Functionalised Cookson's Diketones in Chlorosulfonic Acid: Towards Polysubstituted D₃-Trishomocubanes

Abstract

A number of Cookson's diketone ( Cs-trishomocubane-8,11-dione) derivatives were synthesised and introduced into the reaction with chlorosulfonic acid to give previously unknown polysubstituted D3-trishomocubanes (pentacyclo[6.3.0.02,6.03,10.05,9]undecanes) – chiral analogues of the parent cubanes. In the case of 1,9-dibromo- Cs-trishomocubane-8,11-dione, the reaction proceeded with conservation of both carbonyl groups selectively affording 3-bromo-6-chloro- D3-trishomocubane-4,7-dione whose distinct substitution pattern was confirmed by means of X-ray structural analysis.

Reactions of Cookson’s diketone with potassium halides in the polyphosphoric acid medium

“…However, tetracyclo[6.3.0.0. 4,11 .0 5,9 ]undecane-2,7-dione 8 was formed in this case too, albeit in smaller amount (30 % in the crude mixture as judged by GC/MS). The main product (70 % in the crude mixture) was 3-bromotetracyclo[6.3.0.0 4,11 .0 5,9 ]undecane-2,7-dione 9.…”

“…4,11 .0 5,9 ]undecane-2,7-dione 8 was formed in this case too, albeit in smaller amount (30 % in the crude mixture as judged by GC/MS). The main product (70 % in the crude mixture) was 3-bromotetracyclo[6.3.0.0 4,11 .0 5,9 ]undecane-2,7-dione 9. Since tetracyclic bromodiketone 9 had quite similar NMRspectra compared to the possible product with the D 3 -trishomocubane skeleton and the same molar mass, its structure was confirmed by the X-Ray single crystal structure analysis (Fig.…”

“…Its physicochemical constants were in agreement with the literature data for tetracyclo[6.3.0.0. 4,11 .0 5,9 ]undecane-2,7-dione 8 [9]. Obviously, in this case reduction took place instead of the expected rearrangement to the D 3 -trishomocubane system (Scheme 2).…”

“…The rearrangement of C S -trishomocubane (pentacyclo[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane) derivatives (1, Fig. 1) under acidic conditions is the most general approach for the synthesis of D 3 -trishomocubanes (2, Fig.…”

“…So far, the only satisfactory reagent for the rearrangement of ketones is chlorosulfonic acid [2 -4], which has rather low tolerance of functional groups and is not too easy to handle. Moreover, in case of substituted Cookson's diketones such rearrangement often proceeds non-selectively and affords hardly separable mixtures of polysubstituted D 3 -trishomocubanes [5].…”