1,1 ’,3,3 -Tetraphenyl-2,2 -biimidazolidinylidene

Reaction of phenols bearing strong electron-withdrawing substituents such as dichlorophenols and nitrophenols with 1,1, 3,3 -tetraphenyl-2,2 -biimidazolidinylidene results in poor yields. Oxidation of the electron-rich olefin by nitro compounds is also possible. 

Finally, an additional synthesis of recent times (1971) comes from Lappert and his group (48). They treated an electron-rich olefinic system, such as 1, l, 3,3 -tetraphenyl-2,2 -biimidazolidinylidene, with a suitable complex compound. In this manner, they attained cleavage of the C=C double bond and attachment of the carbene fragment to the metal ... 

A. H-[2,4-Bis(, 7>-diphenylimidazolidin-2-yl)-5-hydroxy-phenyl] acetamide. A 500-mL, 3-necked flask equipped with nitrogen inlet, mechanical stirrer, reflux condenser, and thermometer is charged with 88.8 g (0.2 mol) of l,l, 3,3 -tetraphenyl-2,2 -biimidazolidinylidene (Note 1) and 30.2 g (0.2 mol) of 3-acetami-dophenol (Note 2). The system is flushed with and maintained under nitrogen, and 100 mL of chlorobenzene (Note 3) is added. The suspension is stirred at 100°C for 6 hr (Note 4). 2-Propanol (250 mL) is added to the hot mixture, which is then allowed to cool to room temperature. A pale yellow solid precipitates which is filtered and washed with 200 mL of 2-propanol. Drying in vacuum affords 84.6-93.2 g (71-78%) of TV- [2,4-bis( 1,3-diphenylimi-dazolidin-2-yl)-5-hydroxyphenyl]acetamide, mp 254-256°C (Note 5). 

The reaction of l,l, 3,3 -tetraphenyl-2,2 -biimidazolidinylidene with phenols illustrated in this procedure is a general method for the preparation of phenolaldehydes.2 Table I gives the aldehydes that have been prepared by conditions similar to those described here. 

---