Synthesis of Calix[6]thiophenes and Calix[6]furans

Lee, Gon‐Ann; Shih, Yi‐Fan; Lin, Hung‐Chun; Wang, Wen-Chieh; Chan, H. W. S.; Lee, Hsin‐Yi; Lee, Chih‐Yi

doi:10.1002/slct.202002226

Cited by 2 publications

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Hydrogenation of Calix[4]pyrrole: From the Formation to the Synthesis of Calix[4]pyrrolidine

Journot¹,

Neier

Gualandi

2021

Eur J Org Chem

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In memory of François Diederich, a dear friend and an inspiring colleague Calix[4]pyrroles can be obtained from the efficient preprogrammed condensation between acetone and pyrrole. This reaction forms the attractive macrocycle resembling in its constitution, but not in its oxidation state, to the porphyrin structure, prominently present in the vital "pigments of life". Calix[2]pyrrolidine[2]pyrrole and calix[4]pyrrolidine, the partially and totally reduced version of the macrocycle, became accessible through the hydrogenation of calix[4]pyrrole, but only under strenuous reaction conditions. The only known hydrogenation, which could give clues for improving the process, was the reduction of the calix[4]furan. To shed light on the process, mixed calix[n]furan[4-n]pyrroles were prepared, and their hydrogenation was studied. After a laborious optimization process, the best conditions were discovered improving the yield of the hydrogenation process from the level of a formation to the level of a complete conversion. The calix [4]pyrrolidine is now accessible in two high yielding synthetic steps. The efforts to understand and to optimize the factors involved in the hydrogenation process of this perazamacrocycle are here reviewed.

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