H. De Koning

Diels-Alder reaction of furan with some dienophiles

Abstract The reaction of furan and maleic acid was carried out in several solvents. The endo-adduct was isolated and the structure established by its spectral properties and conversion into known compounds. The adducts of furan with fumaric acid, diethyl fumarate and diethyl maleate are reported.

Synthesis and some reductions of endo- and exo-3,6-epoxy-Δ4-tetrahydrophthalic anhydride

Abstract The synthesis of endo-3,6-epoxy-Δ4-tetrahydrophthalic anhydride from the endo-adduct of furan and maleic acid is described. Reduction of endo- and exo-3,6-epoxy-Δ4-tetrahydrophthalic anhydride with sodium borohydride gave the corresponding lactones, while catalytic hydrogenation over 10% Pd/C gave anhydride and/or hemi-acylals, depending on the solvent.

Heterocyclic steroids. IV. Total synthesis of some 6-aza-estrogens.

Abstract The syntheses of 6-aza-equilenin, 6-aza-estrone and the corresponding C-17 alcohols have been achieved from N-tosyl-6-aza-8, 14-bisdehydroestrone methyl ether (I). Also available via I are the 14β-isomers of the latter estrogens.

Synthesis of Ethyl 6-Bromosorbate

Abstract Ethyl 6-bromosorbate (1) is a useful intermediate for the preparation of Wittig and Horner-type reagents, which can be used in the synthesis of polyenes with a terminal carboxylic ester function or, as exemplified in recent syntheses of prostaglandins1,2, for the preparation of alkanoic acid derivatives. Allylic bromination of ethyl sorbate following the procedures from literature3,4,5- in our hands resulted in products containing variable amounts of the addition compound ethyl 4,5-dibromo-2-hexenoate. Isolation of pure 1 from this mixture is very difficult6.

Oxygenated γ-Butyrolactones

Abstract In connection with other studies we needed 2-(carboxymethyl)-3-hydroxycyclohexanone lactone 3a. We reasoned that 3a might be obtained from 2-(carboxymethyl)-1,3-cyclohexanedione la via conversion into enol lactone 2a followed by catalytic hydrogenation. Survey of the literature revealed that this approach had already been attempted by Rosenmund et al.2 While their reaction sequence was successful in case of the dimedone derivative lb, which was converted into 2b and 3b, the synthesis failed for la because lactonization with acetyl chloride resulted in the formation of a complex mixture of acylated compounds, which could not be characterized with certainty.