Assisted substitution reactions

Microwave-Assisted Substitution Reactions via Addition Elimination 3.2.1... 

Scheme 24 Microwave-assisted substitution reaction from a factor Xa inhibitor development program...

You ve already met the most important ones—sulfides, esters, carboxylates. Ethers and amines (you will see some of these shortly) can also assist substitution reactions through neighbouring group participation. The important thing that they have in common is an electron-rich heteroatom with a lone pair that can be used to form the cyclic intermediate. Sulfides are rather better than ethers—this sulfide reacts with water much faster than rc-PrCl but the ether reacts with acetic acid four times more slowly than rc-PrOSC Ar. 

Scheme 5-6. Copper-assisted substitution reactions of bromoferrocene, Fc-Br.

Kinetic studies37,152 have established that the rate laws for the racemization and the nucleophile-assisted substitution reactions are very similar ... 

Scheme 4.27 TMG(1) assisted substitution reaction for the practical preparation of ertapenem...

This is a primary bromoalkane with two beta branches in the presence of a cyanide ion, a good nucleophile. Dimethyl sulfoxide (DMSO), a polar aprotic solvent, is a particularly good solvent in which to carry out nucleophile-assisted substitution reactions because of its good ability to solvate cations (in this case, Na" ) and its poor ability to solvate anions (in this case, CN ). From this analysis, we predict that this reaction occurs by an Sj 2 mechanism. 

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