The intramolecular Diels-Alder reaction of diene-tethered 1-alkenesulfinate esters

Snelgrove, Jennifer L.
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University of Guelph

This thesis deals with the intramolecular Diels-Alder reaction of diene-tethered 1-alkenesulfinate esters. Manipulations of the systems were done to investigate parameters which may affect the rate of cyclization and the stereochemical selectivity. These parameters include: the presence of β-substituents on the dienophile, the length of the tether between diene and dienophile, the identity of the atoms within the tether, the substituents on the tether and the identity of the diene. The effects of Lewis acids on stereoselectivity were also studied. In order for cyclization to occur, the electron-withdrawing power of the ester group on the dienophile is necessary. Lewis acid catalysis does not promote cyclization of the phenyl substituted system. The length of the tether connecting the diene and dienophile plays a significant role both in the rate of the cyclization and the selectivity. For the three atom tether at low temperatures only one isomer is formed. For the four atom tether, two isomers are formed even at low temperatures. The effect of replacing a methylene group within the tether with a dimethyl silyl group is surprising in that cyclization did not occur. The diene moiety was also changed from furan to thiophene in an attempt to observe the effect on the cycloaddition reaction. Despite using a system which cyclized readily in the case where the diene was furan, the thiophene sulfinate esters remained uncyclized despite trying Lewis acid catalysis. Attempts to oxidize the thiophene moiety to the mono- or 1,1-dioxide compounds, in order to facilitate cycloaddition, did not occur. Instead, the sulfinyl moiety was oxidized to a sulfonyl moiety. The preparation of cyclopentadiene alcohol analogues was also attempted without success.

Diels-Alder reaction, diene-tethered 1-alkenesulfinate esters, cyclization rate, stereochemical selectivity