A Convenient Preparation of Cyclopentane-1,2-Dione

Abstract

Cyclopentane-1,2-dione 1 has been employed as a synthetic intermediate in the preparation of a variety of organic compounds including propellanes^{1a, b}, iso-coumarones², and pyrazines³; moreover, the dione 1 shows some promise⁴ as a potential precursor to the sesquiterpene, modhephene⁵. Most authors who have reported the synthesis of 1 in recent years have used the method of Acheson, who treated 2-bromocyclopentanone with ferric chloride/water⁶ and obtained a 40% yield of 1. We required a more efficient preparation of this material and turned to the bromine oxidation⁷ of the bis-trimethylsilyl ether 2 as a possible alternative. In this regard, diethyl glutarate was cyclized, via the modified acyloin procedure of Bloomfield⁸, to provide excellent yields of the bis-silyl ether 2; however, treatment of this compound with bromine furnished only small amounts