22679-53-4Relevant academic research and scientific papers
Donor-activated alkali metal dipyridylamides: Co-complexation reactions with zinc alkyls and reactivity studies with benzophenone
Armstrong, David R.,Brouillet, Etienne V.,Kennedy, Alan R.,Garden, Jennifer A.,Granitzka, Markus,Mulvey, Robert E.,Trivett, Joshua J.
, p. 14409 - 14423 (2015/01/08)
Previously it was reported that activation of tBu2Zn by [(TMEDA)Na(μ-dpa)]2led to tert-butylation of benzophenone at the challenging para-position, where the sodium amide functions as a metalloligand towards tBu2Zn manifested in crystalline [{(TMEDA)Na(dpa)}2ZntBu2] (TMEDA is N,N,N′,N′-tetramethylethylenediamine, dpa is 2,2′-dipyridylamide). Here we find altering the Lewis donor or alkali metal within the metalloligand dictates the reaction outcome, exhibiting a strong influence on alkylation yields and reaction selectivity. Varying the former led to the synthesis of three novel complexes, [(PMDETA)Na(dpa)]2, [(TMDAE)Na(dpa)]2, and [(H6-TREN)Na(dpa)], characterised through combined structural, spectroscopic and theoretical studies [where PMDETA is N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, TMDAE is N,N,N′,N′-tetramethyldiaminoethylether and H6-TREN is N′,N′-bis(2-aminoethyl)ethane-1,2-diamine]. Each new sodium amide can function as a metalloligand to generate a co-complex with tBu2Zn. Reacting these new co-complexes with benzophenone proved solvent dependent with yields in THF much lower than those in hexane. Most interestingly, sub-stoichiometric amounts of the metalloligands [(TMEDA)Na(dpa)]2and [(PMEDTA)Na(dpa)]2with 1 : 1, tBu2Zn-benzophenone mixtures produced good yields of the challenging 1,6-tert-butyl addition product in hexane (52% and 53% respectively). Although exchanging Na for Li gave similar reaction yields, the regioselectivity was significantly compromised; whereas the K system was completely unreactive. Replacing tBu2Zn with (Me3SiCH2)2Zn shut down the alkylation of benzophenone; in contrast, tBuLi generates only the reduction product, benzhydrol. Zincation of the parent amine dpa(H) generated the crystalline product [Zn(dpa)2], as structurally elucidated through X-ray crystallography and theoretical calculations. Although the reaction mechanism for the alkylation of benzophenone remains unclear, incorporation of the radical scavenger TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical) into the reaction system completely inhibits benzophenone alkylation.
Perfluoroalkanesulfonic acid catalyzed acylations of alkylbenzenes: Synthesis of alkylanthraquinones
Effenberger,Buckel,Maier,Schmider
, p. 1427 - 1430 (2007/10/03)
The acylation of alkylbenzenes 1 with benzoyl chloride 2 and catalytic amounts of perfluorobutanesulfonic acid affords the corresponding 2-, 3-, and 4-alkylbenzophenones 3 with unusually high amounts of ortho products. Surprisingly, even tert-butylbenzene reacts under these reaction conditions without any acid catalyzed dealkylation. The yield of benzoylation of p-xylene 4 with benzoic acid in the presence of 5 mol% C4F9SO3H to give 2,5-dimethylbenzophenone 5 could significantly be improved from 14% to 90% by continuous removal of water formed during the acylation. Also in the preparation of alkylanthraquinones 7 by reaction of alkylbenzenes with phthalic anhydride, water removal is the decisive factor to obtain satisfactory yields for the second acylation, allowing to cyclize 6 with catalytic amounts (10 mol%) of CF3SO3H in organic solvents to the corresponding alkylanthraquinones 7.
Ring tert-butylation of benzophenones and benzaldehyde with tert-butyllithium and thionyl chloride
Olah,Wu,Farooq
, p. 1179 - 1182 (2007/10/02)
One-flask ring tert-butylation of benzophenones and benzaldehyde with tert-butyllithium and thionyl chloride is reported. The scope of the reaction and the suggested mechanism are discussed.
RADIKALISCHE REAKTIONSWEGE BEI THERMISCH INDUZIERTEN UMSETZUNGEN VON ZIRCONOCENKOMPLEXEN
Erker, G.,Rosenfeldt, F.
, p. 1285 - 1292 (2007/10/02)
The formation of products 2, 3 and 4(a-l) from both the reaction of εta2-bezophenone zirconocene 1 with alkyl halides and the thermolysis of the α-(Cp2ZrCl)-substituted benzhydrylmethylether 9, the latter proceeding with anchimeric assistance of the metal, can be understood assuming a stepwise reaction path through radical intermediates.The proposed intermediate transition-metal benzophenone ketyl 12 exhibits a reaction pattern differing from analogous main-group-metal ketyls.
REVERSAL OF THE BENZOPHENONE REACTIVITY UPON η2 -COMPLEXATION TO BIS( η5 -CYCLOPENTADIENYL)ZIRCONIUM
Rosenfeldt, Frank,Erker, Gerhard
, p. 1637 - 1640 (2007/10/02)
Reversal of the carbonyl activity of benzophenone, serving as electron donor in single-electron transfer processes and acting as a proton acceptor through the 'carbonyl'carbon atom, is observed upon η2 -complexation to zirconocene.
