Stable Carbenes—Illusion or Reality?

Some ten years ago a graduate student in chemistry would have failed sadly in his masters examination, had he contended that carbenes could be stored in bottles at room temperature. But precisely this is possible with the compounds 1 and 2, which were recently described by Arduengo et al. and by Bertrand et al. Compound 1 melts only at 240°C, owing to electronic and stereochemical effects. The carbene 2 not only shows carbene reactivity but also reactivity characteristic of phosphaalkynes. R = adamantyl, R′ = iPr2N.