Use of Steric Hindrance and a Metallacyclobutene Resting State to Develop Robust and Kinetically Characterizable Zirconium-Based Imine Metathesis Catalysts

Kinetic Resolutions by Means of Cycloaddition Reactions

“…The highly reactive metalϪnitrogen double bond underwent addition with a wide variety of unsaturated organic molecules, including alkynes, [59] imines [60] and certain alkenes. [61] More recently, the authors have extended this investigation to systems capable of undergoing highly enantioselective reactions, such as the chiral imido complex 67, possessing the C 2 -symmetric EBTHI [bis(tetrahydroindenyl)ethane] ligand.…”

Dynamic imine chemistry in metal–organic polyhedra

“…Similar to imine formation, transimination also proceeds to the formation of tetrahedral intermediate (aminal) that subsequently decomposes to give a new imine and amine. [10][11][12][13][14][15][16] Recently, Stefano and Ciaccia critically discussed the mechanism operating in imine chemistry in organic solvents and unambiguously explained the mechanistic aspects of hydrolysis, transimination, and metathesis reactions. 3 Transimination may be homotransimination (both amines are aliphatic or aromatic) and heterotransimination (one is aliphatic and other is aromatic) and influence by Brönsted and Lewis acids, [4][5][6] for instance, Sc III triflate salts catalyse the exchange reactions between sterically hindered imines, derived from 9anthracenecarboxaldehyde, and several amines in chloroform.…”

Synthesis of Chiral, Enantiopure Zirconocene Imido Complexes: Highly Selective Kinetic Resolution and Stereoinversion of Allenes, and Evidence for a Stepwise Cycloaddition/Retrocycloaddition Reaction Mechanism

“…Our observations a) demonstrate the operation of a general and highly selective kinetic resolution, b) provide the first example of a reaction that can be used to selectively invert the absolute configuration of one (symmetrically or unsymmetrically 1,3-disubstituted) allene enantiomer within a racemic mixture, and c) provide strong mechanistic evidence for the stepwise nature of an organometallic cycloaddition reaction.Previous work in our laboratories has shown that zirconocene ± imido complexes undergo cycloaddition reactions with a wide range of unsaturated organic molecules including alkynes, [10] imines, [11] and certain alkenes. [1] The analogous reactivity of metal ± heteroatom multiple bonds, such as those in metal ± imido complexes, has been known for a much shorter time and has only relatively recently been utilized in synthetic applications.…”