Steric and conformational control of the regioselectivities in the ene reaction with trisubstituted cycloalkenes: Comparison of the enophiles singletoxygen, triazolinedione, and nitrosoarene

[GRAPHICS] The nitrosoarene ene reaction with the cycloalkenes 1-3 and E-4 proceeds in high twix regioselectivity to afford the hydroxylamine ene products 1a-4a (twix) and 1b-4b (twin, except far E-4 twirl, Steric interactions in the en ophile attack are responsible for the skew trajectory of the nitrosoarene e nophile, For Z-1-methylcyclooctene (Z-4), twin abstraction dominates, cause d by conformational constraints (transannular interactions) in the hydrgoge n-atom abstraction, The balance between these steric and conformational fac tors dictates the regioselectivity in the ene reaction.