Stereoelectronic control of oxazolidine ring-opening: structural and chemical evidences

Ring opening of oxazolidines derived from tris(hydroxymethyl)aminomethane, l-serine and l-threonine was investigated. It was shown that n(N)→σ ∗(C–O) electron delocalization ( endo-anomeric effect) occurring in the five-membered ring plays a major role in the cleavage of the intracyclic C–O bond. Th...

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Bibliographic Details
Published in:Tetrahedron 2002-11, Vol.58 (47), p.9559-9566
Main Authors: Sélambarom, Jimmy, Monge, Sophie, Carré, Francis, Roque, Jean Pierre, Pavia, André A
Format: Article
Language:English
Subjects:
Chemical Sciences
crystal structure
Organic chemistry
oxazolidines
Polymers
ring-opening
stereoelectronic control
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Summary:Ring opening of oxazolidines derived from tris(hydroxymethyl)aminomethane, l-serine and l-threonine was investigated. It was shown that n(N)→σ ∗(C–O) electron delocalization ( endo-anomeric effect) occurring in the five-membered ring plays a major role in the cleavage of the intracyclic C–O bond. The present work establishes that when the nitrogen lone pair is conjugated with a carbonyl group ( n(N)→π(CO) delocalization) as happens in N-acyloxazolidines, both hydrolysis and reductive ring-opening become much more difficult as a consequence of a concomitant decrease of oxygen basicity and of an increase of the intracyclic C–O bond strength. In A , endo-anomeric effect favours ring-opening, whereas in B reverse motion of electrons makes ring-opening considerably more difficult.
ISSN:0040-4020
1464-5416
DOI:10.1016/S0040-4020(02)01287-5