TANDEM INTER-[4-[3+2]CYCLOADDITIONS OF NITROALKENES - ASYMMETRIC-SYNTHESIS OF HIGHLY FUNCTIONALIZED AMINOCYCLOPENTANES USING THE BRIDGED MODE (BETA-TETHER) PROCESS(2]CYCLOADDITIONS INTRA)

An asymmetric, tandem inter [4 + 2]/intra [3 + 2] bridged mode (beta-t ether) cycloaddition of nitroalkenes has been developed. This new sequ ence involves the Lewis acid-promoted [4 + 2] cycloaddition of nitro o lefins with enantiopure 1-alkoxy-1,4-dienes. The resulting nitronates, bearing a C(5) tethered dipolarophile, undergo thermal, intramolecula r [3 + 2] cycloaddition to afford stable tricyclic nitroso acetals, wh ich can be subsequently reduced to provide interesting aminocyclopenta nes. Thus, in three steps, highly functionalized, enantiomerically enr iched aminocyclopentanes can be constructed with good yield and high e e. Additionally, the Lewis acid was found to impart a remarkable influ ence on the stereochemical outcome of the [4 + 2] cycloaddition.