Ethyl b-Phenylsulfonylpropiolate

[80404-53-1]  · C11H10O4S  · Ethyl b-Phenylsulfonylpropiolate  · (MW 238.28)

(dienophile1,2 used in electrocyclic reactions, such as the Diels-Alder reaction; the adducts can be converted to substituted arenes)

Physical Data: lightly colored oil.

Solubility: sol most organic solvents.

Form Supplied in: prepared and used in situ.1,3

Analysis of Reagent Purity: based on spectral examination.2

Preparative Methods: Schultz and Shen1 reported the first preparation of ethyl b-phenylsulfonylpropiolate (1) which involved m-Chloroperbenzoic Acid oxidation of methyl phenylthiopropiolate (2).4 The latter is prepared from sequential treatment of ethyl propiolate with Lithium Diisopropylamide and phenyl phenylthiosulfonate (eq 1).5 An alternate route to the synthesis of the corresponding methyl and t-butyl ester analogs of (1) has been recently reported.3 Reaction of substituted alkynes with Mercury(II) Chloride and Sodium Benzenesulfinate produces a sulfonylmercury complex which under oxidative demercuriation conditions provides the desired b-phenylsulfonylpropiolate esters in modest yields.

Handling, Storage, and Precautions: undergoes polymerization to a viscous dark substance on standing at rt; refrigeration and short-path silica gel filtration chromatography prior to use is recommended.1

Diels-Alder Reaction.

The reagent is a reactive dienophile; it undergoes essentially quantitative Diels-Alder addition to a variety of dienes including furan, 1,3-cyclohexadiene, and pyrrole (eq 2). Extremely high regioselectivity is observed for the addition of (1) with 1-substituted butadienes.

The synthetic utility of (1) for the preparation of substituted arene systems is exemplified in eq 3. Thus adduct (3) under benzenesulfinic acid elimination conditions provides benzoate (4). On the other hand, simple dehydrogenation of (3) gives aryl sulfone (5) in modest yield.1

Methyl and ethyl b-phenylsulfonylpropiolates have been reported to participate in a [4 + 2] cycloaddition reaction with the vinyl and cross-conjugated porphyrin b,b double bonds of either ring A or B of protoporphyrin IX dimethyl ester in a regio- and stereospecific manner.2 Corey et al., in their total synthesis of forskolin, utilized b-phenylsulfonylpropiolic acid as a dienophile for an intramolecular Diels-Alder reaction, wherein the alkyne unit is tethered to the required diene system through an ester moiety, to build the A/B ring system of the natural product.6

1. Shen, M.; Schultz, A. G. TL 1981, 35, 3347.
2. Pangka, V. S.; Morgan, A. R.; Dolphin, D. JOC 1986, 51, 1094.
3. Rajakumar, P.; Kannan, A. CC 1989, 154.
4. For the use of this reagent as a dienophile and as a ketene equivalent, see: Gupta, I.; Yates, P. CC 1982, 1227.
5. Shine, H. J.; Rahman, M.; Seeger, H.; Wu, G. S. JOC 1967, 32, 1901.
6. Corey, E. J.; Jardine, P. D.; Rohloff, J. C. JACS 1988, 110, 3672.

Neelakautan Balasubramanian & Denis R. St. Laurent

Bristol-Myers Squibb Co., Wallingford, CT, USA

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