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47142-GB1
Pd(0)-Catalyzed [3+2] Cycloadditions Involving Novel Epoxide and Aziridine Containing Trimethylenemethane Precursors

Kevin L. Jantzi, Valparaiso University

During the last year, four students and I have worked on this project.  We have synthesized a large amount of compound 1, an important intermediate in the synthesis of our desired epoxide (3) and aziridine (4) precursors for the Pd(0)-catalyzed Trimethylenemethane (TMM) cycloaddition reactions.  We have also scaled up the Swern oxidation and can routinely do the reaction on a 10 mmol scale with good results and yields.  We have also made some initial studies related to the formation of compound 4 which indicate that it may be possible to use intermediate aldehyde 2 as a precursor to both compounds 3 and 4. 

            Based on a large number of reactions using various conditions, it is quite clear that compound 3 does not undergo the Pd-catalyzed reactions shown below.  Apparently, the epoxide does not open to form the intermediate π-allyl palladium complex, even though similar model systems by Trost have been shown to undergo epoxide opening.  We have been able to repeat these two reactions using known precursors from the literature, so it is clear that our technique and reagents are fine.  It may be that the large TMS group of compound 3 is blocking the approach of the palladium catalyst.  In any event, we plan to use a variety of Lewis acids (e.g., TMSOAc, BF₃·OEt₂, TMSCl) to promote opening of the epoxide.   We also plan to use a more electron rich palladium catalyst which may better promote ring opening. 

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