Regio- and Stereo-chemical Study of the Diels–Alder Reaction between (E)-3,4-Dimethoxy-β-nitrostyrene and 1-(Trimethylsilyloxy)buta-1,3-diene

The Diels–Alder addition of 1 to 2 under thermal and Lewis acid-catalysed conditions gives the regiostereoisomers 3, the structures of which are deduced by NMR analysis; only the thermal reaction is of any preparative value and semi-empirical calculations are developed in an attempt to discover the dominant factors influencing the ortho–meta orientation.