Proximal O,O′-capped calix[4]arenes with a disiloxane bridge as highly efficient synthetic intermediates for 1,2-dialkylation at the lower rim

Chemistry of Thiacalixarenes

“…These were used as bidentate Lewis acid catalysts in the Mukaiyama-aldol reaction. [34] A similar strategy has been used [35] for the synthesis of proximally dialkylated thiacalixarenes 35 (Scheme 4). Treatment of 2 with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane provides the proximally disiloxane-bridged compound 33 in 92 % yield.…”

Functionalization reactions of calixarenes

“…It is noteworthy that compounds of the type of 96 and 97 are inherently chiral due to the presence of two differently substituted adjacent aromatic rings. 104 All of these reactions proceeded smoothly and with excellent yields ions. 109 The direct alkylation of calixarene 92 with substituted benzaldehydes 110a,b has been reported.…”

“…The treatment of 89 with the organohalides MeI, BrCH 2 COOEt or PhCH 2 Br yielded 1,2-alt 93 a-c which upon desilylation by TBAF gave O,O'-dialkylated 1,2-alt calixarenes 94a-c. 104 However, it was found that the treatment of 89 with methyl iodide under changed conditions may give monomethylated product 95. The reaction of the remaining hydroxyl group of 95 with benzyl bromide completed the alkylation yielding 1,2-alt 96 which upon deprotection with TBAF afforded 1,2-alt 97.…”

Monocyanomethylated thiacalix[4]arenes: synthesis and lower rim modification

“…The lower apparent differences in the OH acidities 6 of the thiacalix [4]arenes as compared to the classical ones prevents the regio-and stereoselective partial O-alkylation and acylation of thiacalix [4]arenes . As a result, the relatively easy formation of tetralkylated thiacalix [4] 12 have been proposed to overcome the problems encountered in basemediated alkylations. In this paper we report the first examples of the selective monoalkylation of thiacalix [4]arene and some chemical transformation of the monocyanomethylated thiacalix [4]arenes.…”