Electrophilic diamination of alkenes by using FeCl₃-PPh₃ complex as the catalyst

The FeCl₃-PPh₃ complex was found to effectively catalyze the electrophilic diamination reaction of electron-deficient alkenes. Improvements on yields and stereoselectivity have been achieved for both α,β-unsaturated carboxylic esters and ketones. Under the new catalytic system, α,β-unsaturated carboxylic esters were found to be superior to their ketone counterparts, which is opposite to the previous (C₃F₇CO₂)₂Rh}₂ -catalyzed diamination. The reaction employs readily available N,N-dichloro-p-toluenesulfonamide (TsNCl₂) and acetonitrile as the nitrogen sources and is very easy to perform at room temperature without the special protection of inert gases. The resulting diamino products belong to imidazolidine analogue and can further strengthen the importance of the new reaction. Modest to good yields (52-84%) and high regio- and stereoselectivity have been achieved for 10 examples.