Sulfur analogues crown ethers

See, for a basic bibliography T. Shono in Supplement E The Chemistry of Ethers, Crown Ethers, Hydroxyl Groups and their Sulfur Analogues (Ed. S. Patai), Wiley, Ghichester,... 

For a review of pinacol rearrangements, see Bartok, M. Molnar, A. In Chemistry of Ethers, Crown Ethers, Hydroxyl Compounds and Their Sulfur Analogues, Patai, S., Ed. New York, 1980, Part 2, pp 722-733. 

Hetero analogues, in which oxygen is replaced either partially or completely by other heteroatoms, especially sulfur or nitrogen, are also known [179]. These hetero crown ethers are also called coronands or corands [180]. 

The selectivity of the formation of dimer [3,3]metacyclophanes lb and 8 versus trimer 18-membered macrocycles 2b and 9 which were perceived as crown ether analogues, was discussed by Vogtle in 1983 [6]. Both 1,3-bis(bromomethyl)benzene and 2,6-bis(bromomethyl)pyridine building blocks were used, with thioacetamide as the source of sulfur. Increasing the size of the counterion of the carbonate base raises the amount of trimers. Apparently, no higher oligomers were formed (Scheme 16.2). 

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