The word umpolung was first introduced to Chemistry by Wittig in 1951,1 and later popularized by Seebach as “any process by which donor and acceptor reactivity of an atom are interchanged”.2 Indeed, the lone pairs present on a heteroatom X (N, O) are responsible for an alternating donor(d)/acceptor(a) reactivity in the carbon skeleton of the molecule (Figure 1); the inversion of this normal reactivity by a chemical modification (polarity reversal) is commonly defined as umpolung process.
Unconventional organocatalytic strategies by N-heterocyclic carbene (NHC) catalysis: umpolung reactivity and beyond
Alessandro Massi
2019
Abstract
The word umpolung was first introduced to Chemistry by Wittig in 1951,1 and later popularized by Seebach as “any process by which donor and acceptor reactivity of an atom are interchanged”.2 Indeed, the lone pairs present on a heteroatom X (N, O) are responsible for an alternating donor(d)/acceptor(a) reactivity in the carbon skeleton of the molecule (Figure 1); the inversion of this normal reactivity by a chemical modification (polarity reversal) is commonly defined as umpolung process.File in questo prodotto:
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