Spirodienones Calixarenes

Further oxidation of 43 leads to bis- or tris-spirodienone derivatives of calixarenes. They possess with the directionality of each spirodienone moiety an additional, independent stereogenic element. Thus, for a calix[4]arene derived bis(spirodienone) 45 six isomeric forms are possible, two meso forms and two pairs of C2-symmetric enantiomers, see Figure 8. The number of possible isomers increases with increasing of the number of rings in the macrocycle.92... 

Spirodienones are attractive intermediates for the preparation of calixarenes in which the intraanular hydroxy groups are partly replaced by hydrogen,93 amine 93 methyl,94 or halogen.95 The reaction with benzyne affords Diels-Alder adducts in high diastereofacial selectivity.92 No special use has been made of their chirality, however. 

The interesting stereochemical possibilities for the large-ring spherand-type calixarenes 16, which include compounds with >3 and symmetry, are discussed in ref. 14e. The intriguing stereochemistry of the calixarene spirodienones... 

For the preparation of multiply phosphorus bridged systems, we studied the pyrolytic behavior of calixarene dialkyl phosphate ester derivatives. These compounds are useful intermediates for the OH-depletion of the calixarenes [15, 16] and for the preparation of aminocalixarenes [17]. These esters can be prepared by treatment of the calixarenes with a dialkyl chlorophosphate in the presence of base [18]. In the case of 1, under mild conditions, the distal (i.e, 1,3-) bis(diethyl phosphate ester) derivative is obtained (2a) while under more drastic conditions (CH2Cl2/aq NaOH, phase transfer catalysis) the tetraphosphate 2b is formed [15a]. Calixarene mono diisopropyl phosphate ester and l,2-bis(diisopropyl phosphate ester) derivatives (2c and 2d) were prepared by mono- or dideprotonation by LDA of the monospirodienone derivative 3 followed by treatment with the corresponding dialkyl chlorophosphate [15e, 17b]. Aromatization of the spirodienone products was achieved by heating or by their treatment with HBr yielding the dialkylphos-phate esters derivatives 2c and 2d [15e, 17b]. 

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