Azavinylidenephosphoranes: A Class of Cyclic Push-Pull Carbenes

作者：Lavigne Florie; El Kazzi Aimee; Escudie Yannick; Maerten Eddy^*; Kato Tsuyoshi; Saffon Merceron Nathalie; Branchadell Vicenc; Cossio Fernando P; Baceiredo Antoine

来源：Chemistry - A European Journal, 2014, 20(39): 12528-12536.

DOI：10.1002/chem.201402880

• carbene ligands
• carbenes
• density functional calculations
• synthetic methods
• ylides

The synthesis of a novel family of cyclic push-pull carbenes, namely, azavinylidene phosphoranes, is described. The methodology is based on a formal [3+2] cycloaddition between terminal alkynes and phosphine-imines followed by an oxidation/deprotonation step. Carbenes 6, obtained by simple deprotonation, exhibit typical transient carbene reactivity like the intramolecular C-H insertion reaction and a pronounced ambiphilic character exemplified by [2+1] cycloaddition with electron-poor methyl acrylate. Owing to the cyclic structure, carbenes 6 also exhibit an excellent coordination ability toward transition metals. Rh-I complex 10 was obtained in excellent yield and was fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. The corresponding Rh-I-carbonyl complex was also prepared; this indicates that carbenes 6 belong to the strongest sigma-donating ligands to date. DFT calculations confirmed the high sigma-donation ability of 6 and their classification as push-pull carbenes with a relatively small singlet-triplet energy gap of 23.2-24.3 kcalmol(-1).

• 出版日期2014-9-22