Reaction of (2-Nitro- and 2-Bromo-2-nitroethenyl)phosphonates with 1,3-Cyclohexadiene

Specific features of the reactions of bis(chloroethyl) 2-nitro- and 2-bromo-2-nitroethenylphosphonates with 1,3-cyclohexadiene were studied. It was found that the reaction with 2-nitroethenylphosphonate occurs stereoselectively and provides bis(2-chloroethyl) endo-(3-nitrobicyclo[2.2.2]oct-5-en-2-yl)phosphonate. 2-Bromo-2-nitroethenylphosphonate under the same conditions gives a mixture of the endo and exo isomers of the corresponding nitrobicyclooctenes. Enhanced tendency of adducts derived from gem-bromonitroethenyl-phosphonates for intramolecular transformations, such as dehydrohalogenation and aromatization, under the cycloaddition conditions was revealed.