Design, synthesis, and applications of stereospecific 1,3-diene carbonyls

The strategy toward the synthesis of various 1,3-dienals or 1,3-dienones is disclosed between diazo compounds and furans, which features metal-free, additive-free, broad functional group tolerance, and readily accessible starting materials. Notably, this strategy is applicable in both intramolecular and intermolecular protocols. Mechanistic studies suggested that the reactions undergo a cyclopropanation/rearrangement sequence. With an E / E -1,3-dienal, corresponding N -tosylhydrazones were readily prepared and subjected to phenylboronic acid to form a double bond migration product and indoles to construct a five-member ring via [3 + 2] annulation reaction.