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Structure of the allyl group. In organic chemistry, an allyl group is a substituent with the structural formula −CH 2 −HC=CH 2.It consists of a methylene bridge (−CH 2 −) attached to a vinyl group (−CH=CH 2).
In redox-transmetalation/ligand exchange the ligands of two metal complexes switch places with each other, bonding with the other metal center. The R ligand can be an alkyl, aryl, alkynyl, or allyl group and the X ligand can be a halogen, pseudo-halogen, alkyl, or aryl group. The reaction can proceed by two possible intermediate steps.
Vinyl cations were first proposed in 1944 as a reactive intermediate for the acid-catalyzed hydrolysis of alkoxyacetylenes to give alkyl acetate. [5] In the first step of their facile hydration reaction, which was the rate limiting step, a vinyl cation reactive intermediate was proposed; the positive charge was believed to formally lie on a ...
While initial research in the field focused on the coupling of alkyl groups, most future work involved the much more synthetically useful coupling of vinyl, alkenyl, aryl, and allyl organostannanes to halides. Due to these organotin reagent's stability to air and their ease of synthesis, the Stille reaction became common in organic synthesis.
Often such agostic interactions involve alkyl or aryl groups that are held close to the metal center through an additional σ-bond. [2] [3] Short interactions between hydrocarbon substituents and coordinatively unsaturated metal complexes have been noted since the 1960s.
Despite broad success with aryl and vinyl couplings, the use of alkyl halides is less general due to several complicating factors. Having no π-electrons, alkyl halides require different oxidative addition mechanisms than aryl or vinyl groups, and these processes are currently poorly understood. [9]
Vinyl and aryl Grignard reagents couple with primary alkyl halides in the presence of a catalytic amount of a copper(I) halide salt. The use of Li 2 CuCl 4 rather than simple copper(I) halide salts (CuX) improves yields of these coupling reactions. [15] (5)
A phenyl group is the simplest aryl group, here bonded to an "R" group. In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. [1] "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used as a placeholder for the ...