Functionalization At Will Of C₅-Symmetric Rim-Differentiated Pillar[5]Arenes And Solid State Structure Analysis

Since the introduction of pillararenes,especially pillar[5]arenes(P[5]s),to macrocyclic chemistry due to their facile synthesis and interesting symmetric properties,explorations towards various substituted patterns of P[5]s have become a hotspot for a decade.The P[5]s are usually obtained via the cyclization of symmetrically or asymmetrically substituted 1,4-dialkoxybenzene monomers under Lewis acid catalysis.However,C₅-symmetric rim-differentiated P[5]s,whose upper and lower rims are identical,were used to be considered difficult to synthesize since the regioisomers can be formed during the cyclization of unsymmetrical hydroquinone derivative.This situation has been significantly improved by the“preoriented”synthetic protocol in our previous report,while the purification steps of isomers are still non-trivial.Moreover,substituents on the rims of P[5]s are also limitations.With this regard,a more universal protocol towards large-scale synthesis and free functionalization of rim-differentiated P[5]molecules is highly desired.In this thesis,an alternative divergent synthetic procedure has been proposed to overcome limitations above,and these efficient routes made it possible to functionalize either rim of P[5]s at will.Firstly,a precursor penta-hydroxyl P[5],(OH)₅-P[5],was obtained in a gram scale synthesis with a much improved yield after simple isolation.Following alkylations and esterifications starting from(OH)₅-P[5]also showed fairly good results,where non-trivial purification can be spared and the issue that starting materials are incompatible with cyclization conditions of P[5]s is also solved.Furthermore,much more efficient reactions performed on P[5]scaffold have been explored and two productive approaches to functionalization of-OH moieties on(OH)₅-P[5]are employed,i.e.,sulfur(VI)fluoride exchange(Su FEx)reaction and Suzuki-Miyaura coupling.Finally,subsequent removal of the methyl groups on the other rim opens access to analogous functionalization schemes,thus allowing P[5]s to be functionalized fully at will on both sides.Extensive characterization of the resulting compounds was undertaken,including X-ray crystallography,to provide information on conformations in solid-state.