[872-36-6] · C3H2O3 · Vinylene Carbonate · (MW 86.05)
Alternate Name: VC; 1,3-dioxol-2-one.
Physical Data: mp 22 °C; bp 165 °C; d 1.36 g cm-3.
Solubility: sol Et2O, benzene.
Form Supplied in: colorless liquid (97%), stabilized with BHT.
Handling, Storage, and Precautions: avoid contact with skin and eyes; do not breathe vapor; cancer-suspect agent. This reagent should only be used in a fume hood.
Since its first synthesis from ethylene carbonate, via a photochemical chlorination-dehydrochlorination sequence (eq 1),1 vinylene carbonate (1) has been widely used in several thermal15 and photochemical reactions.16
Though reputedly a poor dienophile, VC, being a symmetrical dioxygenated alkene, has been frequently employed as a 2p participant in Diels-Alder reactions.2 A [4 + 2] cycloaddition of isobenzofuran and vinylene carbonate takes place under mild conditions and leads to the formation of a highly oxygenated tetrahydronaphthalene (eq 2).3 A thermal reaction between 2,4-dimethylfuran and VC provides a 7:5 mixture of cycloadducts which have been used in the total synthesis of naturally occurring citreoviral (eq 3).4
Whereas vinylene carbonate has been reported to be virtually unreactive towards nitrile oxides,5 its reactivity with other 1,3-dipoles presents appealing syntheses of heterocycles.6 The reaction of VC with hydroximic acid hydrochlorides, for instance, results in the formation of isoxazolines in modest yields (eq 4).7
There are reports that the dipolar cycloaddition reactions of nitrones (both cyclic and open-chain) with VC lead to the formation of mixtures of endo- and exo-adducts.8 However, nitrones bearing a chiral center on the carbon substituent of a nitrone undergo endo additions with achiral dipolarophiles.9 This chemistry leads directly to the formation of masked a-hydroxy aldehydes and presents an attractive route for preparing amino sugars from noncarbohydrate precursors. Thus the [3 + 2] reaction of nitrone (2) and VC leads to a 1:1 diastereomeric mixture of products (both endo) which are readily converted into acylated derivatives of epigentosamines (eq 5).10 A thermal dipolar reaction of an azomethine ylide with VC leads to the formation of highly functionalized pyrrolidines (eq 6).11
Arenes react with VC, under photochemical conditions, to provide meta cycloadducts.12 The photoaddition of VC and anisole provides meta adducts in a 65:35 ratio (endo/exo) and some ortho adducts (~30%) are also observed. The reaction with benzonitrile, however, provides a regioisomeric mix of only endo-meta adducts.13
Humayun S. Ateeq & Fazila Iqbal
H. E. J. Research Institute of Chemistry, Karachi, Pakistan