FROM UNSTABLE DIAZOALKENES TO STABLE PSEUDO-DIAZOALKENES - CREATING USEFUL SYNTHONS FROM REACTIVE INTERMEDIATES

Diazoalkenes are highly unstable compounds, which have only been obser ved below 11K! They have mostly been used as alkylidene carbene precur sors and more specifically in the conversion of carbonyl compounds int o the homologous alkynes. In contrast, pseudo-diazoalkenes such as dia zomethylenephosphoranes and boratadiazoalkenes are stable at room temp erature. They can be used as 1,3-dipoles as well as ylides, allowing t he synthesis of a variety of heterocycles, the isolation of new carben es and nitrile-imines, and can be considered as naked carbon synthetic equivalents.