768-66-1Relevant articles and documents
Contrasting reactivity of mono- versus Bis-2,2,6,6-tetramethylpiperidide lithium aluminates towards polydentate lewis bases: Co-complexation versus deprotonation
Campbell, Ross,Crosbie, Elaine,Kennedy, Alan R.,Mulvey, Robert E.,Naismith, Rachael A.,Robertson, Stuart D.
, p. 1189 - 1201 (2013)
Two closely related lithium alkylaluminium amides LiAl(TMP)2iBu2 and LiAl(TMP)iBu3 (TMP: 2,2,6,6-tetramethylpiperidide) have been compared in their reactivity towards six polydentate Lewis bases containing either N or O donor atoms or a mixed N,O donor set. Seven of the twelve potential organometallic products of these reactions, which were carried out in hexane solution, have been crystallographically characterised. Three of these structures, [Li(-Me2NCH2CHCH2CH2CHO)(-TMP)Al(iBu)2], [Li(-Me2NCH2CH2OCH2)(-TMP)Al(iBu)2], and [Li(-Me2NCH2CH2OCHCH2NMe2)(-TMP)Al(iBu)2] reveal that the bis-amide LiAl(TMP)2iBu2 deprotonates (aluminates) the multifunctional Lewis base selectively at the carbon atom adjacent to oxygen with the anion generated captured by the residue of the base. In contrast, the mono-amide LiAl(TMP)iBu3 in general fails to deprotonate the Lewis bases but instead forms co-complexes with them as evidenced by the molecular structures of [Me2NCH2CHCH2CH2CH2O·Li(-iBu)(-TMP)Al(iBu)2], [Me2NCH2CH2OMe·Li(- iBu)(-TMP)Al(iBu)2], and [MeOCH2CH2OMe·Li(-iBu)(-TMP)Al(iBu)2]. Providing an exception to this pattern, the mono-amide reagent deprotonates chiral R,R,-N,N,N′,N′-tetramethylcyclohexanediamine to afford [Li(-CH2NMeC6H10NMe2)2Al(iBu)2], the final complex to be crystallographically characterised. All new products have been spectroscopically characterised through 1H, 7 Li, and 13C NMR studies. Reaction mixtures have also been quenched with D2O and analysed by 2D NMR spectroscopy to ascertain the full metallation versus co-complexation picture taking place in solution.
Visible-Light-Driven α-Allenylic C-O Bond Cleavage and Alkenyl C-S Formation: Metal-Free and Oxidant-Free Thiolation of Allenyl Phosphine Oxides
Zhang, Ling,Zhu, Jie,Ma, Jing,Wu, Lei,Zhang, Wei-Hua
, p. 6308 - 6311 (2017)
A visible-light photoredox cleavage of α-allenylic C-O bond and alkenyl C-S formation is disclosed for the first time. The thiolation of allenyl phosphine oxides with diaryl disulfides occurs smoothly in metal-free and mild conditions, affording novel S,P-bifunctionalized butadienes with moderate to excellent yields. Mechanistic studies explain the cleavage of a C(sp3)-O(Ar) bond in initiating a key alkenyl radical intermediate.
Reactions of a stable phosphinyl radical with stable aminoxyl radicals
Ishida, Shintaro,Hirakawa, Fumiya,Iwamoto, Takeaki
, p. 94 - 96 (2015)
Reaction of stable phosphinyl radical 1a with AZADO gave aminoxyphosphine 3 as the primary product by selective radical coupling at 140 °C. Compound 3 decomposed to phosphorane 4, silyl phosphinate 5, and aminophosphine 6 at room temperature. The molecular structures of 4-6 were determined by X-ray structural analysis. The homolytic N-O bond cleavage of 3 and the subsequent silyl migration of the resulting phosphinoyl radical 7 would be key steps in the reaction.
2,2,6,6-tetramethylpiperidinium chloride
Kaplan, Ruth W.,Turnbull, Mark M.
, p. 2049 - 2051 (1996)
Crystals of 2,2,6,6-tetramethylpiperidinium chloride, C9H20N+.Cl-, crystallized from dichloromethane solution. Hydrogen bonding between the piperidinium and chloride ions [d(N-H...Cl) = 3.16 and 3.30A] links the units into alternating chains running parallel to the crystallographic b axis.
A large-scale low-cost access to the lithium 2,2,6,6-tetramethylpiperidide precursor
Kampmann, Detlef,Stuhlmueller, Georg,Simon, Roger,Cottet, Fabrice,Leroux, Frederic,Schlosser, Manfred
, p. 1028 - 1029 (2005)
Wolff-Kishner-Huang reduction of the cheap 2,2,6,6-tetramethyl-4- piperidinone (2) provides the expensive 2,2,6,6-tetramethylpiperidine (1), the precursor to lithium 2,2,6,6-tetramethylpiperidide, in high yield. As specified in the detailed protocol, the reaction can be conveniently carried out on a >10 mol laboratory scale. Georg Thieme Verlag Stuttgart.
Photochemical Synthesis of 1,4-Dicarbonyl Bifluorene Compounds via Oxidative Radical Coupling Using TEMPO as the Oxygen Atom Donor
Xu, Jincheng,Ding, Aishun,Zhang, Yanbin,Guo, Hao
, p. 3656 - 3666 (2021)
A visible-light-induced metal-free synthesis of 1,4-dicarbonyl compounds from alkyne-containing aryl iodides via photochemical C-I bond cleavage, intramolecular cyclization, oxidation, and intermolecular radical coupling sequence is reported. TEMPO was employed as the oxygen atom donor in this transformation. This protocol provided a new strategy for the synthesis of 1,4-dicarbonyl bifluorene compounds.
Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
K?nig, Burkhard,Wang, Hua,Wang, Shun
supporting information, p. 1653 - 1665 (2021/06/17)
Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
supporting information, p. 1611 - 1615 (2021/03/03)
An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
Copper-Catalyzed Cascade N-Dealkylation/N-Methyl Oxidation of Aromatic Amines by Using TEMPO and Oxygen as Oxidants
Li, Dianjun,Wang, Shihaozhi,Yang, Jiale,Yang, Jinhui
supporting information, p. 6768 - 6772 (2021/12/31)
A novel tandem N-dealkylation and N-methyl aerobic oxidation of tertiary aromatic amines to N-arylformamides using copper and TEMPO has been developed. This methodology suggested an alternative synthetic route from N-methylarylamines to N-arylformamides.
Catalytic CO2 hydrosilylation with [Mn(CO)5Br] under mild reaction conditions
García, Juventino J.,González, Tania
, (2021/06/07)
Carbon dioxide hydrosilylation with earth-abundant transition-metal catalysts is an attractive alternative for the design of greener and cost-effective synthetic strategies. Herein, simple [Mn(CO)5Br] is an efficient precatalyst in the hydrosilylation of carbon dioxide with Et3SiH under mild reaction conditions. Using THF as a solvent, triethylsilylformate Et3SiCH(O)O was obtained in 67% yield after 1 h at 50 °C and 4 bar of CO2 pressure. The selectivity of the reaction was tuned by changing the solvent to a mixture of THF and toluene producing bis(triethylsilyl)acetal (Et3SiO)2CH2 in 86% yield. The CO2 hydrosilylation was also effective at room temperature and atmospheric pressure using either THF or the mixture THF/toluene as the solvent resulting in high Et3SiH conversion (92%–99%) but with a decrease in the selectivity. Radical trapping experiments indicated the participation of radical species in the catalytic mechanism. To the best of our knowledge, this is the first report on CO2 hydrosilylation catalyzed by transition-metal radical intermediates.
