Frustrated Lewis Pair (FLP)‐Like (Cyclo)Addition of Small Organic Molecules to a Stable Azomethine Ylide

Abstract Azomethine ylides are 1,3‐dipolar zwitterions typically used for constructing N‐heterocycles by 3+2‐cycloaddition reactions. We report here a pyridyl‐tethered isolable azomethine ylide ( AY ) that activates a series of H−E bonds (E═B, Si, Al, O) in FLP‐like fashion. The reactions are probed mechanistically by DFT calculations and each case appears to be distinct from others. While the HBpin activation is stepwise, the same of PhSiH 3 is concerted. The AlH 3 activation is also stepwise but takes place across the 1,5‐(C + /N − ) dipole. The hydrolysis of AY fits better with a “relay” mechanism with two H 2 O molecules working in tandem. The B−B bond of B 2 pin 2 is also cleaved but in an intriguingly different way, by delivering both the Bpin moieties at the carbenic site. Though the challenging H 2 activation fails, a transfer hydrogenation of AY by NH 3 •BH 3 is readily achieved. AY also undergoes cycloadditions with various dipolarophiles including unactivated alkene and alkynes. In this regard, AY makes an interesting distinction between CO 2 and CS 2 by staying inert to the former but easily cycloadding the latter. DFT analysis justifies this dichotomy by showing the cycloaddition of CO 2 as thermodynamically disfavored.