Oxygen heterocycles, literature reviews

Thionyl chloride (SOCl2) is the most versatile of all sulfur transfer reagents in heterocyclic synthesis. The sulfur-oxygen bond renders the sulfur atom more electrophilic the possibility of ready removal by elimination of the oxygen atom allows easy aromatization of many of the initially formed sulfur heterocycles. Two general reviews of the chemistry of thionyl chloride are available.53 Both cover the literature up to about 1970. 

Three-membered heterocycles are invested with a speeial allure that is derived from their apparent simplicity and spartan architecture. Yet these systems are multifaceted, and the literature continues to provide evidence of their diversity, both in terms of preparative routes and subsequent transformations. These smallest of heterocycles also exhibit a synthetically very useful balance between stability and reactivity. Thus, they are often employed as versatile and selective intermediates. With the potential to introduce two adjacent chiral centers with high atom economy, this methodology rightly deserves a place of prominence in synthetic organic chemistry. The utility of epoxides, for example, in the enantioselective synthesis of oxygen-substituted quaternary carbon centers has been the subject of a recent review <04COC 149>. 

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