Heterocycles form the largest group of organic compounds by far. They are widely found in natural products, drug molecules and organic materials. Extensive efforts have been devoted to develop new and efficient approaches for their synthesis. This thesis mainly describes the synthesis of several five-membered heterocycles via intramolecular oxetane ring opening.

Chapter 1 is an introduction to oxetane ring, mainly including structure features, applications and reported ring-opening reactions of oxetanes.

In Chapter 2, an In-catalyzed intramolecular oxetane ring opening employing Ellman’s N-tert-butanesulfinamides as a chiral auxiliary is disclosed. A range of pyrrolidines bearing an all-carbon quaternary stereocenter at the 3-position was obtained. And finally, the tert-butane...[ Read more ]

Heterocycles form the largest group of organic compounds by far. They are widely found in natural products, drug molecules and organic materials. Extensive efforts have been devoted to develop new and efficient approaches for their synthesis. This thesis mainly describes the synthesis of several five-membered heterocycles via intramolecular oxetane ring opening.

Chapter 1 is an introduction to oxetane ring, mainly including structure features, applications and reported ring-opening reactions of oxetanes.

In Chapter 2, an In-catalyzed intramolecular oxetane ring opening employing Ellman’s N-tert-butanesulfinamides as a chiral auxiliary is disclosed. A range of pyrrolidines bearing an all-carbon quaternary stereocenter at the 3-position was obtained. And finally, the tert-butanesulfinyl auxiliary group could be easily removed.

In Chapter 3, a new asymmetric synthesis of tetrahydrothiophenes has been developed by means of organocatalytic enantioselective desymmetrization of oxetanes accompanied by an acyl transfer. This mild process proceeds with high efficiency and enantioselectivity to establish the quaternary stereocenters. Also, this method can be extended to the synthesis of chiral tetrahydroselenophenes and tetrahydrothiopyrans, which are also highly useful structural units which are difficult to acess due to lacking efficient synthetic methods previously.

In Chapter 4, the first base-promoted oxetane ring opening by secondary phosphine oxide intramolecularly is described. A variety of phospholane oxides bearing an all-carbon quaternary carbon center at the 3-position was obtained. Other than phospholane oxides, six-membered ring phosphinanes and seven-membered ring phosphepanes could also be obtained using this method with excellent diastereoselectivity. Moreover, the phospholane oxides could be easily reduced to phospholanes, which are potential ligands and organocatalysis.

In Chapter 5, the first organobase-catalyzed reaction between CO₂ and oxetane bearing a secondary amino group is developed. Various highly useful oxazolidin-2-ones were obtained with high yields. In comparison with most other reactions involved using CO₂, this method is user friendly with CO₂ used at atmospheric pressure.