The acyclic nitroso-Diels–Alder reaction proceeds exceedingly smoothly with TIPS derivatives, but rather slowly with TMS ethers, a fact that is of great mechanistic interest. 6- Methyl-2-nitrosopyridine (1 equiv) was treated with a 1: 1 mixture of two silyloxydienes (1.4 equiv each) in competitive experiments with and without the use of a copper catalyst [Eq.(1)]. The OTIPS diene was clearly shown to be far more reactive than the OTMS or OTBS ...
