Regio- and Diastereoselective Nitroso Diels-Alder Cycloaddition Reactions of 3-dienyl-2-azetidinones with Nitrosoarenes

The regioselective nitroso Diels-Alder (NDA) reactions of trans 3-butadienyl-2-azetidinones with nitrosoarenes leading to the synthesis of novel and diastereomerically pure 3-(3,6-dihydro-2H-1, 2-oxazin-6-yl) azetidin-2-one derivatives and cis 3-butadienyl-2-azetidinones resulting in a diastereoselective mixture of regioisomers are investigated. The observed regioselective behavior is supported by computational model, Ab initio [HF/6-31G (d)] and density functional theory [B3LYP/6-31G (d)] calculations. Additionally, the effect of solvation (in dichloromethane) in these reactions was also investigated in order to mimic the experimental solvent conditions.