The reaction of electrophiles with zwitterions generated from phosphines and activated carbon-carbon multiple bonds has emerged as an efficient synthetic strategy for the construction of carbon-carbon and carbon-heteroatom bonds. [1] Although the zwitterion formed by the addition of triphenylphosphine to dialkyl azodicarboxylate, commonly known as the Huisgen zwitterion (Scheme [1] ), [2] has found extensive use as the pivotal intermediate in the well-known ...
