168984-24-5Relevant articles and documents
Syntheses and Structures of 3,7-Substituted Barbaralanes
Quast, Helmut,Witzel, Martina,Peters, Eva-Maria,Peters, Karl,Schnering, Hans Georg von
, p. 725 - 738 (2007/10/02)
Short and efficient syntheses of barbaralanes 2e-h are reported, Meerwein's diketone 9 is converted into the bis(vinylsulphide) 10 by the action of 4-chlorothiophenol in the presence of titanium(IV) chloride and triethylamine.Oxidation of 10 with sodium perborate in acetic acid affords the bis(vinyl sulphone) 11 which is treated with potassium cyanide supported on aluminium oxide to yield the unsaturated dinitrile 8.Bromination of 8 with N-bromosuccinimide and subsequent reductive cyclisation of the resulting exo,exo dibromodinitrile 13 with the zinc-copper couple furnish 3,7-dicyanobarbaralane (2e) in 53percent overall yield based on 9. - Treatment of dinitrile 8 with hydrochloric acid in boiling methanol followed by hydrolysis of the intermediate Pinner salt yields the dimethyl dicarboxylate 14 which is brominated to afford the exo,exo dibromo diester 15.Reductive cyclisation of 15 gives rise to the formation of dimethyl 3,7 barbaralanedicarboxylate (2f) in 49percent overall yield based on 9. - Bicyclononane-3,7-dione (7) is converted into a mixture of the bis(vinyl sulphones) C2- and Cs-17 (1:1) as described for 9 --> 11.Bromination of the mixture yields a single exo,exo dibromo compound 18 which is cyclised by the zinc-copper couple to afford 3,7-bis(phenylsulphonyl)barbaralane (2g) in 56percent yield based on 7. - The known phenyl-2-oxaadamantol 21a is cleaved by the action of boron trifluoride and acetic anhydride to yield the bicyclononenone 22.The difluoroboron complex 23 is obtained under more rigorous conditions.Addition of phenylcerium(III) chloride to 22 followed by dehydration of the endo alcohol 24 yields the diphenyldiene 25.Bromination of 25 and subsequent reductive cyclisation of the exo,exo dibromodiphenyldiene 26 furnish 3,7-diphenylbarbaralane (2h) which is isolated by preparative reversed-phase chromatography in 50percent overall yield based on 7. - The configurations and conformations in the crystals are elucidated by X-ray diffraction analyses for the bicyclo nonane derivatives 7, 13, 15, 18, 22-24, and 26 and the barbaralanes 2e-g.In the solid state, 2e and f exist as pairs of rapidly rearranging nonequivalent valence tautomers while the atomic distances observed for 2g indicate the presence of a single nonrearranging valence tautomer. - Key Words: Barbaralanes / Tricyclo2,8>nona-3,6-dienes / Bicyclononane, derivatives of / Vinyl sulphones / Nitriles, α,β-unsaturated, from vinyl sulphones / Esters, α,β-unsaturated, from nitriles / 2-Oxaadamantanes, cleavage of / 2-Oxatricyclo5,7>decane, derivatives of / Phenylcerium(III) chloride reagent / Bromination with N-bromosuccinimide / Cyclisation by debromination with the zinc-copper couple / Reversed-phase liquid chromatography, preparative
