83027-21-8Relevant academic research and scientific papers
Steric factors in the single-electron transfer carbolithiation and transannular reduction of 6,12-diphenyldibenzo[b,f][1,5]diazocine by organolithium reagents
Eisch, John J.,Yu, Kun,Rheingold, Arnold L.
, p. 818 - 832 (2014/03/21)
The puckered tricyclic heterocycle 6,12-diphenyldibenzo-[b,f][1,5] diazocine, a novel probe for revealing single-electron transfer (SET) reactions, is here employed as a model substrate for investigating the carbolithiation of imines and the stereochemistry, the regiochemistry, and the electronic nature (polar or SET) of such R-Li additions. The chemical behavior of the following organolithium reagents (mainly in THF) toward the diazocine was studied: benzyl-, methyl-, phenyl-, n-butyl-, and phenylethynyllithiums, as well as the reactive allylmagnesium chloride and the typical tert-butylmagnesium chloride. The only reagent that failed to carbometalate or to reduce the diazocine transannularly was phenylethynyllithium. The tert-butyl Grignard reagent could not carbometalate but did reduce the diazocine with photocatalysis. The other five organometallics yielded both carbometalation of the diazocine and, upon hydrolysis, transannular SET reduction to 4b,9b-diphenyl-4b,5,9b,10- tetrahydroindolo[3,2-b]indole ( indoloindole ) in varying pro- portions. Three types of carbometalation products were observed in such hydrolyzed reactions: (1) exo-1,2-addition to a C=N bond by C6H 5CH2Li, H2C=CHCH2MgCl, and CH 3Li, as established by spectral and XRD data; (2) 1,4-addition to the ortho-phenyl carbon Co=C-C=N linkage by phenyllithium with the subsequent elimination of LiH; and (3) 1,4-addition, as in type 2, by n-butyllithium but without the elimination of LiH. The foregoing modes of reactivity, the concomitant formation of the telltale SET reduction product, indoloindole , and the failure of PhC≡CLi to react at all with the diazocine are marshaled to support the conclusion that the organometallics reacting with the diazocine, by carbometalation and by transannular reduction, do so by SET processes and not by straightforward nucleophilic attack. The relative stabilities of sp3-, sp2-, and sp-hybridized carbon radicals possibly involved were assessed in concluding that PhC≡CLi is incapable of reacting through any SET pathway.
6,12-Diphenyldibenzo[b,f][1,5]diazocine as an electron-capture agent: Efficient mechanistic probe for SET processes and reagent for the oxidative dimerization of benzylic organometallics
Eisch, John J.,Yu, Kun,Rheingold, Arnold L.
experimental part, p. 3165 - 3171 (2012/06/30)
In the present study, 6,12-diphenyldibenzo[b,f][1,5]diazocine, which X-ray diffraction measurements have now shown to possess a tub-shaped, eight-membered central ring, has been treated with sodium or lithium metal at 25 °C in THF, in an attempt to form the planar, Hueckel-aromatic dianion by the addition of two electrons to the central diazocine. Hydrolysis of such an aromatic dianion should have led to the isomeric 5,12- or 5,6-dihydro derivative of the original diazocine. In actuality, the only product obtained quantitatively upon hydrolytic workup was the interesting quadricyclic transannular reduction product, 4b,9b-diphenyl-4b,5,9b,10-tetrahydroindolo[3,2-b]indole, whose 3D structure has now been confirmed by X-ray crystallography and 13C NMR spectroscopy. Preferential SET transannular reduction of the diazocine to yield the quadricyclic indolo[3,2-b]indole dianion, rather than the planar, Hueckel-aromatic anion, is ascribed to the transannular electronic stabilization operative in the tub-shaped diazocine radical-anion. The quantitative generation of the indolo[3,2-b]indole dianion can be employed for the oxidative dimerization of the organic groups in benzylic lithium reagents. Thus treating one equivalent of the diazocine with two equivalents of benzyllithium, benzhydryllithium, or trityllithium yields quantitatively bibenzyl, 1,1,2,2-tetraphenylethane, or (4-benzhydrylphenyl)triphenylmethane, respectively. This oxidative dimerization is potentially of practical preparative scope, since the hydrolysis byproduct, the indolo[3,2-b]indole, is conveniently reconverted into the starting diazocine reagent by oxidation with chromium trioxide in acetic acid. The formation of the indolo[3,2-b]indole as a byproduct in the carbometalation of the diazocine by various RLi and Grignard reagents offers a clue as to the SET mechanism of carbometalation. Copyright
Electrochemical Reduction of Di-Schiff Bases. Synthesis of Piperazines, Indoloindoles, Diazepines, and Diazocines
Koch, Russell W.,Dessy, Raymond E.
, p. 4452 - 4459 (2007/10/02)
The electrochemical reduction of a series of di-Schiff bases had led to examples where products representing reduction, cyclization, and transannular cyclization are found.Useful synthetic pathways for piperazines, indoloindoles, diazepines, and diazocines are described.
