syn-π-Face- and endo-selective, inverse electron-demand Diels–Alder reactions of 3,4-di-tert-butylthiophene 1-oxide with electron-rich dienophiles

Diels–Alder reactions of 3,4-di-tert-butylthiophene 1-oxide with oxygen (or sulfur)-substituted dienophiles and with simple alkenic dienophiles, which are classified as an inverse electron-demand Diels–Alder reaction on the basis of DFT calculations, took place exclusively at the syn-π-face of the diene with respect to the SO bond to provide the corresponding adducts in high yields.