DIASTEREOSELECTIVE DIELS-ALDER CYCLOADDITIONS WITH CHIRAL 1-(ALKYLSULFINYL)-2-NITROALKENES

Several chiral 2-nitro-1-sulfinylalkenes were prepared and examined for their utility as dienophiles for asymmetric [4 + 2] cycloaddition. Trisubstituted dienophiles 3-6 undergo diastereoselective cycloaddition with cyclopentadiene in the presence of Lewis acids. Even the tetrasubstituted chiral sulfinyl dienophiles 1 and 2 could be coerced into undergoing [4 + 2] cycloaddition to afford the cycloadducts in high yield without concomitant elimination if the reaction was conducted under high pressure. Generally, the Z-sulfinyl dienophiles 1-4 showed higher diastereo- and endo/exo-selectivity than;the E-dienophiles 5 and 6.