Carbanions displacement

A better possibility PI1CH2C)- adds to C60 Then autoxidation of a benzylic C-H bond occurs to give the hydroperoxide. Then the C60 carbanion displaces OH- from the hydroperoxide to give the product. 

Reaction of the mesylated lignin prepared in step 1 (Fig. 1) with the polystyryl carbanion (living polystyrene) from step 2 (Fig. 2). The carbanion displaces the mesylate groups on the lignin in a nucleophilic displacement reaction with the formation of the polystyrene-lignin graft copolymer (Fig. 3). 

Arylannelation of 1,3-dienes.2 In the presence of catalytic amounts of Pd(OAc)2, BU4NCI (1 equiv.), and a base such as Na2C03 or NaOAc (5 equiv.), an aryl iodide reacts with a 1,3-diene (excess) to afford substituted carbocycles. The overall process is believed to involve an intramolecular carbanion displacement of a 7t-ally[palladium intermediate. 

Thus polystyryl carbanions and polyacrylonitrile carbanions prepared by anionic polymerization were reacted with cellulose acetate or tosylated cellulose acetate in tetrahydrofuran under homogenous reaction conditions. The carbanions displaced the acetate groups or the tosylate groups in a S v2-type nucleophilic displacement reaction to give CA-g-PS and CA-g-PAN. Mild hydrolysis to remove the acetate/tosylate groups furnishes the pure cellulose-g-polystyrene (Figure 3). 

A number of carbanion displacement reactions are discussed in Chapter... 

Almost all alkylations carried out in basic media are carbanion displacement reactions. The following syntheses are examples. 

The halogenation process may be regarded as a carbanion displacement reaction on a halogen molecule in equilibrium with the hypo-halite 18... 

The methods developed for the synthesis of 1-alkynylphosphonates use synthetic concepts such as charge affinity inversion and positive halogen abstraction. Four main reaction categories allow the preparation of 1-alkynylphosphonates the apparent Michaelis-Arbuzov and Michaelis-Becker reactions, the propargyl phosphite-allenylphosphonate rearrangement, carbanionic displacements at quinquevalent phosphorus centers SNPfV), and conversions of vinyl- to alkynylphosphonates by addition-elimination reactions. 1-Alkynylphosphonates possess remarkable potential, and cycloaddition reactions appear to offer very attractive synthetic procedures. ... 

Groups other than a carbonyl can stabilize a carbanion. Meyers described the preparation of a-lithio derivatives of dihydro-1,3-oxazines (282) and 2-oxazolines (284) and their use in alkylation and condensation reactions via a-lithio derivatives such as (283). Meyers treated the commercially available 285 with n-butyl-lithium to form the a-lithio derivative (286), stabilized by chelation with the nitrogen. When iodomethane was added, a carbanion displacement reaction occurred to give 287.The imine unit in 287 was reduced with borohydride (sec. 4.4.A) to give amine 288, and hydrolysis produced the aldehyde (in this case propanal). 

The product of reaction of sodium hydroxide with p-nitrobenzyldimethyl-sulfonium tosylate in water at 60°C is a mixture of cis- and trani-4,4 -dinitro-stilbenes in 99% yield Again, the reaction is first order in each reactant. After a short reaction time in DO /DaO the benzylic protons were at least 97% exchanged for deuterium . This eliminates the carbanion displacement mechanism. The over-all sulfur isotope effect is 1.0066 0.0008, lower... 

Another carbanion stabilized by two carbonyl groups is formed. This carbanion displaces intramole cularly a chloride atom. 

The resulting carbanion displaces intramolecularly the bromine atom, producing a very strained cyclopropanone. 

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