The inside alkoxy effect revisited - The importance of electrostatic interactions in the stereoselective 1,3-dipolar cycloadditions of nitrones to chiral allyl ethers: An experimental and force field approach

The 1,3-dipolar cycloaddition of formaldehyde N-benzylnitrone with beta'-alkoxy- and gamma-alkoxy-alpha, beta-unsaturated esters was investigated. The stereochemical outcome of these reactions was nicely rationalized on the basis of an interpretation of the inside alkoxy theory emphasizing the electrostatic interactions in the reaction TS. The force field approach previously developed for evaluating the stereoselection in nitrile oxide cycloadditions to chiral alkenes was successfully extended to nitrones' reactions.