50688-77-2Relevant academic research and scientific papers
Aziridines. 76: Neglected aspects of anthracenide (anthracenidyl) chemistry - Reactions with two N-benzoylaziridines
Lin, Pen-Yuan,Weiss, Rainer,Werry, Juergen,Falkenstein, Reinhard,Stamm, Helmut
, p. 153 - 161 (2007/10/03)
Reaction of anthracenide A.- with N-benzoylaziridines 1a,b forms charged radicals 3a,b by single electron transfer and homolytic ring opening. Reactions follow that are known or expected as e.g. coupling with position 9 of A.- forming dihydroanthracene anions 9a,b that yield amidoethylated dihydroanthracenes 10a,b, or react with 1a,b giving finally 9,10-bis-amidoethylated dihydroanthracenes 11a,b. Results depend on experimental conditions and on the counter ions Na+ or Li+. Coupling is not regiospecific: contributions by positions 2 and 1 reach 29% or 4%, respectively, of total coupling with the primary radical 3a; much higher 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. Wiley-VCH Verlag GmbH, 2000.
Benzylic Fragmentation of Adducts formed from Anthracene Hydride and Benzoyl Compounds: A Non-concerted Process
Mall, Thomas,Stamm, Helmut
, p. 375 - 375 (2007/10/03)
A carbanion intermediate (4) of the title fragmentation can be trapped by an excess of N-benzoylaziridine 1 after a long (41 h) reaction time.
Reactions of Carbanions with two Sterically Demanding 1-Benzoylaziridines: SET, SN2, Carbonyl Attack.
Bellos, Konstantinos,Stamm, Helmut
, p. 269 - 273 (2007/10/02)
Reactions of 2-phenyl (1a) and 2-benzyl (1b) 1-benzoyl-2-butylaziridines with carbanions X-, AH-, and Fl- of xanthene, dihydroanthracene and fluorene always form N-(2-butylethyl)-benzamides carrying phenyl (9a) or benzyl (9b).This reductive ring opening indicates an SET mechanism with aziridino ketyls 6a,b as intermediates.Nucleophilic ring opening (SNs) is found only with the carbanion of the lowest reducing power: Fl- 5a,b (62percent, 14percent).These two mechanisms cleave different bonds, a finding without precedence in SN2/SET competitions.Carbonyl addition resulting in benzoyl transfer to xanthene, dihydroanthracene or fluorene is usually also observed.It is the main reaction with X- and 1a.The highest yields of 9a,b are obtained with AH- since a special inner-sphere SET is available.
Intermediate Substitution in the Formation of a Benzylic Anion by an Aromatic Radical Anion as Observed with 1-Benzoyl-2-phenylaziridine
Stamm, Helmut,Falkenstein, Reinhart
, p. 2227 - 2230 (2007/10/02)
The reaction of the title compound 1 with anthracene hydride AH(-) or anthracenide A(-*) leads to the formation of the benzylic anion 9 by fragmentation of the first generated substitution intermediate 7 or 8.In the reactions with AH(-) the carbanion 9 is completely trapped by protonation with dihydroanthracene AH2 yielding the reduction product 3 (N-benzoyl-phenethylamine).In reactions with A(-*) as well as with naphthalenide N(-*) the carbanion 9 either abstracts a proton from the solvent THF (yielding 3) or adds to the benzoyl group of unreacted 1 which finally results in β-benzamido-α-phenylpropiophenone (6).
Reductive Ring Opening of N-Benzoylaziridine by Anthracene Hydride (Anion of 9,10-Dihydroanthracene) via Base-Induced Fragmentation of the Intermediate Carbonyl Adduct
Stamm, Helmut,Mall, Thomas,Falkenstein, Reinhard,Werry, Juergen,Speth, Dieter
, p. 1603 - 1607 (2007/10/02)
As previously reported reaction of anthracene hydride (AH-) or of its oxa analogue xanthenyl anion (X-), with N-benzoylaziridines 1a,b can result in amidoethylation (2a,b and 3a,b) of the carboanion, in reductive opening (4a,b) of the aziridine ring, and in attack on the carbonyl group of 1a,b.We now show with 1a that both the rate of ring opening and the amount of reductive opening are significantly enhanced by an excess of AH-Li+ while the initially formed (90percent) carbonyl adduct 6a survives with a defict of AH-Li+.Both effects due to carbanion excess are absent with X-Li+ but are much stronger with AH-Na+.These results point to a rapid process that is triggered off by deprotonation at position 10 of the carbonyl adduct 6.A concerted or subsequent homolytic fragmentation is proposed to generate the ketyl 5 of 1, followed by homolytic ring opening of 5 to yield the radical 12, which is reduced to the carbanion 14.The latter forms 4 by capturing a proton from dihydroantracene.Inaccessibility of reductive ring opening for a trialkylacetyl-activated aziridine is demonstrated again (18).
Reactions with Aziridines, 45. - Arene Hydrides, 5 Reversibility of Carbonyl Attack on N-Benzoylaziridines Prior to Ring Opening by Carbanions. - Strong Influence of the Gegen Ion
Mall, Thomas,Stamm, Helmut
, p. 1349 - 1352 (2007/10/02)
A previous report had shown that anthracene hydride AH- or the xanthenyl anion X-, respectively, at first add to the carbonyl group of N-benzoylaziridines since high yields of benzoyl dihydroanthracene 3 or benzoyl xanthene 11 were obtained when in early stages the reaction was quenched with protons.The respective intermediate carbonyl adducts 2 and 10 had been considered to be precursors of products resulting from homolysis of the aziridine ring.It is now shown that quenching of the reaction between AH- or X- and N-benzoylaziridines 1a, b with methyl iodide or aroyl chlorides results in substantial yields of products derived from either AH- (or X-) or 1a,b.This indicates that 2 (or 10) are in equilibrium with AH- (or X-) and 1a, b.Study of the gegen ion influence with X- revealed that the equilibrium concentrations of 10-Na+ were much lower than those of 10-Li+ while simultaneously the ring opening of 1a was distinctly faster with X-Na+ than with X-Li+.This finding suggests that, contrary to the previous assumption, the equilibrium concentrations, of X- and 1a are responsibile for the (homolytic) ring opening.
Highly Regioselective Ring Cleavage of N-Acylaziridines by "Anthracene Hydride" (Anion of 9,10-Dihydroanthracene). Intermediacy of a Carbonyl Adduct. Influence of Nitrogen Inversion on the Ring Opening?
Stamm, Helmut,Sommer, Andreas,Woderer, Anton,Wiesert, Wolfgang,Mall, Thomas,Assithianakis, Petros
, p. 4946 - 4955 (2007/10/02)
Anthracene hydride AH- reacts with N-acylaziridines by reductive opening of the aziridine ring and/or amidoethylation of AH-.When the two aziridine carbons are differently substituted, in both reactions only that bond is broken which can form the more stable carbon radical quite in accord with the intermediacy of a radical anion (ketyl) 14 and with the known homolytic cleavage of 14 forming the radical 15.The extra electron in 14 is provided by AH- being oxidized to the radical AH., which can react with 15 either by radical combination or by hydrogen transfer.The reaction of AH- with N-aroylaziridines can be interrupted at the stage of the carbonyl adduct 5 as is shown by the isolation of the ketones 7a,b.So, 5 (R4 = aryl) is considered to be in equilibrium with the radical pair AH./14.The conversion of 5 into the final products progresses as expected from its structure apart from the observed retardation by a phenyl substituent in the aziridine ring (3a, 4a).This retardation is tentatively explained by a hypothesis assuming ring opening of 14 to occur in the transition state of nitrogen inversion.The anion X- of xanthene resembles AH- in its reactivity.Both carbanions react with N-sulfonylaziridines as expected from an SN2 mechanism.
