1237706-60-3Relevant academic research and scientific papers
The ambivalent chemistry of a free anionic N-heterocyclic carbene decorated with a malonate backbone: The plus of a negative charge
Cesar, Vincent,Labat, Stephane,Miqueu, Karinne,Sotiropoulos, Jean-Marc,Brousses, Remy,Lugan, Noel,Lavigne, Guy
supporting information, p. 17113 - 17124 (2014/01/06)
The anionic heterocycle [maloNHC]- , ([1] -), is the archetype of a growing family of N-heterocyclic carbenes incorporating an anionic backbone; here, a malonate group. A comprehensive experimental exploration of its chemistry as a free entity (in the form of its lithium salt [1] Li) is presented, and rationalized using DFT calculations at the B3LYP/6-31+G* level of theory. For the sake of comparison, similar computations were performed on other representative carbene types. Reactions of [1]?Li with a broad series of electrophilic reagents were used to ascertain its intrinsic nature as a nucleophilic carbene. Unexpectedly, [1]?Li was also seen to react with the nucleophilic tert-butylisocyanide, to give an anionic ketenimine, which could be subsequently derivatized, either into an imine by protonation of the ketenimine moiety, or into a neutral ketenimine by alkylation of the intracyclic malonate moiety. Further experiments on the electrophilic behavior of [1]?Li revealed its unexpected reactivity toward p-chlorobenzaldehyde, resulting in a formal Ci￡H activation and the first structurally characterized keto-tautomer of the Breslow intermediate. Finally, [1]?Li remarkably activates polar Ei￡H bonds, including N-H bonds from ammonia and amines, Sii￡H bonds, and Bi￡H bonds. Importantly, DFT calculations indicate the importance of counterion effects. In particular, the key to the observed reactivity appears to be a modulation of energy levels associated with a dynamic variability of the Lii￡O distance between the remote malonate group and the counterion. An adaptive carbene: The lithium salt of the free anionic maloNHC is prone to react with a variety of organic substrates, including both classical electrophilic organic reagents and nucleophilic ones, like tert-butylisocyanide. It is also seen to react with 4-chlorobenzaldehyde through a formal C-H activation and to activate N-H, Si-H, and B-H bonds (see scheme; Mes=mesityl). The clue to such an ambivalent behavior is a dynamic variation of orbital energy levels under the control of the counterion.
Ammonia N-H activation by a N,N′-diamidocarbene
Hudnall, Todd W.,Moerdyk, Jonathan P.,Bielawski, Christopher W.
supporting information; experimental part, p. 4288 - 4290 (2010/08/06)
The synthesis and characterization of N,N′-dimesityl-4,6-diketo-5,5- dimethylpyrimidin-2-ylidene is reported; this crystalline N,N′- diamidocarbene was found to split ammonia and engage in other reactions not exhibited by typical N-heterocyclic carbenes.
