Ring Closing Enyne Metathesis Of Imidazole Derivatives And Subsequent Diels-Alder Reaction

Abstract

The work presented in this thesis describes the development of new synthetic routes to elaborate simple imidazole derivatives into complex imidazole molecules by the application of different sequential transformations. The first transformation considered is the ring closing enyne metathesis (RCEYM) of imidazoles. To carry out this reaction various allyl and propargyl derivatives of imidazole have been synthesized. These enyne substrates have been varied by changing the positions on the imidazole, as well as changing the protecting groups. All substrates contain trimethysilyl-protected propargyl derivative as the "yne" moiety. After the successful preparation of different enyne substrates, they were subjected to the metathesis reaction using Grubbs' second generation catalyst. The majority of enyne substrates participated RCEYM smoothly to produce the expected diene derivatives in moderate yields.

The next transformation employed was the Diels-Alder (DA) reaction on the diene derivatives obtained from the RCEYM reaction. For this transformation, first N-phenylmaleimide has been used as the dienophile with the diene substrates and all these cycloaddition reactions provided the expected cycloadduct in good yields. Finally, different dienophiles have been used for the DA reaction using one of the diene produced by RCEYM of dimethylaminosulfamoyl (DMAS) protected enyne substrate. These DA reactions also resulted in the expected cycloadducts in good yields. Unexpected results have been observed from two of the substrates while attempting the metathesis reaction.