Fusao Kido

Stereoselectivity in the sigmatropic rearrangement of eight- and nine-membered cyclic allylsulfonium ylides. synthesis of vinyl- substituted butyro- and valerolactones

Abstract The rhodium (II) acetate-catalyzed [2,3]sigma-tropic rearrangement of the diazo malonates of ( z )-4-phen-ylthio-2-buten-l-ol derivatives 6 afforded vinyl-substituted butyrolactones 10 in a highly stereoselective manner, while the rearrangement of the diazo malonates of homologues, ( z )-5-phenylthio-3-penten-1-ol derivatives 9, yielded vinyl-substituted valerolactones 13 and 14 in the predominance of the formers. A stereochemically fixed substituent R in 9 was found to be an important factor resulting to high stereoselectivity in the latter rearrangement as shown by using diazo malonate 20b as substrate.

Stereoselective synthesis of contiguously substituted butyrolactones based on the cyclic allylsulfonium ylide rearrangement

α-Diazomalonates of (Z)-4-phenylthio-2-buten-1-ol homologues (2) stereoselectively provided γ-alkyl-α-ethoxycarbonyl-α-phenylthio-β-vinylbutyrolactones (1) by the [2.3]sigmatropic rearrangement of cyclic sulfonium ylides (3) intramolecularly generated therefrom with rhodium acetate.

Carbocyclic construction by the [2,3]sigmatropic rearrangement of cyclic sulfonium ylides. a new entry for the stereoselective synthesis of substituted cyclohexanones

Abstract The rhodium(II)-catalyzed cyclization of acyclic α-diazo-β-keto esters 1c,d provided stereoselectively the highly substituted cyclohexanones 3c,d respectively, by the [2,3]sigmatropic rearrangement via stereocontrolled nine-membered allylsulfonium ylides 2c,d. Further elaboration of 3d toward the cyclohexanone 36 accomplished asymmetric formal syntheses of the representative elemanoids, 37 and 38. The compound 3c was transformed into the cyclohexanone 34a and cyclohexene 43, which could serve as the key intermediates for the synthesis of natural products possessing contigously cis-arranged trimethylcyclohexanone and its related moieties, respectively.

New access to dl-paniculide using α-phenylthio-β-vinylbutenolide as synthetic block

Abstract A new synthetic approach to dl -paniculide A (1) based on the annulation of 2-formylpropionate with α-phenylthio-β-vinylbutenolide 4 is described. The annulation products 6a–6c was dehydrated to give 7 , and the sulfoxide of 7 was submitted to sulfoxide-sulfinate rearrangement in aqueous media to yield 8a and 8b . The latter was converted to the former by configurational inversion of its hydroxyl group. Saturated lactone 11a obtained from 8a was homoprenylated, and after desilylation, the product 12b was selenenylated to give 13a . Alkaline hydrolysis followed by oxidative elimination of the selenenyl group provided 14a , which was then acetylated and oxidized with lead tetraacetate to yield 15a and 16a–16c . dl -Paniculide A was derived from 15a and 16a via 18a .

Sesquiterpenoids of vetiver oil—I: The structures of zizanoic acid and related constituents

Abstract Two sesquiterpene car☐ylic acids, zizanoic and epizizanoic acids, were isolated from the essential oil of vetiver and were assigned the structures1a and2a on the basis of chemical degradation. Although khusimol and zizaene (tricyclovetivene) had been assigned structures previously, the current work revealed that these sesquiterpenoids also belong to the zizaane group and that the formulae should be revised as1b and1c, respectively.

An efficient and convenient synthesis of bridged δ-lactones

endo-4-Ethoxycarbonyl-4-(phenylthio)-9-methylene-2-oxabicyclo-[3.3.1]nonan-3-ones (5a–c) and their related compounds 5e–h, endo-4-ethoxycarbonyl-4-(phenylthio)-8-methylene-2-oxabicyclo[3.2.1]octan-3-one (5d) were synthesized from α-diazomalonates 3 of 2-(phenylthio)cyclohex-2-en-1-ols (1a–c) and their related compounds e–h, and 2-(phenylthio)cyclopent-2-en-1-ol (1d), respectively, via the [2,3]sigmatropic rearrangement of cyclic allylsulfonium ylides 4.

An Efficient and Convenient Route to Spiro-fused g-Butyro- and d-Valerolactones

Treatment of the α-diazomalonates (5a-c) of 2-[(2-phenylthiomethyl)-1-cycloalkenyl]ethanols with rhodium acetate led to the [2,3] sigmatropic rearrangement of the cyclic allylsulfonium ylides (6a-c) to give the spiro-fused δ-valerolactones (7a-c) in excellent yields. Similarly, the spiro-fused γ-butyrolactone (10) was prepared starting with the α-diazomalonate of [(2-phenylthiomethyl)-1-cyclohexenyl]methanol analog

Spiroannulation by the [2,3]sigmatropic rearrangement via the cyclic allylsulfonium ylide. A stereoselective synthesis of (+)-acorenone B

A spiroannulation reaction using the [2,3]sigmatropic rearrangement via a cyclic allylsulfonium ylide was developed and applied to the synthesis of (+)-acorenone B starting from (–)-perillaldehyde.

Annelation of 1,3-dicarbonyl compounds with β-vinylbutenolide

With β-vinylbutenolide 2-methylcyclohexane-1,3-dione or 2-ethoxycarbonylcyclohexanone undergoes 1,6-Michael addition and subsequent cyclisation yielding the annelation product.

An Efficient Synthetic Route to g,d-Unsaturated Seven-memberd Lactones

Treatment of the diazomalonates (9a-d) of 2-phenylthio-3-butenol derivatives with catalytic rhodium acetate resulted in the [2,3]sigmatropic rearrangement of six-membered allylsulfonium ylides to provide γ,δ-unsaturated seven-membered lactones (10a-d) in good yields