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Issue 9, 2000
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Stereoselective synthesis of freelingyne and related γ-alkylidenebutenolides [italic v (to differentiate from Times ital nu)]ia vinylogous Mukaiyama aldol additions§

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Abstract

Following the strategy of Scheme 1, a Mukaiyama aldol addition/anti-elimination route to stereopure γ-alkylidenebutenolides 4 was established. The addition giving 27 was only moderately diastereoselective but the products lk- and ul-27 were chromatographically separable (Scheme 4). They underwent highly selective anti-eliminations in the presence of triflic anhydride–pyridine or Burgess' reagent, furnishing the thiophene-containing butenolides Z- and E-28, respectively (Scheme 5). The Mukaiyama aldol addition leading to compound 29 was 100% lk-selective when mediated by BF3 etherate and 87:13 ul-selective in the presence of ZnBr2 (Scheme 6). Stephens–Castro couplings of the resulting butenolides lk- and ul-29 with 3-ethynylfuran proceeded with complete conservation of the stereochemical integrity (Scheme 7). The subsequent anti-eliminations of water were best realized by treatment with DEAD–PPh3. They provided freelingyne (Z-9) with ds=92:8 and its isomer E-9 with ds=98: 2 (Scheme 8). Analogously, the differently substituted (trimethylsiloxy)furans 15 or 16 provided the freelingyne analogs Z-10, E-10 and Z-11 (Schemes 6–8).

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Article information


Submitted
10 Apr 2000
Accepted
30 May 2000
First published
28 Jul 2000

New J. Chem., 2000,24, 659-669
Article type
Paper

Stereoselective synthesis of freelingyne and related γ-alkylidenebutenolides [italic v (to differentiate from Times ital nu)]ia vinylogous Mukaiyama aldol additions

F. von der Ohe and R. Brückner, New J. Chem., 2000, 24, 659
DOI: 10.1039/B002903N

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