From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• ]nonadienes (bisdioxines) 4. When arylamines are used as the nucleophiles under neutral conditions, decarboxylation occurs during the formation of bisdioxines 8. However, when water or alcohols are added to 3 under acidic conditions, bisdioxine-carboxylic acids and esters 10 and 11 are obtained. Acid

• bisdioxine and tetraoxaadamantane formation are discussed. Keywords: bisdioxines; dipivaloylketene; tetraoxaadamantanes; transannular cyclization; Introduction The tetraoxaadamantane ring system is relatively unknown and no functional group derivatives had been reported prior to our work. The first methyl

• allowed the preparation of numerous derivatives of the unique 2,6,9-trioxabicyclo[3.3.1]nonadiene (bisdioxine) system 8–13, namely the monoamides 8, the diacid 11, the diacid dichloride 12, and the esters 9, 10 and 13 [18][19] (Scheme 3). The mechanism of formation of these derivatives is summarized in

Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

• Gert Kollenz,
• Ralf Smounig,
• Ferdinand Belaj,
• David Kvaskoff and
• Curt Wentrup

Beilstein J. Org. Chem. 2015, 11, 1–8, doi:10.3762/bjoc.11.1

• Abstract The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray

• unique 2,6,9-trioxabicyclo[3.3.1]nonadiene (“bisdioxine”) system, including the diacid, the diacid dichloride 2 [2] and the diethyl ester 3 [3] are readily synthesized from the stable dimer of dipivaloylketene. DFT calculations at the B3LYP/6-31G** level predict that molecules of this type can exist only

• bridge. This ascertains that the functional groups with their attachments are oriented essentially parallel, i.e., away from the concave bisdioxine backbone. Furthermore, the intramolecular hydrogen bonds depicted in Figure 3 and Figure 4 ascertain that the two pendant hexylamino chains in 4 are held in

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• functionalized with nitroaryl and arylamino groups were synthesized from the bisdioxine diacid dichloride 1,3,5,7-tetra-tert-butyl-2,6,9-trioxabicyclo[3.3.1]nona-3,7-diene-4,8-dicarbonyl dichloride (3). Keywords: bisdioxine; macrocyclic amines; macrocyclic nitro compounds; tetraoxaadamantane; Introduction The

• concave, axially chiral [1], bridged bisdioxine diacid dichloride 3 is obtained by acid hydrolysis and subsequent chlorination of the surprisingly stable α-oxoketene 2, itself obtained by dimerization of dipivaloylketene (1) (Scheme 1) [2][3]. The concave structure of 3 and its derivatives together with

• the sterically hindering tert-butyl groups make it an interesting spacer group, and it thus has been applied successfully in syntheses of several macrocyclic polyether and polymethyleneoxy rings containing one, two or three bisdioxine units, e.g., 4 and 5 (Scheme 1) [4][5]. Capping of a calix[6]arene