Gold(i)-catalyzed cycloisomerization of alcohol or amine tethered-vinylidenecyclopropanes providing access to morpholine, piperazine or oxazepane derivatives: a carbene versus non-carbene process
Org. Chem. Front., 2023,10, 1738-1745Jun-Sheng Wei,a Song Yang,a Yin Wei, b Sima Shamsaddinimotlagh,c Hossein Tavakol*c and Min Shi *a,b aKey Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, People’s Republic of China bState Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, University of Chinese Academy of Sciences, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China. E-mail: email@example.com cDepartment of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Iran. E-mail: firstname.lastname@example.org Abstract A gold(I)-catalyzed intramolecular cyclization of alcohol or amine tethered-vinylidenecyclopropanes via a carbene or non-carbene process was developed to afford functionalized morpholines, piperazines and oxazepanes in good yields with a broad scope and excellent functional group tolerance under mild conditions. The steric bulkiness or chain length can modulate the reaction pathway. Substrates with a less sterically hindered group located at the allene moiety afford morpholines or piperazines containing an alkylidenecyclopropane via the non-carbene process, while sterically bulky ones give morpholines or piperazines containing a cyclobutene unit through the carbene process. Moreover, extending the carbon chain length of vinylidenecyclopropane enables the formation of seven-membered oxazepane via the carbene process. The synthetic utility of this protocol was also highlighted by its gram-scale synthesis and various transformations of the cyclization products.