Umpolung

Umpolung or polarity inversion in organic chemistry is the chemical modification of a functional group with the aim of the reversal of polarity of that group. Quotes The carbonyl group is electrophilic at the carbon atom and hence is susceptible to attack by nucleophilic reagents. Thus, the carbonyl group reacts as a formyl cation or as an acyl cation. A reversal of the positive polarity of the carbonyl group so it acts as a formyl or acyl anion would be synthetically very attractive. To achieve this, the carbonyl group is converted to a derivative whose carbon atom has the negative polarity. After its reaction with an electrophilic reagent, the carbonyl is regenerated. Reversal of polarity of a carbonyl group has been explored and systematized by Seebach. George S. Zweifel and Michael H. Nantz Modern Organic Synthesis (2006), Ch. 1. Synthetic Design Umpolung in a synthesis usually requires extra steps. Thus, one should strive to take maximum advantage of the functionality already present in a molecule. George S. Zweifel and Michael H. Nantz Modern Organic Synthesis (2006), Ch. 1. Synthetic Design The most utilized Umpolung strategy is based on formyl and acyl anion equivalents derived from 2-lithio- 1,3-dithiane species. George S. Zweifel and Michael H. Nantz Modern Organic Synthesis (2006), Ch. 1. Synthetic Design External links Category:Organic reactions