Ketone transformation as a pathway to inherently chiral rigidified calix[4]arenes

Abstract

The preparation of inherently chiral rigidified calix[4]arenes with an intact cavity is a synthetic challenge due to the complicated synthesis of starting compounds. Here, we report on a novel strategy...

Upper Rim-Bridged Calix[4]arenes via Cyclization of meta Alkynyl Intermediates with Diphenyl Diselenide

“…The corresponding meta -substituted chloromercurio derivative 2 was obtained regioselectively in good yield (70%). A subsequent reaction with iodine provided the meta -iodo derivative 3 in 58% yield ( Scheme 3 ) [ 8 ]. The introduction of triple bond into the calixarene skeleton was carried out by Sonogashira coupling [ 11 , 12 ], which is well known for terminal alkynes.…”

“…The formation of an organomercury compound II then enabled the preparation of new types of calixarenes with a meta - meta bridged upper rim [ 7 ]. These compounds are not only interesting because of their highly increased rigidity (see e.g., III and IV ), but often also represent inherently chiral systems potentially suitable for the design of chiral receptors ( V – VII ) [ 8 , 9 ].…”

“…The bridging of two adjacent aromatic nuclei in the meta position leads to the formation of condensed tricyclic systems having a five-, six-, or seven-membered ring ( Scheme 1 ). While a number of systems having a five- or six-membered ring have been prepared, only three seven-membered systems ( V – VII ) have been described so far [ 8 , 9 ]. Thus, compounds of type V were obtained by cyclization of the corresponding meta -amides, and compounds VI and VII were obtained from ketone IV using a ring extension via Baeyer-Villiger or Beckmann rearrangements.…”

Directmetasubstitution of calix[4]arenes

“…The starting ketone-bridged calixarene 72 was “extended” into a two-atoms bridge via the corresponding rearrangement reactions (Baeyer–Villiger or Beckmann). 57 As shown in Fig. 30b, reaction of the ketone with m -chloroperbenzoic acid (MCPBA) in toluene resulted in the isolation of the lactone 100 in 58% yield.…”

Facile synthesis of a C4-symmetrical inherently chiral calix[4]arene

“…Functionalizing a calix [4]arene in the meta-position has been achieved in distinct ways such as intramolecular ring closing, [6][7][8][9] the p-bromodienone route 10 or directly using mercury(II) trifluoroacetate. 11,12 More commonly though this is achieved through the use of directing groups (DG) placed in the para-position (i.e. upper rim) of the calix [4]arene.…”