75859-92-6Relevant academic research and scientific papers
9-Demethyl-9-haloretinals by Wadsworth-Emmons coupling - Easy preparation of pure (all-E), (9Z) and (11Z) isomers
Wang, Yajie,Woo, Wei Sein,Van Der Hoef, Ineke,Lugtenburg, Johan
, p. 2166 - 2175 (2007/10/03)
5-(2′,6′,6′-Trimethyl-1′-cyclohexen-1′-yl) -4-penten-2-yn-1-al has been prepared in a one-pot process starting from β-ionone in almost quantitative yield. Using 1,4-nucleophilic addition reactions, the corresponding 9-Cl, 9-Br, 9-1 β-ionylideneacetaldehyde systems could be obtained in one step in quantitative yield as a mixture of (9Z) and (all-E) isomers. Even the corresponding fluoro derivative could be obtained in good yield as (9Z) and (all-E) isomers. In the case of a double bond having a halogen substituent, the IUPAC rules have the (E) nomenclature for a cis double bond and the (Z) for a trans double bond. Simple column chromatography gave the pure (9Z) and (all-E) form. Optimizing the Wadsworth-Emmons coupling gave the corresponding (all-E)- and (9Z)-retinonitriles in quantitative yield. Subsequent DIBAL-H reduction gave the corresponding retinals. For the preparation of the (UZ) isomers essential to vision, we found that Wadsworth-Emmons reactions with the diphenyl phosphonate group gave retinonitriles in quantitative yield, where the newly formed double bond is predominantly the (11Z) form (> 60%), together with the (9Z) isomer as minor component. The nitriles could be isolated in pure (9Z.11Z) and (9Z) forms by simple column chromatography. In the case of the (9Z,11Z)-9-demethyl-9-halo systems, a complication arose due to the unprecedented acid lability of these (9Z,11Z) aldehydes. By adjusting the DIBAL-H reduction workup procedure, these aldehydes are now available in pure form. We used this strategy to rationally synthesize (11Z)-retinal starting from β-cyclocitral as a first test for the generality of our new approach. β-Ionylideneacetaldehyde could be prepared in the (all-E) form in almost quantitative yield. Extending the conjugated chain of this molecule gave an almost quantitative yield of a mixture containing 80% (11Z)-retinal and 20% (all-E) as the minor component. Simple column chromatography gave pure (11Z)-retinal in 75% overall yield. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Stereoselective functionalization at C-9 of retinal: Synthesis of 9- trans-19-nor-9-haloretinal analogs
Shinada,Yoshihara
, p. 264 - 266 (2007/10/03)
Stereoselective functionalization at C-9 of retinal based on the use of the C4+X-unit is described. A sequential linkage of C4+X-units (X=Cl, Br, and I) with ylide 8 (C10) and phosphonate 12 (C5)selectively gave
