to amidatoalkyl radicals [2 -7]. The final result can depend on substituents of the aziridine ring, on the acyl group and on the radical anion. 2-Phenylaziridines present a special case [6 -7]. Reactions with N-pivaloylaziridines were reported both with naphthalenidyl N ·¯ (naphthalenide) and with A ·[ 3], reactions of N-aroylaziridines with N ·¯ only [5]. After a very short notice [2], reactions of 1a,b with A ·ā re now fully described with steps and types of products usually ignored or even unknown in A ·¯ chemistry and therefore of possible importance for reactions with alkylating agents RX [8] (cf. introduction in [3]) that give alkylation in position 9 (and 10) of A ·¯ besides reduction (→ RH) and multi-step dimerization (→ RR) (Scheme 1). Tables 1 and 2 Table 1 indicates that this nearly insoluble product may have been lost during work-up [5]. This does not disturb a discussion of the other products. Counter ion Na + has been replaced by Li + in runs 6 and 7 that are dealt with separately. Results and DiscussionThe product of two-fold SET (6a) was always the main product of Table 1 in contrast to the results from reactions of A ·¯ with RX [8] -pivaloylaziridines [3]. This is in accord with the electron source 2a for the conversion 3a → 4a since 2a has a longer lifetime than aliphatic aziridino ketyls and can better compete with A ·¯. This SET from 2a to 3a may further profit from the reported [5] reversible dimerization of 2a if one ketyl of the separating pair undergoes ring opening before it diffuses away. The yields of 6a (and also of 6b in Table 2) may be a bit low in long term runs since 5a,b and analogous precursors can eliminate [5] the Nsubstituent as olefine (ethene from 5a) when Na + is the counter ion.or with Nhigher contributions are possible with Li. Product 21s (probably 3,3'-disubstituted tetrahydrobianthryl) may arise by hydrogen detachment from the first intermediate (29) of coupling with position 2 and dimerization of the formed 2-substituted A ·¯ (30). Coupling products may be fully aromatized or may be hydroxylated in one of the benzylic positions. With counter ion Li + a non-SET reaction of 1a with the dimer of A ·¯ is indicated by the isolation of 9-benzoyl-dihydroanthracene 15 and by 19% yield of 16a (aromatized 10a). Reaction of 3b with anthracene is indicated by 10,10'-disubstituted tetrahydrobianthryl 37.

Synthesis of Canthardin Sulfanilamides and Their Acid Anhydride Analogues via a Ring-Opening Reaction of Activated Aziridines and Their Associated Pharmacological Effects

“…It was through the regioselectivity ring-opening reaction, and the strong preference for normal-opening sulfonyl activation (R group was tosyl) that simply reflected the steric hindrance of a nucleophilic attack on the tertiary aziridine carbon in the inversional ground state. A single electron transfer (SET) mechanism was proposed to account for this unexpected behavior [35,36]. Therefore, we proposed that both normal and abnormal opening reactions of activated aziridines were slowed down compared to a reaction in the absence of the two methyl groups, the former clearly more so than the latter, and the white crystalline compounds 10i – k were obtained (Scheme 2).…”

Vinylphosphonium Salt-Mediated Reactions: A One-Pot Condensation Approach for the Highly cis-Selective Synthesis of N-Benzoylaziridines and the Green Synthesis of 1,4,2-Dioxazoles as Two Important Classes of Heterocyclic Compounds

“…Aziridines with structural fascination, pharmaceutical importance, and wide applications in synthetic chemistry have attracted particular attention from organic synthetic and medicinal chemistry communities. In particular, N -benzoylaziridines are an activated type of aziridines for the formation of ketyls and radical intermediates under the nucleophilic ring opening reactions . The development of synthetic methods for the synthesis of aziridines in the stereoselective manner is of relevance for the life-science industry. , Aziridines are known as key intermediates for many diverse products, such as bioactive aziridines and nonaziridine containing bioactive compounds as well as natural products .…”