THESIS
2018
xviii, 177 pages : illustrations ; 30 cm
Abstract
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...[
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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 CO
2 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 CO
2, this method is user friendly with CO
2 used at
atmospheric pressure.
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