81826-67-7Relevant articles and documents
Tebbe-like and Phosphonioalkylidene and -alkylidyne Complexes of Scandium
Baik, Mu-Hyun,Carroll, Patrick J.,Gau, Michael R.,Gu, Jun,Lee, Eunji,Mindiola, Daniel J.,Zatsepin, Pavel
, p. 10143 - 10152 (2020)
The bonding between scandium and carbon in a series of alkylidene- and alkylidyne-like moieties is compared. The Tebbe analogue complex (PNP)Sc(μ2-CHSiMe3)(μ2-CH3)[Al(CH3)(CH2SiMe3)] (2) (PNP- = N[2-PiPr2-4-methylphenyl]2) could be formed by adding AlMe3 to (PNP)Sc(CH2SiMe3)2 (1). The fluxional behavior of 2 is studied by a combination of 2D 13C-1H HMQC, HMBC, and other heteronuclear NMR spectroscopic experiments. The phosphonioalkylidene complex (PNP)Sc(CHPPh3)(CH3) (3) could be prepared from 2 by treatment with 2 equiv of the ylide H2CPPh3 or by methane elimination from (PNP)Sc(CH3)2 and 1 equiv of H2CPPh3. The reactivity of the alkylidene in 2 was further explored with N3Ad, which gave insertion at the Sc-C bond, yielding (PNP)Sc(CH3)[η2-N3AdCHSiMe3Al(CH3)(CH2SiMe3)] (4), while DMAP provided C-H activation across the alkylidene with loss of the Al-C bond to form (PNP)Sc(η2-NC5H3NMe2)(CH2SiMe3) (5). Utilizing the same approach that yielded 2, methane elimination in 3 could further be promoted with Al(CH3)3 to furnish the first example of a scandium phosphonioalkylidyne complex, (PNP)Sc(μ2-CPh3)(μ2-CH3)Al(CH3)2 (6). Experimental and theoretical studies were combined to compare the bonding in 2, 3, and 6, in order to understand the legitimacy of Sc-C multiple bond character.
Sterically crowded cyclohexanes - 9. Synthesis, conformation and dynamics of hexaspiro[2.0.4.0.2.0.4.0.2.0.4.0]tetracosane
Wulf, Karin,Klages, Ulrich,Rissom, Beate,Fitjer, Lutz
, p. 6011 - 6018 (1997)
The synthesis, conformation and dynamics of hexaspiro[2.0.4.0.2.0.4.0.2.0.4.0]tetracosane (3) are described. At room temperature in solution, 3 exists as 4 : 1 mixture of a rapidly interconverting twistboat conformation and a fixed chair conformation. The
An α-Cyclopropanation of Carbonyl Derivatives by Oxidative Umpolung
Bauer, Adriano,Di Mauro, Giovanni,Li, Jing,Maulide, Nuno
supporting information, p. 18208 - 18212 (2020/08/21)
The reactivity of iodine(III) reagents towards nucleophiles is often associated with umpolung and cationic mechanisms. Herein, we report a general process converting a range of ketone derivatives into α-cyclopropanated ketones by oxidative umpolung. Mechanistic investigation and careful characterization of side products revealed that the reaction follows an unexpected pathway and suggests the intermediacy of non-classical carbocations.
Intramolecular Acetyl Transfer to Olefins by Catalytic C?C Bond Activation of Unstrained Ketones
Rong, Zi-Qiang,Lim, Hee Nam,Dong, Guangbin
supporting information, p. 475 - 479 (2018/02/21)
A rhodium-catalyzed intramolecular acetyl-group transfer has been achieved through a “cut and sew” process. The challenge arises from the existence of different competitive pathways. Preliminary success has been achieved with unstrained enones that contain a biaryl linker. The use of an electron-rich N-heterocycilc carbene (NHC) ligand is effective to inhibit undesired β-hydrogen elimination. Various 9,10-dihydrophenanthrene derivatives can be prepared with excellent functional-group compatibility. The 13C-labelling study suggests that the reaction begins with cleavage of the unstrained C?C bond, followed by migratory insertion and reductive elimination.
