Efficient synthesis of calix[4]resorcinol rccc diastereoisomers using high amount of trifluoroacetic acid in the chloroform medium

The use of excess of trifluoroacetic acid in chloroform (1 : 1, v/v) in a one-pot acid-catalyzed cyclocondensation of functionalized benzaldehydes with 2-methylresorcinol significantly improves the yield of calix[4]resorcinol rccc diastereoisomers compared to rctt ones. The fraction and yield of the rccc isomers sometimes approach 100% along with shortening the reaction time. The structure of new rccc diastereoisomer of chlorine-containing calix[4]resorcinol has been established by single crystal X-ray diffraction.