Abstract:370ChemInform Abstract Addition of the Grignard reagent (II) to carbonyl compounds gives alcohols which have a 1,3-butadienyl group. When copper complexes, prepared from (II) and CuI are used, conjugate addition products are obtained. In all cases the initial E/Z-ratio of the chloride (I) is found to be retained with little change in the products. The methodology can be extended to the synthesis of the pheromone (IV).
“…Starting from known phenylbutadienyl ketone 2 , we synthesized 5-phenyl substituted pentadienes 1d − f as follows. Luche reduction of 2 gave a 91% yield of carbinol 1d , whose treatment with MOMCl−DIPEA or TBDMSCl-imidazole afforded dienes 1e and 1f in 66% and 67% yields, respectively (Scheme 1). …”
Enantiopure sulfinylnaphthoquinone (+)-5 reacted with racemic acyclic dienes 1a-f bearing a stereogenic allylic center, through a tandem cycloaddition/pyrolytic sulfoxide elimination, to afford optically enriched compounds 8a-f and 9a-f with good like/unlike selectivities (ca. 75:25) and good enantiomeric excesses (68-82%), arising from the partial kinetic resolution of the racemic dienes. The opposite diastereoselection (8g-i: 9g-i, up to 5:95) was observed in reactions with dienes 1g-i, having an additional methyl group at C-3, the enantiomeric purities being moderate (14-25%). Steric effects and torsional interactions in the corresponding approaches account for the observed diastereoselectivities.
“…Starting from known phenylbutadienyl ketone 2 , we synthesized 5-phenyl substituted pentadienes 1d − f as follows. Luche reduction of 2 gave a 91% yield of carbinol 1d , whose treatment with MOMCl−DIPEA or TBDMSCl-imidazole afforded dienes 1e and 1f in 66% and 67% yields, respectively (Scheme 1). …”
Enantiopure sulfinylnaphthoquinone (+)-5 reacted with racemic acyclic dienes 1a-f bearing a stereogenic allylic center, through a tandem cycloaddition/pyrolytic sulfoxide elimination, to afford optically enriched compounds 8a-f and 9a-f with good like/unlike selectivities (ca. 75:25) and good enantiomeric excesses (68-82%), arising from the partial kinetic resolution of the racemic dienes. The opposite diastereoselection (8g-i: 9g-i, up to 5:95) was observed in reactions with dienes 1g-i, having an additional methyl group at C-3, the enantiomeric purities being moderate (14-25%). Steric effects and torsional interactions in the corresponding approaches account for the observed diastereoselectivities.
“…The coupling of 1,3butadienyl-1-magnesium chloride with alkyl bromides or iodides is catalyzed by CuI and proceeds under mild conditions (eq 4). 3 The stereochemistry of the dienyl moiety is retained in the reaction product. The coupling reaction with 5-bromo-2-methyl-1-penten-3-yne was accompanied by allene formation (eq 5).…”
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