5-MEMBERED, 4-MEMBERED, AND 3-MEMBERED CARBOCYCLIC RINGS FROM 2-DEOXYRIBOSE BY INTRAMOLECULAR NUCLEOPHILIC DISPLACEMENT REACTION

1,3-Dithianes such as 4, 9, 11, 13, and 19 derived from 2-deoxy-D-ribose (1) undergo intramolecular displacement reactions to give three-, four-, and five-membered carbocyclic rings (5, 10, 12, 15, and 20). Cyclopropanes are favored over the cyclobutanes when starting from the epoxides 9 or 11. Treatment of the tosylate 19 gives only a small yield of the corresponding cyclobutane 20, the major product being the ketone 21.