51468-89-4Relevant academic research and scientific papers
Cross metathesis of β-carotene with electron-deficient dienes. A direct route to retinoids
Wojtkielewicz, Agnieszka,Maj, Jadwiga,Morzycki, Jacek W.
supporting information; experimental part, p. 4734 - 4737 (2011/03/18)
Cross metathesis (CM) reactions of β-carotene and alkenes occur regioselectively in the presence of the Hoveyda second generation catalyst. Scission of the C15-C15′ and C11-C12 bonds of β-carotene in all CM reactions predominates. The reaction with ethyl
The organoalkali route to vitamin A and β-carotene
Rauchschwalbe, Guenter,Zellner, Armin,Schlosser, Manfred
, p. 3903 - 3909 (2007/10/03)
The reductive cleavage of methyl vinyl-β-ionyl ether (1) or the deprotonation of 3,2′,6′,6′-tetramethyl-5-(1-cyclohexenyl)-1, 3-pentadiene (2) gives rise to an organometallic C15 species that combines selectively with a variety of electrophiles at the terminal chain position. Its reaction with aldehydes, however, is less clean. In particular, (E)-β-formyl-2-butenyl acetate gives the expected adduct 7a and, after dehydration, vitamin A acetate only in poor yield. The same is true for the analogous reaction with 2,7-dimethyl-2,4,6-octatriendial, which ultimately affords βcarotene. Vitamin A acetate can also be prepared, this time in moderate yield, by functionalization through consecutive deprotonation, borylation, oxidation and acetylation of a C20 pentaene hydrocarbon having the required skeleton. Both the C15 and the C20 organometallic key intermediates adopt spontaneously a zigzag-like outstretched conformation which, upon electrophilic trapping, directly and exclusively leads to the all-(E) configuration.
A novel, selective, and efficient route to carotenoids and related natural products via Zr-catalyzed carboalumination and Pd- and Zn-catalyzed cross coupling.
Zeng,Negishi
, p. 719 - 722 (2007/10/03)
[structure: see text]. A highly efficient and stereoselective protocol for the syntheses of symmetrical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl coupling has been developed and applied to the syntheses of beta- and gamma-carotene and vitamin A. gamma-Carotene of > or =99% isomeric purity was prepared in three linear steps (five steps overall) from beta-ionone, enyne 8, (E)-ICH=CHBr, and (E)-Me3SiC triple bond CCH=CHBr in 32% overall yield.
A novel regioselective synthesis of allylsilanes
Chan,Labrecque
, p. 1149 - 1152 (2007/10/02)
The anions derived from allyl sulfones were silylated in the α-position. Reductive desulfonylation gave the desired allylsilanes regioselectively
Retinoids and Carotenoids, V.- Synthesis of Modified Retinals
Bestmann, Hans Juergen,Ermann, Peter,Rueppel, Hartmann,Sperling, Walter
, p. 479 - 498 (2007/10/02)
The syntheses of 13-demethyl-13-ethyl-, 13-demethyl-13-propyl-, 13-demethyl-, 13-demethyl-14-methyl-, and 14-methylretinal are described.The UV spectra of some geometric isomers of these compounds are discussed.
Electro-organic Reactions. Part 16. The Preparative-scale Cathodic Hydrogenolysis and Coupling of Benzyl-, Allyl-, Cinnamyl-, and Polyenylphosphonium salts
Utley, James H. P.,Webber, Andrew
, p. 1154 - 1160 (2007/10/02)
An investigation of the cathodic reduction of benzyltriphenylphosphonium nitrate confirms that optimum yields of the product of coupling (bibenzyl) are formed at an aluminium cathode using high current densities and in dimethylformamide or hexamethylphosphoramide solution.The cathodic reduction of allylphosphonium salts gives mainly cleavage; e.g. α-farnesene (5) is obtained in 32percent yield from the corresponding farnesylphosphonium salt.Moderately efficient coupling (ca. 30percent) is observed for the electro-reduction of trans-cinnamyltriphenylphosphonium nitrate (6) and a C15 polyenylphosphonium salt (7).The products of coupling have been fully characterised; the relative proportions of positional isomers are apparently dictated by steric factors.
