Enantiospecific Synthesis and Chiroptical Properties of Bicyclic Enones

Abstract

The enantiospecific synthesis of several bicyclic enones starting from enantiomerically pure (+)‐(1S,5S)‐bicyclo[3.3.1]nonane‐2,6‐dione (1) was accomplished. The target enones 7–9 were obtained in high yield and purity by using a catalytic amount of benzeneselenic anhydride. (+)‐(1S,5R)‐bicyclo[3.3.1]nonane‐2,3,6‐trione was obtained from diketone 1 by α‐hydroxylation involving the use of iodine under basic conditions. The reaction included a ring closure/reopening sequence via oxatricyclo[4.3.1.03,8]decane‐10‐one. It was shown that the latter triketone exists in enone/enol form. Chiroptical properties of the enantiomerically pure compounds were studied, and the sign of the Cotton effect was related to the absolute configuration of the enones. The positive Cotton effect in the bisignate CD curve is accounted for by the nonplanarity of the chromophore in enones (1S,5R)‐4 and (1S,5S)‐8. The circular dichroism spectra provided evidence for interchromophoric interaction in dichromophoric bis(enone) 9. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

4,8‐Disubstituted Bicyclo[3.3.1]nona‐2,6‐dienes as Chiral Ligands for Rh‐Catalyzed Asymmetric 1,4‐Addition Reactions

“…Synthesis of chiral dienes commenced with the preparation of (+)‐( 1R , 5R )‐bicyclo[3.3.1]nona‐3,7‐diene‐2,6‐dione ( 2 )16 by sulfinylation17 of enantiomerically pure 2,6‐dione 1 with methyl phenylsulfinate in the presence of sodium hydride, followed by thermal elimination (Scheme ). Luche reduction18 (NaBH 4 /CeCl 3 ) of the obtained bis(enone) 2 in methanol afforded diol 3 as a mixture of endo,endo ‐ and endo,exo ‐diastereomers in ca.…”

Enantioselective Ring Opening of meso‐Epoxides with Silicon Tetrachloride Catalyzed by Pyridine N‐Oxides Fused with the Bicyclo[3.3.1]nonane Framework

“…The latter was obtained from 2,6-dione 4 in a three-step procedure, [25] which includes monothioketalization and subsequent Raney Ni reduction, followed by Jones oxidation of the resulting alcohol (Scheme 1). The latter was obtained from 2,6-dione 4 in a three-step procedure, [25] which includes monothioketalization and subsequent Raney Ni reduction, followed by Jones oxidation of the resulting alcohol (Scheme 1).…”

“…Enantiomerically pure (1S,5S)-bicyclo[3.3.1]nonane-2,6-dione (4) [19] and (1S,5S)-bicyclo[3.3.1]nonan-2-one (9) [25] were prepared by following the reported procedures. Chalcones 7a-7d (except 7c) are known compounds and were obtained through a modified literature procedure [40] in 80-97 % yields.…”

Synthesis, Molecular Structure, and Chiroptical Properties of Dibenzylidene Derivatives of Bicyclo[3.3.1]nonane and Brexane

“…The latter was obtained from 2,6-dione 1 in a three-step procedure, 29 including monothioketalization and subsequent Raney Ni reduction, followed by Jones oxidation of the resulting alcohol (Scheme 1).…”

“…Enantiomerically pure bicyclo [3.3.1]nonane-2,6-dione 1 and bicyclo[3.3.1]nonan-2-one 3 were prepared following the reported procedures. 28,29 (3E,7E)-3,7-dibenzylidenebicyclo[3.3.1]nonane-2,6-dione 2 30,31 . Procedure A: By following a slightly modified literature procedure, 30 a solution of KOH (168 mg, 3 mmol) in methanol (3 mL) was added dropwise to a boiling solution of racemic 2,6-dione 1 (457 mg, 3 mmol) and benzaldehyde (670 μL, 6.6 mmol) in methanol (3 mL).…”