strategy based on the heteroatom‐free tri‐atom donor to synthesize 3,6‐dihydro‐2H‐pyrans has been developed. In this method, 2‐arylpropylene served as tri‐atom donor to contribute three carbon atoms, the heteroatom was provided by aldehyde, and DMSO served as one carbon donor and solvent. This annulation reaction gave 3,6‐dihydro‐2H‐pyrans in moderate to good yields. Based on the control experiments, a
Cationic iron(III) porphyrin was found to be an efficient catalyst for the highly chemoselective hetero-Diels Alder-type reaction of aldehydes with 1,3-dienes. The catalyzed process did not require the use of electron-deficient aldehydes such as glyoxylic acid derivatives or activated electron-rich 1,3-dienes such as Danishefslcy's diene and Rawal's diene. The high functional group tolerance and robustness of the catalyst were demonstrated. Further, the potential utility of the catalyst was demonstrated by performing the cycloaddition in the presence of water and by carrying out cycloaddition of an unactivated ketone such as cyclohexanone with a diene.