Di(tert‐butyl)diazomethan: Thermische Zersetzung und Einelektronen‐Redox‐Reaktionen

Abstract

Di(tevt-buty1)diazomethane: Thermal Decomposition and One-Electron Redox ReactionsDi(tert-buty1)diazomethane is a potential precursor for the still unknown, presumably sterically overcrowded tetrakis(tert-buty1)ethane and, therefore, re-investigated. Its (HeI) photoelectron spectrum exhibits a low first vertical ionization energy of only 7.45 eV. Based on the ionization pattern, both the thermal decomposition above 600 K under nearly unimolecular conditions as well as the N, elimination at the surface of contacts, [NiJC],, [Rh4(C0),2/Si02]oo, [Rh,/SiO2lW, and [Ag2C0,], are analyzed in a flow-system. Heterogeneously catalyzed, N, is split off already at room temperature, but in contrast to results for sterically less shielded diazo compounds, no dimer is formed, and only mixtures of known di(tert-buty1)carbene-isomenzation products are isolated. Cyclic voltammetry at 233 K using a glassy carbon electrode proves a reversible oxidation followed by N, elimination at higher temperatures and an irreversible reduction. On chemical oxidation, however, no paramagnetic species can be detected, whereas chemical reduction at a potassium metal mirror in a THF solution containing (2.2.2)cryptand, yields the radical anion characterized by ESR spectroscopy. Without a cation-chelating ligand, the radical anion of a hitherto unknown dimer, ((CH;),C),C=N-N=N-N=C(C (CH,),), G, is generated, which dissociates at higher temperature, forming ((CH,);C),=N, e, This one-electron reduction product of di(tert-buty1)diazomethane can also be detected after quickly warming up a solution containing presumably the radical anion of the triphenylphosphane adduct ((CH,),C),C=N-N-PPh, e. In one of these reduction reactions, a N, elimination is observed.1. Einleitung. -Diazoalkane, erstmalig vor nunmehr 109 Jahren von 2%. Curtius synthetisiert, zeigen vielfaltige Reaktivitat [6]. Es lag daher nahe, ausgehend von dem in dreistufiger Synthese zuganglichen Bis(tert-buty1)diazomethan [7] (vgl. Exper. Ted) folgende weitere Moglichkeiten zur Herstellung des noch immer ~nbekannten;)~)'), als sterisch iiberfiillt vorausgesagten6) Tetra(tert-buty1)ethens zu untersuchen (Schema 1 ).Bekannt ist, dass die heterogen-katalysierte N,-Abspaltung aus gasformigem 2-Diazopropan an Raney-Ni etwa gleiche Anteile Propen und Tetramethylethen liefert [ 121

Tetra-tert-butylethylene, fantasy, fake, or reality?

“…But carbene 5 has an alternative unimolecular reaction channel, which is kinetically favoured by both concentration and orientation effects. This is the intramolecular C-H insertion into one of the six methyl groups, to give 1,1-dimethyl-2-tert-butylcyclopropane (9). This pathway is observed experimentally and calculations give an explanation for this finding.…”

“…Recently Ephritikine et al found also some reduction of the keto to a methylene group, when di-tert-butylketone was treated with TiCl 4 /Li [7c]; a carbenoid species was deduced as intermediate by the authors. They have been several attempts to dimerize di-tert-butylcarbene (5), but neither low temperature photolysis of di-tert-butyldiazomethane [8], nor thermal decomposition of di-tert-butyldiazomethane yielding carbene 5 on metal surfaces any dimerization products were obtained [9]. It should be mentioned that several "tied-back" derivatives of alkene 1 such as anti-fenchylidenefenchane (6), have been successfully prepared [2, 10].…”

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

“…The ratio of the produced hydrocarbons 5 -7 varied with the nature of the catalyst, and chemisorbed di(tert-butyl)carbene was assumed responsible. Both radical cation and radical anion of 4 appear to lose N 2 rapidly [15]. We are not aware that reactions of 4 with Brønsted acids have been studied.…”

“…Bock et al studied the conversions of 4 in a flow system above 600 K at 10 À2 mbar on the surface of metal catalysts [15]. The ratio of the produced hydrocarbons 5 -7 varied with the nature of the catalyst, and chemisorbed di(tert-butyl)carbene was assumed responsible.…”

Structural and Spectroscopic Properties of Aryl Substituted Aminoboranes as Model Compounds and Synthons for B/C/N Materials and New Fluorescent Systems

“…The structural and spectroscopic data of the heteroaromatic compounds 1 and 2, both depicted in Figure 3, which can be considered as examples of an arylated, BN-substituted ethylene, were hitherto unknown. They were prepared according to standard procedures described in Equation (1) and characterized by 1 H, 13 C, and 11 B NMR spectroscopy, UV/Vis spectroscopy, and single crystal XRD. (1) Compound 1 is a completely phenylated derivative of aminoborane H 2 B=NH 2 , which exists as a monomer only under extreme conditions [3,9,10].…”