Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    We will mail you new results for this query: keywords==ring closure reactions
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Domino Mukaiyama-Michael reactions in the synthesis of polycyclic systems
Sarabèr, F.C.E. ; Dratch, S. ; Bosselaar, G. ; Jansen, B.J.M. ; Groot, Æ. de - \ 2006
Tetrahedron 62 (2006)8. - ISSN 0040-4020 - p. 1717 - 1725.
silyl enol ethers - catalyzed conjugate addition - vitamin-d-3 northern portion - ring closure reactions - one-pot - acyclic stereoselection - titanium tetrachloride - 2+2+2 construction - carbonyl-compounds - organic-synthesis
Good results were obtained in the Mukaiyama-Michael reaction of the silyl enol ether of cyclohexanone with 2-methyl-2cyclopentenone and carvone, with transfer of the silyl group to the receiving enone and with TrSbCl6 as catalyst. A second Mukaiyama-Michael reaction of this new silyl enol ether with methyl vinyl ketone and cyclization of the resulting adduct leads to tricyclic compounds in one-pot domino sequences. The scope and limitations of this domino reaction have been investigated.
New approaches toward the synthesis of (D-homo) steroid skeletons using Mukaiyama reactions
Sarabèr, F.C.E. ; Baranovsky, A. ; Jansen, B.J.M. ; Posthumus, M.A. ; Groot, Æ. de - \ 2006
Tetrahedron 62 (2006)8. - ISSN 0040-4020 - p. 1726 - 1742.
(+)-9(11)-dehydroestrone methyl-ether - vitamin-d-3 northern portion - optically-active steroids - ring closure reactions - claisen-ene strategy - conjugate addition - one-pot - alpha,beta-unsaturated ketones - enantioselective synthesis - 2+2+2 construction
New, short, and flexible procedures have been developed for syntheses of steroid and D-homo steroid skeletons. A Mukaiyama reaction between the silyl enol ether of 6-methoxytetralone and 2-methyl-2-cyclopentenone or carvone, with transfer of the silyl group to the receiving enone, gave a second silyl enol ether. Addition of a carbocation, generated under Lewis acid conditions from 3-methoxy-2-butenol, 3-ethoxy-3-phenyl-2-propenol or 3-methoxy-2-propenol to this second silyl enol ether gave adducts, which could not be cyclized by aldol condensation to (D-homo) steroid skeletons. The Mukaiyama-Michael reaction of the silyl enol ether of 6-methoxy tetralone with 2-methyl-2-cylopentenone gave a second silyl enol ether, which reacted in high yield with a carbocation generated from 3-hydroxy-3-(4-methoxyphenyl)propene. Ozonolysis of the double bond in this adduct gave a tricarbonyl compound (Zieglers triketone), which has been used before in the synthesis of 9, 11-dehydroestrone methyl ether. A second synthesis of C17 substituted CD-trans coupled (D-homo) steroid skeletons has been developed via addition of a carbocation, generated with ZnBr2 front a Torgov reagent, to a silyl enol ether containing ring D precursor. The obtained seco steroids have been cyclized under formation of the 8-14 bond by treatment with acid. The double bonds in one of the cyclized products have been reduced to a C17-substituted all trans steroid skeleton.
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