Chemoselective oxidation of phenoxathiin-based thiacalix[4]arene and the stereoselective alkylation of productsElectronic supplementary information (ESI) available: Spectral characterization of compounds, temperature dependent NMR spectra of 4 and 5, NOE experiments with 4, and X-ray structures of 6c and 7d. CCDC 1844676, 1844677, 1846763, 1846764 and 1846766. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8nj04690e

Phenoxathiin-based thiacalix[4]arene, accessible via acid-catalysed rearrangement of the starting spirodienone derivative, was subjected to the oxidation of sulfur bridging groups. Using an excess of the oxidation agent, systems bearing four sulfonyl groups or three sulfonyl and one sulfoxide group are available in high yields, depending on the reaction conditions. Although four different conformations can be obtained, the alkylation with various alkylating agents led stereoselectively to derivatives being immobilized in the partial cone conformation. The structure of products was assigned using a combination of NMR techniques and single crystal X-ray analysis. All compounds represent inherently chiral building blocks potentially useful in the design of novel thiacalixarene-based receptors. Phenoxathiin-based thiacalix[4]arene was subjected to exhaustive oxidation. Depending on the reaction conditions, the macrocyclic systems bearing four sulfonyl groups or three sulfonyl and one sulfoxide group are available in high yields.